Geophysical Logging and Imaging of Drillholes OL-KR56, OL-KR57 and OL-KR57B at Olkiluoto in

Transkriptio

1 Working Report Geophysical Logging and Imaging of Drillholes OL-KR56, OL-KR57 and OL-KR57B at Olkiluoto in Karla Tiensuu, Eero Heikkinen, Ida Ravimo, Risto Kiuru June 2017 POSIVA OY Olkiluoto FI EURAJOKI, FINLAND Phone (02) (nat.), ( ) (int.) Fax (02) (nat.), ( ) (int.)

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3 Working Report Geophysical Logging and Imaging of Drillholes OL-KR56, OL-KR57 and OL-KR57B at Olkiluoto in Karla Tiensuu, Eero Heikkinen, Ida Ravimo, Risto Kiuru Pöyry Finland Oy June 2017 Working Reports contain information on work in progress or pending completion.

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5 ABSTRACT Geophysical logging and imaging were conducted in drillholes OL-KR56, OL-KR57 and OL-KR57B during Drillhole OL-KR56 is 1200 m, OL-KR m and OL-KR57B 45 m long. Measurements were done by Suomen Malmi Oy. Quality control, processing and reporting were carried out by Pöyry Finland Oy. This report describes the measurements, data processing and results. Measurements included optical and acoustic imaging and geophysical logging of natural gamma radiation, gamma-gamma density, magnetic susceptibility, dual laterolog resistivity, full waveform sonic, mechanic caliper and fluid resistivity and temperature. Data processing included depth matching to core logging, orienting of images and computing of caliper from acoustic imaging data. Processing of geophysical data included calculating physical properties, presenting natural gamma, gamma-gamma density, susceptibility and resistivity. P and S wave velocities and amplitudes, tubewave energies and waveform attenuations were computed. Rock mechanic parameters were computed. Acoustic televiewer images showed indications of breakout features in OL-KR56. Acoustic imaging was repeated in order to monitor possible changes in drillhole wall. Significant changes were not observed in two years period. Mechanic caliper and caliper from acoustic imaging provide comparable results, though acoustic televiewer produced caliper is more sensitive and accurate. A two-channel and a four-channel full waveform sonic probes and interpretation of their data were compared in OL-KR56. Interpretation provided comparable results both with first arrival picking (two-channel data) and semblance analysis (four-channel). Semblance analysis can produce more reliable velocity data when petrophysical velocity reference is not available, and fluid velocity cannot be approximated with constant value. Resistivity logging using normal array was measured in OL-KR56 to compare normal array and focused laterolog resistivities. Both methods provide similar general level of resistivity when normal resistivity is corrected for fluid resistivity. Focused dual laterolog requires drillhole fluid correction only at very low fluid resistivities. Keywords: geophysics, drillhole logging, drillhole imaging, bedrock characterization, spent nuclear fuel disposal, method comparison, full waveform sonic, resistivity, caliper.

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7 GEOFYSIKAALISET KAIRAREIKÄMITTAUKSET JA KUVAUKSET KAIRA- REI ISSÄ OL-KR56, OL-KR57 JA OL-KR57B OLKILUODOSSA VUOSINA TIIVISTELMÄ Kairarei issä OL-KR56, OL-KR57 ja OL-KR57B tehtiin geofysikaalisia reikämittauksia ja kuvauksia vuosina Kairareikä OL-KR56 on 1200 m, OL-KR m ja OL-KR57B 45 m pitkä. Mittaukset teki Suomen Malmi Oy. Laadunvalvonnan, aineistonkäsittelyn ja raportoinnin hoiti Pöyry Finland Oy. Tässä raportissa käsitellään mittauksia, aineistonkäsittelyä ja tuloksia. Kairarei issä tehtiin optinen ja akustinen kuvaus ja mitattiin luonnongammasäteily, tiheys, magneettinen suskeptibiliteetti, kallioperän ominaisvastus, akustinen kokoaallonmuoto, reikähalkaisija ja reikäveden ominaisvastus ja lämpötila. Aineistonkäsittelyssä mittaustulosten syvyystiedot korjattiin vastaamaan kairasydänkartoitusta. Reikäkuvat suunnattiin ja akustisista kuvista laskettiin kairareikien halkaisijat. Geofysikaalisesta mittausaineistosta määritettiin fysikaaliset ominaisuudet kuten luonnongammasäteily, tiheys, suskeptibiliteetti ja ominaisvastus. P- ja S-aallonnopeudet ja amplitudit sekä putkiaaltoenergiat määritettiin ja aaltojen vaimenemiset laskettiin. Kalliomekaaniset parametrit määritettiin. Kairareiän OL-KR56 akustisissa kuvissa havaittiin merkkejä breakout-muutoksista. Kuvaus uusittiin tarkoituksena seurata mahdollisia muutoksia kairareiän seinämillä. Kahden vuoden tarkastelujaksolla ei havaittu merkittäviä muutoksia. Akustisesta kuvaaineistosta laskettua ja mekaanisesti määritettyä reikähalkaisijaa vertailtiin. Tulokset vastasivat toisiaan, joskin akustisesti määritetty tieto oli tarkempaa ja yksityiskohtaisempaa. Nelikanavaista akustisen kokoaallonmuodon mittausta kokeiltiin kairareiässä OL-KR56 tarkoituksena vertailla kaksikanavaisen ja nelikanavaisen mittausaineiston käsittelyä ja tuloksia. Käsittelyssä verrattiin ensisaapujien poimintaan (kaksikanavainen aineisto) ja ns. semblance-analyysiin (nelikanavainen aineisto) perustuvaa tulkintaa. Semblanceanalyysilla voidaan määrittää aallonnopeudet varmemmin, erityisesti mikäli petrofysikaalista vertailuaineistoa ei ole käytettävissä eikä reikäveden akustista nopeutta voida pitää vakiona. Kallioperän ominaisvastuksen mittauksissa verrattiin normaalijärjestelmää ja fokusoivaa ominaisvastusmittausta. Normaalijärjestelmällä mitattu ominaisvastus on reikäveden ominaisvastuksella korjattuna samalla tasolla kuin fokusoivan ominaisvastusmittauksen tulos. Fokusoivan ominaisvastusmittauksen tuloksiin tarvitaan vastaava korjaus vain reikäveden ominaisvastuksen ollessa hyvin pieni. Avainsanat: geofysiikka, kairareikämittaukset, kairareikäkuvaukset, kallioperän karakterisointi, käytetyn ydinpolttoaineen loppusijoitus, menetelmävertailu, akustinen kokoaallonmuoto, ominaisvastus, reikähalkaisija.

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9 1 TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ 1 GENERAL EQUIPMENT AND METHODS Geovista Slimhole Density Probe ALT QL40 GR Natural Gamma Probe QL40 MagSus Magnetic Susceptibility Probe Resistivity Probes Geovista Dual Guard Focused Resistivity Probe Geovista QL40 ELOG IP Normal Resistivity Probe Full Waveform Sonic Tools ALT FWS50 Full Waveform Sonic Tool ALT QL40 FWSS Full Waveform Sonic Tool ALT OBI40 Slimhole Optical Televiewer ALT ABI40 Slimhole Acoustic Televiewer Mount Sopris Caliper Probe Mount Sopris Fluid Resistivity and Temperature Probe FIELD WORK PROCESSING AND RESULTS Natural gamma radiation Geovista slimhole density probe ALT QL40 GR Natural gamma probe Natural gamma radiation results Gamma-gamma density Magnetic susceptibility Resistivity surveys Focused resistivity Normal resistivity and induced polarization Full Waveform Sonic ALT FWS50 Full Waveform Sonic processing ALT QL40 FWSS Full Waveform Sonic processing Full waveform sonic results Optical drillhole image Acoustic drillhole image Caliper Mechanical caliper measurements Fluid resistivity and temperature COMPARISON OF EQUIPMENT AND DATA IN OL-KR Resistivity measurements Focused Resistivity ELOG IP Normal Resistivity Comparison of resistivity measurements Comparison of full wave form sonic measurements ALT FWS ALT QL40 FWSS Comparison Comparison of mechanical and ABI caliper Fluid resistivity and temperature CONCLUSIONS REFERENCES APPENDICES... 63

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11 3 1 GENERAL Suomen Malmi Oy (Smoy) carried out geophysical drillhole surveys of drillholes OL- KR56, OL-KR57 and OL-KR57B for Posiva Oy in November and December 2012 and in January and February In addition to this, OL-KR56 was included in a survey programme in , and acoustic imaging, electrical normal logging as well as full waveform sonic measurements were executed in order to create data for comparison of older and new material. This material is also included in this report as well as some comparison of different equipment. Because of meaningful comparison of equipment and methods the processing and results from full waveform sonic and electrical surveys are described more detailed than other methods. The assignment included optical and acoustic imaging, geophysical surveys as well as data interpretation according to purchase orders , and The investigations contribute the detailed fracture detection and orientation as well as further description of the crystalline bedrock. Field work was coordinated by geophysicists Anna-Maria Tarvainen ( ) and Karla Tiensuu ( ) and by geophysical foreman Antero Saukko. Quality control of raw data, interpretation as well as data integration was done by Pöyry Finland Oy. Reporting was conducted by geophysicist Karla Tiensuu. This report describes the field operation of drillhole surveys, as well as the data processing and the interpretation. The quality of the results is shortly analysed and the data presented in the Appendices B-1 B-12 (drillhole OL-KR56), C-1 C-6 (drillhole OL-KR57) and D-1 D-6 (drillhole OL-KR57B). Appendices E-1 E-11 are the data sheets of used equipment. Appendix A presents the lithological dictionary used in the geophysical data sheets in Appendices B D.

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13 5 2 EQUIPMENT AND METHODS The geophysical survey carried out in drillholes OL-KR56, OL-KR57 and OL-KR57B included natural gamma radiation, gamma-gamma density, magnetic susceptibility, focused resistivity and full waveform sonic measurements as well as optical and acoustic imaging, drillhole caliper, and fluid resistivity and temperature measurements. Additional induced polarisation (IP) and resistivity calibration test surveys were done in drillhole OL-KR56. In OL-KR56 acoustic imaging and normal resistivity measurement were re-measured from the full drillhole length and full waveform sonic measurement was partly repeated. The used methods, acquisition systems and probes are listed in Table 2-1. Timing of different measurements is shown in Tables The used survey parameters are listed in Table 3-6. Data sheets of the probes are attached as Appendices E-1 E-11. Table 2-1: Methods, acquisition system and probes used. Data sheets of the probes are attached as Appendices E-1 E-11. Method Acquisition Probe Appendix Gamma-gamma density ALT Matrix Geovista Slimhole Density Probe E-1 Natural gamma radiation ALT Matrix Geovista Slimhole Density Probe E-1 Natural gamma radiation ALT Matrix ALT QL40 GR Natural Gamma Probe E-2 Magnetic susceptibility ALT Matrix ALT QL40 MagSus Probe E-3 Focused resistivity ALT Matrix Geovista Dual Guard Focused Resistivity Probe (DLL3) E-4 Induced polarisation and Geovista QL40 ELOG IP Normal ALT Matrix resistivity Resistivity Probe E-5 Full waveform sonic ALT Matrix ALT FWS50 (2013) E-6 Full waveform sonic ALT Matrix ALT QL40 FWSS (2014) E-7 Optical imaging ALT Matrix ALT OBI40 E-8 Acoustic imaging ALT Matrix ALT ABI40 E-9 Caliper, mechanical ALT Matrix Mount Sopris 3-Arm Caliper Probe E-10 Fluid resistivity and temperature ALT Matrix Mount Sopris Temperature-Fluid Resistivity Probe E-11 The cable was operated by a motorised winch. Depth measurement was triggered by pulses of a sensitive depth encoder, installed on a pulley wheel. A 3/16 steel reinforced 4-conductor cable manufactured by Mount Sopris Instrument was used in the logging. The cable was marked with 10 m intervals for controlling depth measurement to adjust any cable slip and stretch. 2.1 Geovista Slimhole Density Probe Gamma-gamma density and natural gamma radiation were measured with an integrated Geovista slimhole density probe. Survey data is obtained from same depth values in a single run. The probe uses a 10 mci cesium source. The probe measures simultaneously the natural gamma radiation over 134 cm and two gamma-gamma counts over different distances from detector (short spacing density, SSD, 11 cm and long spacing density,

14 6 LSD, 22 cm). Detectors are 50 x 25 mm NaI crystals. Recording time is 0.22 second. Density probe has a diameter of 38 mm and a length of 1.65 m. Technical information of equipment is presented in Appendix E ALT QL40 GR Natural Gamma Probe Natural gamma radiation was measured also with ALT s QL40 GR stackable natural gamma probe together with normal resistivity logging. Resistivity and natural gamma data were obtained from same depth values in a single run. The purpose for the use of QL40 GR probe was to have natural gamma data as support for resistivity logging s depth matching. Measurement interval is 0.05 m. Detector is a NaI crystal of 1 * 3 (25 * 75 mm). Probe diameter is 40 mm and length 0.9 m. Technical information of equipment is presented in Appendix E QL40 MagSus Magnetic Susceptibility Probe Magnetic susceptibility was measured with ALT s QL40 MagSus magnetic susceptibility probe with Bartington s sensors in it. The probe has two sections: the focused dual coil detector is located in a non-magnetic enclosure and electronic circuitry in an aluminium alloy cylindrical enclosure. The probe uses operating frequency of 1.5 khz. The full width half maximum of the vertical magnetic zone of investigation is 120 mm. Susceptibility probe has a diameter of 43 mm and a length of 1.4 m. Technical information of equipment is presented in Appendix E Resistivity Probes Resistivity measurements were done with two different probes and methods, with Geovista s Dual Guard Focused Resistivity probe (DLL3) and Geovista s Normal Resistivity probe (QL40 ELOG IP), which are presented in sections and 2.4.2, respectively Geovista Dual Guard Focused Resistivity Probe Focused resistivity measurements were carried out using Geovista s Dual Guard (DLL3) focused resistivity probe. The probe was non-centralised. It measures shallow and deep laterolog resistivity and offers deeper penetration and better vertical resolution than the traditional normal resistivity probe. Current is injected onto a plane perpendicular to drillhole, using two symmetrically placed A-current electrodes at different distances (70 cm and 110 cm from the center of the probe). Width of each current electrode is 20 cm. Both electrodes are connected to same electrical current pole. Return current is arranged on isolator bridle which is 10 m apart of active electrode array. Potential difference is measured between two voltage electrodes at 20 cm distance from each other, centered at the center point of active current electrodes. Level of injected current is depending on conductivity of the bedrock. Received voltage is also inversely

15 7 proportional to conductivity. Both voltage and current are measured. Ratio of voltage to current (resistance) is used together with geometric coefficient to obtain bedrock resistivity. Tool resistivity readings were calibrated with measuring the resistance of known calibration pad at 1 Ωm, 10 Ωm, 100 Ωm and 1000 Ωm. The tool has a diameter of 42 mm and a length of 2.37 m. Technical information of equipment is presented in Appendix E Geovista QL40 ELOG IP Normal Resistivity Probe Induced polarization and short and long normal resistivity measurements were performed with Geovista s Normal resistivity ELOG probe (QL40 ELOG IP). The probe was non-centralized and the natural gamma measurement was done simultaneously with ALT QL40 GR probe in 2015 s survey. The ELOG tool is feeding current at four different distances from resistivity measurement (SPR) electrode which was at the bottom of the probe. The distances to active current grounding are 8, 16, 32 and 64. Return current is fed to an electrode at a top of isolator bridle, 12.4 m above tool connector GO4.There is also a possibility to measure single point resistance (SPR) with this probe. SPR log records the electrical resistance from points within the borehole to an electrical ground at land. Normal resistivity array is effectively a pole-pole array with two active electrodes. Voltage was measured between the active voltage electrode (SPR) and the return electrode connected in half-distance of the isolator bridle (6 m above the probe connector GO4). Ratio of the voltage to current is computed to apparent resistivity using a simple geometric factor for pole-pole array. Induced polarization is measured with 16 and 64 normal array, producing both voltage decay curves up to 2 seconds (500 ms time window was used), and secondary to primary voltage ratios for ten different time channels (mv/v). Results are also computed to generic IP chargeability value, Ma (ms). The probe is compatible with ALT acquisition system. Measuring range is modified from the original 0 10,000 Ωm to 0 40,000 Ωm. Probe diameter is 42 mm. The probe does not contain electrically conductive parts, except a voltage return in the middle of a 12 m insulator bridle, and the current return is grounded on a steel armoured cable and a cable connector. Connectors have to be carefully insulated with for example tape or heat-shrinkable tube before measurement. Cable connector was attached to fixed electrode position when located out of drillhole at 0 12 m drillhole length. Reading accuracy is better than 1 Ω or 1 Ωm. Single point resistance and short normal can measure a full range of resistivity. The long normal displays occasionally a cut-off of low resistivities at frequency alternating conductive zones (a short circuit through conductive layers). In sparsely fractured rock the resistivity is high, decreasing slightly due to saline water in bedrock and in drillhole deeper down. Resistivity decreases in zones of intense alteration or deformation, and is generally low at zones of high fracture frequency, and narrow sulphide or graphite bearing bands. Technical information of the tool is presented in Appendix E-5.

16 8 2.5 Full Waveform Sonic Tools Full waveform sonic measurements were done with two different equipment. Drillholes OL-KR56, OL-KR57 and OL-KR57B were measured with Advanced Logic Technology s (ALT) FWS50 probe in 2012 and 2013 and drillhole OL-KR56 was resurveyed with ALT QL40 FWSS probe in 2014 between depth interval m. The probes were centralized in the drillholes, primarily with rigid plastic centralizers. However, in the end part of drillhole OL-KR56 the probe with plastic centralizers did not pass through the depth 1100 m, and therefore the depth m was measured with bow spring centralizers ALT FWS50 Full Waveform Sonic Tool A piezoceramic transmitter (Tx) emits sonic impulses of 15 khz nominal frequency and two receivers (Rx1 and Rx2) detect arriving impulses and record the waveform. The arriving waveform is digitally sampled according to tool configuration parameters. Tx- Rx spacing is 0.60 m (Rx1) and 1.00 m (Rx2). Tool diameter is 50 mm. Technical information of FWS50 equipment is presented in Appendix E ALT QL40 FWSS Full Waveform Sonic Tool A piezoceramic transmitter (Tx) emits sonic pulses of 15 khz nominal frequency and four receivers (Rx1 Rx4) detect arriving impulses and record the waveform. The arriving waveform is digitally sampled according to tool configuration parameters. Tx- Rx spacing is 0.60 m (Rx1), 0.80 m (Rx2), 1.00 m (Rx3) and 1.20 m (Rx4). Tool diameter is 50 mm. Technical information of QL40 FWSS equipment is presented in Appendix E ALT OBI40 Slimhole Optical Televiewer Optical imaging was carried out using Advanced Logic Technology s (ALT) OBI40 optical televiewer. OBI40 is a high-resolution optical drillhole imagery for wells and drillholes. OBI40 creates a 360 degree image of drillhole wall by using a CCD camera with a conic prism. Tool orientation is controlled with measurements of a 3-axes magnetometer and 3 accelerometers. This makes it possible to measure drillhole deviation data and create accurate orientation of the optical image. OBI40 tool diameter is 40 mm. Tool azimuthal resolution is user definable (90, 180, 360 or 720 pixels per revolution). Vertical resolution depends on sampling rate and maximum resolution is 0.5 mm. Smoy had prepared special centralisers for 76 mm drillholes. Tool technical information of OBI40 equipment is presented in Appendix E ALT ABI40 Slimhole Acoustic Televiewer Acoustic imaging was carried out using Advanced Logic Technology s (ALT) ABI40 acoustic drillhole televiewer. ABI40 creates a 360 degree image of drillhole wall by using acoustic ultrasound pulses and recordings of amplitude and travel time of signal. Drillhole caliper can be calculated from the travel time data. Tool orientation is controlled with measurements of a 3-axes magnetometer and 3 accelerometers. This makes it possible to measure drillhole deviation data and create accurate orientation of the acoustic image.

17 9 ABI40 tool diameter is 40 mm. Width of acoustic beam is 1.5 mm. The sampling rate is 72, 144 or 288 measured points per tool s acoustic head revolution depending on the operator s selection. Both longitudinal and azimuthal resolution is restricted by width of acoustic beam, i.e. 1.5 mm, although also smaller features can be detected. The detection limit for structures is at order of tens of micrometers. Smoy had prepared special centralisers for 76 mm drillholes. Two different individual tools were used in different survey runs, but there were only minor differences in tool operating log files concerning for example time sampling and slightly affecting processing. Tool technical information of ABI40 equipment is presented in Appendix E Mount Sopris Caliper Probe Mechanical caliper measurements were carried out with 2PCA Arm Caliper probe manufactured by Mount Sopris Instrument, with one arm connected. The probe is compatible with ALT acquisition system. Tool technical information is presented in Appendix E Mount Sopris Fluid Resistivity and Temperature Probe Fluid resistivity and temperature measurements were carried out with a probe manufactured by Mount Sopris Instrument. The probe is compatible with ALT acquisition system. Tool technical information is presented in Appendix E-11.

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19 11 3 FIELD WORK The field work was carried out within 21 working days, in November and December 2012 and in January and February The assignment consisted of 1645 m of drillhole surveys in three drillholes, OL-KR56, OL-KR57 and OL-KR57B. In addition to this, 1101 m of acoustic imaging and 504 m of full waveform sonic measurements were repeated in drillhole OL-KR56 in December Resistivity data (normal resistivity ELOG ) from the first survey run suffered severe quality problems in drillhole OL-KR56, possibly due to electrical disturbance. Therefore it was re-measured with ALT QL40 ELOG IP probe in 20 th of May Fluid resistivity and temperature were measured for level correction of ELOG data in 5 th 6 th of May 2015 using Posiva Flow Log tool. Additionally, this data could be used also in comparison purposes, discussed in more details later in the section 5. Re-measurement of acoustic imaging was planned in order to improve image quality and to check whether the initially observed drillhole breakout would be changing during time. Full wave form sonic was re-measured partly for comparison purposes. The first survey run in 2012 was done with a probe having two receivers and the rerun in 2014 was done with a probe with four receivers. The data from the first run was also suffering some quality problems, which was another motivation for re-measurements. Drillhole specifications are listed in Table 3-1 as they are in POTTI database. It s worth noticing that according to fracture logging and imaging data it seems that casing depth for OL-KR57B should be 3.89 m instead of 3.95 m as it is stated in POTTI. Casing depth 3.89 m is used in this report and relative data processing. Performed surveys in each drillhole are listed in Table 3-2 and timing and the crew of the field work in Tables 3-3, 3-4 and 3-5. Table 3-6 shows survey parameters for each method. Table 3-1: OL-KR56, OL-KR57 and OL-KR57B drillhole specifications. Coordinates and directions are for starting situation.(*) Casing depth for drillhole OL-KR57B is stated 3.95 m in POTTI, but it seems that it should be 3.89 m, which is used in this report. OL-KR56 OL-KR57 OL-KR57B Northing Easting Elevation (m) Casing depth (m) /3.89(*) Diameter (mm) Azimuth ( ) Dip ( ) Length (m)

20 12 Table 3-2: Performed measurements in each drillhole. Method OL-KR56 OL-KR57 OL-KR57B Natural gamma radiation and gamma-gamma density (Geovista Slimhole density and natural gamma) Natural gamma radiation (ALT QL40 GR) Resistivity and IP (ALT QL40 ELOG IP) x x x Susceptibility (ALT QL40 MagSus) x x x Focused resistivity ( Geovista DLL3) x x x Full waveform sonic (ALT FWS50) x x x Full waveform sonic (ALT QL40 FWSS) Optical imaging (ALT OBI40) x x x Acoustic imaging (ALT ABI40) x x x Caliper (mechanical), (Mount Sopris 3-Arm Caliper) x x x Fluid resistivity and temperature (Mount Sopris Temperature-Fluid Resistivity) Fluid resistivity and temperature (Posiva Flow Log) x x x x x x x Table 3-3: Tasking of the field work in drillhole OL-KR56. Crew in geophysics and imaging (Smoy): JH = Jari Hakkarainen, AK = Arto Kumpulainen, HL = Henri Luiro, PM = Petri Mäklin, JN = Jukka Niinimäki, UP = Urmas Peltovuoma, AS = Antero Saukko, HY = Heikki Ylilauri. Crew for PFL survey (Pöyry Finland): KR = Kyösti Ripatti. Date Drillhole Actions Surveyors OL-KR56 Optical imaging HL OL-KR56 Optical imaging AK, JN, HL OL-KR56 Susceptibility AS, HL OL-KR OL-KR56 Natural gamma radiation and gammagamma density Natural gamma radiation and gammagamma density, focused resistivity (DLL3), full waveform sonic (FWS50) HL HL, AK, JN, JH, PM OL-KR56 Acoustic imaging, caliper AK, UP, PM, JN OL-KR56 Fluid resistivity and temperature, acoustic imaging OL-KR56 Resistivity (QL40 ELOG IP), IP AS AK, UP, PM, JN OL-KR56 Full waveform sonic (QL40 FWSS) AS, HL, HY OL-KR56 Acoustic imaging AS, HY OL-KR OL-KR56 Fluid resistivity and temperature, Posiva Flow Log Resistivity (QL40 ELOG IP), natural gamma radiation (QL40 GR) KR PM

21 13 Table 3-4: Tasking of the field work in drillhole OL-KR57. Crew: AK = Arto Kumpulainen, HL = Henri Luiro, PM = Petri Mäklin, JN = Jukka Niinimäki, UP = Urmas Peltovuoma. Date Drillhole Actions Surveyors OL-KR57 Optical imaging HL OL-KR OL-KR57 Full waveform sonic (FWS50), optical imaging Susceptibility, focused resistivity, gamma-gamma density and natural gamma radiation OL-KR57 Fluid resistivity and temperature HL HL, AK HL, JN OL-KR57 Caliper, acoustic imaging AK, UP OL-KR57 Caliper, fluid resistivity and temperature PM, JN Table 3-5: Tasking of the field work in drillhole OL-KR57B. Crew: HL = Henri Luiro, AK = Arto Kumpulainen, JN = Jukka Niinimäki, PM = Petri Mäklin, UP = Urmas Peltovuoma. Date Drillhole Actions Surveyors OL-KR57B Optical imaging HL OL-KR57B Susceptibility, gamma-gamma density, natural gamma radiation, focused resistivity, full waveform sonic (FWS50) OL-KR57B Fluid resistivity and temperature HL AK, JN OL-KR57B Caliper AK, UP, PM, JN OL-KR57B Acoustic imaging AK, UP

22 14 Table 3-6: Survey parameters of the applied methods. Method Natural gamma and gamma-gamma density (Geovista Slimhole density and natural gamma) Natural gamma radiation (ALT QL40 GR) Induced polarisation and resistivity (ALT QL40 ELOG IP) Susceptibility (ALT QL40 MagSus) Focused resistivity (Geovista DLL3) Full waveform sonic (ALT FWS50) Full waveform sonic (ALT QL40 FWSS) Depth sampling 0.02 m Settings and calibrations Survey Tool calibrated by the manufacturer, data calibrated with time-dependent toolspecific calibration speed 2.0 m/min 0.05 m Tool calibrated by the manufacturer 2.0 m/min 0.05 m 0.02 m 0.02 m 0.02 m 0.02 m Calibration tested with resistors and used in recalculation, final results calibrated with fluid resistivity data from Posiva Flow Log Calibration measurent with calibration brick Calibrated with measuring the resistance of known calibration pad Time sampling 2 µs, 1024 samples, time interval µs, R1 gain 1, R2 gain 1 Downwards: Time sampling 4 µs, 1024 samples, time interval µs, 4 channels (Rx1-Rx4) Upwards: Time sampling 20 µs, 800 samples, time interval 0 16 ms, one channel (Rx3 = 1.00 m) 2.0 m/min 2.0 m/min 2.0 m/min 1.0 m/min 1.0 m/min Optical imaging (ALT OBI40) m 720 pixels / turn, 0.5 mm depth interval 0.3 m/min Acoustic imaging (ALT 288 measured points per revolution, m ABI40) mm depth interval 0.8 m/min Caliper (Mount Sopris 3- Arm Caliper) 0.01 m Calibrated with rings 1.0 m/min Fluid resistivity and Calibrated for temperature using Pt-1000 temperature (Mount 0.05 m thermometer, and for fluid resistivity with Sopris Temperature-Fluid known NaCl solutions and temperature Resistivity) 3.0 m/min Fluid resistivity and Calibrated for temperature and resistivity temperature (Posiva 0.07 using procedures documented in Flow Log), used as 0.08 m respective survey memorandum reference 1.0 m/min

23 15 4 PROCESSING AND RESULTS The processing of the conventional geophysical results includes basic corrections and calibrations presented in Posiva Working report (Lahti et al., 2001). Sonic interpretations, depth adjustments and data integration were carried out by Pöyry Finland Oy (Eero Heikkinen) as described in Heikkinen et al. (2005). Natural gamma radiation, gamma-gamma density, magnetic susceptibility and focused resistivity (laterolog results are presented in Appendices B-1, C-1 and D-1. Resistivity results from both laterolog and normal resistivity surveys are presented in Appendix B- 2. The full waveform sonic results, both images and calculated rock mechanical parameters, are shown in Appendices B-3 B-9, C-2, C-3, D-2 and D-3. Fluid properties are presented in Appendices B-12, C-4 and D-4. The results were combined with the available geological data received from Posiva. The data includes lithology, fracture frequency, fracture location and core loss. Mechanical caliper results are presented in Appendices B-1, C-1 and D-1. Optical and acoustic televiewer images are presented in Appendices B-10, B-11, C-5, C-6, D-5 and D-6. Acoustic televiewer images include also caliper data calculated from acoustic televiewer s travel time data. Fluid resistivity and temperature results are presented in Appendices B-12, C-4 and D-4. Results from IP and resistivity (Elog) reference surveys in drillhole OL-KR56 are presented in Appendix B-2. The initial depth matching was done as described in Heikkinen et al. (2016). Depth accuracy to core depth of imaging data is 2 cm and of all other methods 5 10 cm. 4.1 Natural gamma radiation Gamma ray intensity was measured both with Geovista slimhole density probe and with ALT QL40 GR probe which was stacked with resistivity (ALT QL40 ELOG IP) probe during drillhole run. Production survey in was done with Geovista s slimhole density probe, and for depth matching purposes the stackable ALT QL40 GR probe was used together with normal array resistivity logging. The data from ALT QL40 GR probe was processed to the same level than data measured with Geovista Slimhole Density probe, processing done as described in Heikkinen et al. (2016). The QL40 GR data was used as final results as it has better quality than slimhole data does Geovista slimhole density probe Geovista s probe has been calibrated by comparing the readings with previous WellMac survey, run overlapping in deep drillholes ONK-KR54 and ONK-KR55 (Tarvainen & Heikkinen, 2011). The microröntgen per hour (µr/h) values computed from counts per second (cps) of Geovista density probe's gamma sensor have been calibrated by comparing the readings to those of old WellMac tool which has been calibrated for reading in rapakivi granite (Laurila et al. 1999). The same numeric level in microröntgens per hour (μr/h) is obtained by multiplying the cps values provided by Geovista s probe by factor Natural gamma counts of Geovista s slimhole density

24 16 probe are enhanced by larger NaI crystal but reduced by shorter counting time which makes the gamma ray values slightly noisier compared to those of WellMac tool ALT QL40 GR Natural gamma probe ALT s QL40 GR natural gamma results were calculated to µr/h values and the same level than achieved with Geovista s slimhole density probe as described in Heikkinen et al. (2016). The equations ( ) used are shown below. Converting the counts to cps: IQL40 = XQL40 / t (4-1), where IQL40 = gamma ray intensity measured with ALT QL40 GR probe (cps), XQL40 = measured counts from ALT QL40 GR probe and t = counting time (s). Adjusting the cps level to similar than the one measured with Geovista s slimhole density probe: IScaleGeovista = * IQL (4-2), where IScaleGeovista = gamma ray intensity (cps) scaled to the same level than data measured with Geovista probe, = multiplication factor ((Slimhole cps median/ql40 cps median) * (Slimhole cps standard deviation/ql40 cps standard deviation)), IQL40 = gamma ray intensity (cps) measured with ALT QL40 GR probe and = difference of cps medians ((standard deviation*cps median) cps median). Finally the cps values measured with QL40 GR probe were converted to µr/h values: X = * IScaleGeovista (4-3), where X = exposure of gamma radiation (µr/h), = multiplication factor scaling Geovista data to µ/h values and IScaleGeovista = gamma ray intensity (cps) measured with ALT QL40 GR and scaled to Geovista probe data level.

25 Natural gamma radiation results The natural gamma radiation results are presented in Appendices B-1, C-1 and D-1, and the range also briefly in Table 4-1. Table 4-1: The range of the natural gamma radiation survey results below the casing depths. Slimhole and QL40 GR are meaning Geovista s slimhole density probe and stackable ALT s QL40 GR natural gamma radiation probe, respectively. Probe Drillhole Depth interval (m) Range (µr/h) min max min max median Slimhole OL-KR QL40 GR OL-KR Slimhole OL-KR Slimhole OL-KR57B The natural gamma comparison between two different probes was possible in OL- KR56. Level of natural gamma radiation varies typically at µr/h in veined gneiss and granitic pegmatoid. Values can be lower in lithology containing dark minerals (mafic rock or mica gneiss). Part of granitic pegmatoid and diatexitic gneiss are showing elevated levels of µr/h. In narrow veins the natural gamma level can rise up to µr/h. Numerical values are converted onto similar level with both probes. However the larger 1 x 3 crystal in QL40 GR and longer integration time make it possible to record the data on much lower random noise level. Different lithological variation and possible changes in original sedimentary mineralogy are more distinctly imaged with more precise probe. Figure 4-1 is showing some natural gamma results measured with different probes. The natural gamma radiation results from OL-KR57 were cut at depth m, as there were not reasonable results below that depth. It looks like the slimhole probe was measuring in the drilling debris in the drillhole bottom, and possibly also without moving for a while.

26 18 Figure 4-1. Natural gamma radiation measured in drillhole OL-KR56, data from section m. Natural gamma radiation results measured with Geovista s slimhole density probe are shown with blue curve and results from ALT QL40 GR survey are shown in red curve. Lithology is shown with colours: turquoise = diatexitic gneiss, blue = mica gneiss, red = granitic pegmatoid and yellow = tonaliticgranodioritic-granitic gneiss.

27 Gamma-gamma density Geovista slimhole density probe has a Cs-137 source of 10 mci (nominal). Formerly the activity of the source and the new geometry of the tool has been calibrated with site petrophysical density distribution of the site (Aaltonen et al., 2009) and comparison between previous WellMac survey, run overlapping in deep drillhole OL-KR54 (Tarvainen & Heikkinen, 2011) and later adjusted for decaying source activity by lowering the density to correspond the estimated densities. More recently this calibration has been replaced with one based on specimen and petrophysical analysis from same drillholes than measurements from ONK-PH28, and developing a time dependent calibration (Heikkinen et al., 2016). The drillholes OL-KR56, OL-KR57 and OL-KR57B were measured with the same probe and the drillhole diameter than was used in the calibration, so the calibration can be used to these result also. Difference in level between the previous calibration and the new time dependent calibration was found to be consistently 0.05 g/cm 3 at the range of definition ( g/cm 3 ). Previous calibration produced higher values than the current. Also at very low densities at washout sections the new calibration seems to give more accurate (clearly lower than before) values. Comparison of the results of density calibrations is shown in Figure 4-2 below. Counts recorded by tool are first converted to counts per second. Then natural gamma counts per second are subtracted from simultaneously recorded Short Spaced Density (SSD) counts per second values. The SSD subtracted with GR are used to compute density values, using time dependent calibration (Heikkinen et al., 2016). Calibration is valid for this probe and source in water filled drillholes with 76 mm diameter. For other probes, sources, drillhole diameter and dry hole conditions the calibration has to be considered separately. The decay of the source (Cs-137 half-life years) will reduce the count (increase apparently the density) which is taken into account in the time dependent calibration. Tool specifications differing from the formerly used WellMac system affect the results. Higher count rate of fresh source, larger crystal and shorter spacing are increasing the nominal accuracy of readings. Shorter spacing also enhances the resolution of thin layers and fractures. A part of advantages of high count rate and large crystal are lost by shorter counting time. Short spaced density data (SSD) are very similar to previous WellMac data, with higher level of detail but containing slightly more noise which may be both temporal and spatial. Long spaced density (LSD) has deeper radius of investigation, and it averages the rock mass properties more. Ratio of the densities could be also used in interval density calculations. Short spaced density includes also effect of drillhole wall coarseness, as well as highest resolution of fractures. Core drilling produces smooth wall. Dual or compensated density would enable reduction of the effect of the wall from results.

28 20 Figure 4-2. Comparison of gamma-gamma density results from drillhole OL-KR56. Results were calculated with two different calibration functions. Blue curve is representing old calibration and red shows new calibration, which is taking time dependent changes into account. Results are shown from depth interval m. Lithology is shown with colours: dark turquoise = diatexitic gneiss, blue = mica gneiss, light turquoise = veined gneiss, red = granitic pegmatoid and white = crushed. Logged fractures are shown with circles, colour indicating fracture properties: light green = filled, dark green = grain filled, red = filled slickenside, black = tight and yellow = open fracture.

29 21 There were some sections of remarkably low density (below 2.5 g/cm 3 ). These sections are not representing true density of rock mass but instead they are indicating heavily fractured or washout zones. In OL-KR56 there were three such sections at m, m and m. In OL-KR57 there were also three sections at m, m and m. There is found intense fracturing also outside these sections, but measured densities were within reasonable rock density values at these sections. The density results from OL-KR57 were cut at depth m, as there were not reasonable results below that depth. It looks like the slimhole probe was measuring in the drilling debris in the drillhole bottom, and possibly also without moving for a while. The density results computed from short spacing tool are presented in Appendices B-1, C-1 and D-1, and the range of results also briefly in Table 4-2. Table 4-2: The range of the gamma-gamma density survey below the casing. Drillhole Depth interval (m) Range (g/cm 3 ) min max min max median OL-KR OL-KR OL-KR57B Magnetic susceptibility Raw susceptibility data measured with QL40 MagSus probe were used without tool calibration. Calibration results in air and with susceptibility pad with nominal value of 199*10-5 cgs (which was converted to SI units, *10-5 SI by multiplying with 4π) were used. These calibrations were measured before actual production logging. Calibrations for different drillholes were based on following measured values and defined factors (Table 4-3): Table 4-3: Calibration measurements and coefficients defined for different drillholes. OL-KR56 OL-KR57 OL-KR57B Nominal susceptibility in air (cgs, SI) Measured susceptibility in air, χmeas Nominal susceptibility in pad, cgs 199* * *10-5 Nominal susceptibility in pad, SI * * *10-5 Measured susceptibility in pad, χmeas Coefficient C Constant A

30 22 Calibration was computed with Equation 4-4: χ1= C* χmeas + A (4-4), where χ1 = susceptibility, C = coefficient, χmeas = measured (raw) susceptibility and A = constant. Simultaneously measured temperature was used to adjust the observed temperature drift for OL-KR56. OL-KR56 temperatures C and 26 C were used to make a linear correction between *10-5 SI and -595*10-5 SI susceptibility values, respectively. Adjustment for OL-KR56 was as shown in Equation 4-5 obtained by linear fit of (χ, T): ( *10-5 SI, C) and (-595*10-5 SI, 26 C) which was collected from measurement data, a susceptibility trend according to simultaneously measured temperature: Δχ temp = D (E*T F) (4-5), where Δχ temp = temperature correction in susceptibility, T = measured temperature during susceptibility logging at measurement station, D = comparison level from where the correction was defined, E = 1.671, coefficient of correction derived using linear fitting and F = , constant derived using linear fitting. For OL-KR57 or OL-KR57B there were no temperature based adjustments, so Δχ temp equaled 0. Adjustment was added to calibrated susceptibility value according to Equation 4-6. χ2 = χ1 + Δχ temp (4-6), where χ2 = susceptibility after temperature correction. Further drift adjustments were carried out at several stages. The values were viewed together with the site petrophysical data using histogram and cumulative probability distribution. Because the density and the susceptibility are correlating in form of so called silicate density (Puranen, 1989), the level of susceptibility compared to density was checked also by crossplotting the values on susceptibility vs. density graph together with the corresponding site petrophysical value distribution. Levels were checked and adjusted accordingly to make a correspondence by using Equation 4-7: χ3 = G*( χ2 + H) + Δχ level (4-7),

31 23 where χ3 = susceptibility after adjusting the data level, G = correction coefficient based on difference between logging and petrophysical data sets, H = correction constant based on difference between logging and petrophysical data sets and Δχ level = level correction based on remaining difference between logging and petrophysical data sets. Parameters used in processing for the drillholes are presented in Table 4-4: Table 4-4: The level adjustments for susceptibility in different drillholes. G = correction coefficient, H = correction constant and Δχ level =level correction. Drillhole Adjustments G H (10-5 SI) Δχ level (10-5 SI) OL-KR OL-KR OL-KR57B Table 4-5: The drift adjustments for susceptibility in different drillholes. Drillhole Interval (m) Δχ max (10-5 SI) N Δχ drift (10-5 SI) OL-KR *10-5 SI *10-10 SI OL-KR *10-5 SI *10-10 SI OL-KR *10-5 SI *10-5 SI OL-KR57B SI *10-5 SI In all drillholes there were found remaining a drift of susceptibility values when compared to granitic pegmatoid background levels, changing with drillhole length. The drift was possibly caused by temperature variation, or a time based variation in electromagnetic probe, but it was not recognized or removed at first stage (Equations 4-5 and 4-6). The drift was removed in several depth sections in drillholes, shown in Table 4-5, as presented in Equation 4-8. Δχ drift = n * Δχ max / Nmeasurement points (4-8), where n = running number of a measurement point and N is the total number of measurement points. The results are presented in Appendices B-1, C-1 and D-1 and briefly also in Table 4-6.

32 24 Table 4-6: The range of the susceptibility survey below casing depths. In OL-KR57 the casing caused severe disturbance in susceptibility values, therefore uppermost values are excluded (the casing depth is m). In OL-KR57B there were disturbed values above 4 m, these are excluded (the casing depth is 3.89 m). Drillhole Depth interval (m) Range (10-5 SI) min max min max median OL-KR OL-KR OL-KR57B Resistivity surveys In drillhole OL-KR56 resistivity measurements were done with two different probes, Geovista s Dual Guard Focused Resistivity probe (DLL3) and Geovista s Normal Resistivity probe (QL40 ELOG IP). Drillholes OL-KR57 and OL-KR57B were measured with DLL3. Processing and results are briefly discussed in sections 4.4.1, and Focused resistivity The focused resistivity ( dual laterolog ) results were used without internal tool file (TOL), in order to bypass the linear factory calibration of resistivity. The resistivities were instead adjusted against resistance values measured with calibration box with nominal resistances of 1, 10, 100 and 1000 Ω. The recorded values were adjusted to these nominal values using a 3 rd order polynomial function for logarithm values of the resistivities. The same function was used to convert also field measurement data from drillhole. Depth matching was started with reviewing the differences between cable marking and recorded depth in Matrix logger. Geological depth matching of dual laterolog resistivity was using the previously measured Posiva Flow Log resistance profile as support. Other matching positions were fracture locations from core logging and visible in depth adjusted ABI imaging, depth adjusted susceptibility logging at magnetized and conductive positions, increased caliper positions in mechanical and ABI caliper data, and full wave sonic velocity low positions at fractures. Dual laterolog tool has high spatial resolution which indicates responses from even narrow resistive or conductive layers (fractures etc). Measurement range is wide from < 0.1 Ωm to over 60,000 Ωm. The tool does not necessarily require compensation for drillhole fluid resistivity, porosity or drillhole diameter in similar way as normal resistivity (Elog) does. Such compensation factors are reported in literature (Brambilla et al., 2013, Crain s Petrophysical Handbook, 2016). Generally, corrections are more useful when drillhole diameter is large and bedrock porosity is high. Results are readily representing nearly true, petrophysical in situ resistivity of the rock mass. Corrected normal logging (Elog) shows similar level of resistivity. Difference on the Shallow and Deep results describes the resistivity difference of drillhole water compared to bedrock groundwater. This difference can be used to define tool specific

33 25 drillhole water correction, if found necessary (Crain s Petrophysical Handbook, 2016). This ratio can be also used to deduce resistivity of bedrock groundwater when drillhole fluid resistivity is known, and further to deduce the formation factor from fluid and rock mass resistivity. The results are presented in Appendices B-1, C-1 and D-1 and briefly in Tables 4-7 and 4-8. Table 4-7: The range of deep dual laterolog resistivity below casing depths. Drillhole Depth interval (m) Range (Ωm) min max min max median OL-KR OL-KR OL-KR57B Table 4-8: The range of shallow dual laterolog resistivity below casing depths. Drillhole Depth interval (m) Range (Ωm) min max min max median OL-KR OL-KR OL-KR57B Normal resistivity and induced polarization Normal resistivity measurement was done twice, in March 2013 and in May The results from the latter were used as they were seen to have better overall quality and there was also measured natural gamma radiation simultaneously, which eased the depth matching procedure. The induced polarisation and resistivity test surveys with Geovista s ELOG probe were done similarly than they have been done previously, as the objective for the survey was to create a reference data set measured with both Geovista s ELOG and Geovista s Dual Guard (DLL3) focused resistivity probe. Deep drillholes OL-KR1 OL-KR53 have been measured with normal logging tools manufactured by different companies and drillholes starting from OL-KR54 have been measured with DLL3. This section handles survey and data processing of Geovista s ELOG probe. The normal resistivity and single point resistance data were collected simultaneously. Before the actual survey the system performance was checked using a test box provided by the manufacturer. The calibration for single point resistance and normal resistivity results was conducted using earlier results of OL-KR29 OL-KR38. Fluid resistivity and drillhole diameter based corrections were applied according to Poikonen (1983)), Dakhnov (1962) and Löfgren & Neretnieks (2002). During the site characterization programme, the resistivity measurements in Olkiluoto deep drillholes were carried out using normal array with AM lengths of 16 and 64.

34 26 These were found appropriate in characterization of fractures and fracture zones, as the probes were providing good resolution, symmetric anomalies, and controllable effect of groundwater resistivity variation in drillholes (Poikonen 1983). Drillholes OL-KR1 OL-KR53 were measured with normal resistivity probes of different generations and from different manufacturers. Normal resistivity was also measured in several ONKALO pilot holes and characterization holes, parallel with Wenner array, which was later abandoned due to insensitivity in saline drillhole water conditions. The normal resistivity data was processed, and the resistivities were adjusted to nominal resistance values measured with calibrator box. Resistances at 1, 100, 1000 and 10,000 Ω were recorded with the probe, and the measured values were adjusted to these using 2 nd order polynomial applied for logarithm of the resistances. Values were mostly within 2 % of the nominal results, except for 1 Ω resistance where errors were 15 % at highest. Geological depth matching of normal resistivity and IP was carried out using natural gamma radiation profile recorded simultaneously with resistivity logging, and comparing this data to already depth corrected natural gamma recorded together with density logging. Further control points were collected by recognizing mutual conductive positions in normal logging and already depth adjusted dual laterolog data. A separately measured, depth adjusted groundwater electrical conductivity profile was used for removal of effects of the drillhole diameter and groundwater electrical conductivity. Electrical conductivity of the groundwater was measured two weeks before Elog normal logging using Posiva Flow log probe without the flow guides. PFL was carried out and Elog logging Electrical conductivity and temperature of the groundwater were measured during downward logging using 0.1 m station interval as continuous logging. Water was allowed to settle several days before logging of fluid resistivity, and before logging of normal resistivity. Effect of drillhole diameter and groundwater electrical conductivity was removed using analytic formula and nomogram presented by Dakhnov (1962). In the nomogram, a ratio of measured apparent resistivity to groundwater resistivity was compared to the ratio of true bedrock resistivity and groundwater resistivity. Comparison can be carried out for each normal resistivity probe length with respect to the drillhole diameter. Numerical values of correction for each probe length and 76 mm drillhole diameter were picked from nomogram, and a function was fitted for apparent resistivity to drillhole fluid resistivity as presented in Palmén et al. (2005). Correction was computed using a 3 rd order polynomial for each probe length for logarithm of the apparent resistivity to fluid resistivity. Result was used to raise 10 to the indicated power, and multiplied again with fluid resistivity to obtain the bedrock resistivity. The obtained value was used as a correction factor, normalized with an inverse of the ratio of tool surface area to drillhole surface area. The effect of drillhole fluid resistivity is seen below in Figure 4-3, where the upper part of Figure shows drillhole OL-KR56 in depth section m and the lower part shows depth section m. In the upper part of the drillhole water was fresh and relatively resistive, whereas in deeper parts it was more conductive, which affected measured bedrock resistivity values.

35 27 Initially the resistivities measured with different probe lengths are at very different levels, the shortest showing lowest resistivities and the longest the highest. Also the resistivities are highly depending on the fluid resistivity. The fluid correction changed the resistivity levels on different probe lengths on essentially similar levels, which still are showing dependency on fluid resistivity. This may be related either to salinity variation of groundwater within bedrock (in pore space) or to some remaining drillhole effect. The results are shown in Appendix B-2 and the range of results is shown in Table 4-9.

36 28 Figure 4-3. Comparison of normal resistivity (ELOG) results and focused resistivity ( laterolog, DLL) results in drillhole OL-KR56 in depth sections m and m. In the upper part of the drillhole water was fresh and relatively resistive, whereas in deeper parts it was more conductive.

37 29 Regarding the resistivity and IP results, together with susceptibility, the lower part of the drillhole OL-KR56 from 680 m downwards until the end of the drillhole at 1200 m was containing much fewer conductive layers than the interval above. Also IP anomalies were only few. Resistivity levels were low due to high salinity in drillhole water and possibly also in bedrock. Some local conductive zones were also magnetic and had slightly elevated IP. According to wide normal logging anomalies these were geometrically extensive. Between m in OL-KR56 there were found several narrow conductive layers, which were slightly scattered at m and almost continuous at m. Between m the layers were slightly elevated with IP and clearly magnetized (possibly pyrrhotite bearing). Between m layers showed clearly more elevated IP and were conductive, and they were containing less magnetized layers, so rock was likely more graphite bearing. Conductivity was developing stronger towards the lower contact, being highest at m where also the IP was highest. The rock mass changed suddenly to resistive at 680 m. Below 680 m until the end of the drillhole, the resistivities were higher than they were at m, showing sporadically presence of some narrower conductive veins or fractures. Table 4-9: The range of fluid corrected normal resistivity (elog) and IP results below the casing depth in drillhole OL-KR56. Parameter (unit) Depth interval Parameter range min (m) max (m) min max median Resistivity 8 (Ωm) Resistivity 16 (Ωm) Resistivity 32 (Ωm) Resistivity 64 (Ωm) Chargeability Ma (ms) Single Point Resistance (Ω) Full Waveform Sonic In drillhole OL-KR56 full waveform sonic measurements were done with two different probes, ALT FWS50 and ALT QL40 FWSS. Full waveform sonic survey results from OL-KR56 were processed separately for both probes. Processing is described in sections and 4.5.2, respectively. The results are briefly listed in the section and compared more detailed in the section 5.2. In drillholes OL-KR57 and OL-KR57B full waveform sonic surveys were done with ALT FWS50 probe ALT FWS50 Full Waveform Sonic processing The sonic data processing has followed the outlines defined in reports by Lahti & Heikkinen (2004, 2005a, 2005b) for the FWS50 tool. The processing consisted of visual inspection of the recording and defining P and S wave velocities and tube wave energies for both channels, and their attenuations.

38 30 Raw data was read in WellCAD (ALT, 2015) and exported to SEG-2 format to be processed in ReflexW (2003). Traces were resampled to 0.1 µs and filtered with a bandpass from 3 6 khz to khz. A phase follower was applied to pick the appropriate distinct P and S wave coherently. A semiautomatic process was continued if the automatic picking failed. Convenient multiple of a half cycle (wave length time) was subtracted from the most distinct cycle time (first maximum and minimum for S and P, respectively) to make the arrival time to match as closely as possible the true first arrival. True velocity was computed using stand-off correction (Lahti & Heikkinen 2005a, ALT 2015). The correct level of velocity was checked against the distribution of petrophysical velocity values from the site (Aaltonen et al., 2009). The data processing included the computation of P and S wave attenuations, reflected tubewave energies and finally the attenuation of tubewaves. Also dynamic rock mechanical parameters, Young s modulus Edyn, Shear modulus µdyn, Poisson s ratio νdyn, Bulk modulus and apparent Q value (Barton, 2002) were computed from the acoustic and density data ALT QL40 FWSS Full Waveform Sonic processing The four channel data was processed with semblance analysis (Paillet & Cheng, 1991) to interpret the P and S wave velocities independently without a priori data. Raw data was imported to WellCAD, bad traces were interpolated. Data was spliced to shorter than 300 m intervals to enable computer intensive processing and file transfer. The data from different channels were exported to SEG-2 files. Data was read into ReflexW software. Data points were interpolated in even 0.02 m intervals ensuring the line length will preserve and number of traces would be exactly the same in all profiles. The DC level was subtracted. Data time was cut to length of 1 ms. Due to sparse initial 4 µs time sampling in traces, the resolution of velocities was poor in high velocity crystalline rock and the velocity levels would be inaccurate and uncertain. Traces were resampled to 0.5 µs time sampling. Then the data from different channels was imported back to WellCAD. Sampling interval is adequately dense to allow high numerical accuracy and proper stacking of energy. The original sample amount 15 of summarizing window (7.5 µs) is too short with higher sampling rate, to cover the energy and wavelength of wave arrival. Modifying the length was tested, and a 120 samples window (60 µs) was found to provide adequately high amplitude in semblance analysis. The total time stacking window width was also modified from 50 µs to 100 µs in order to increase the amplitude and sharpen the computed semblance value. As an intermediary step the data was saved in ASCII format from ReflexW before importing to ensure the depths were not interpolated. Semblance interpretation computes correlation between the amplitudes from different channels over all possible velocity slopes or time delays between receiver channels. Semblance value is a ratio of summarized or stacked amplitude, normalized by original amplitude (ALT, 2015). Stacking was using 120 samples around the estimated time value at each slope value, and along 100 µs long time span which is covering delays caused by wide range of drillhole diameter values (standard settings are 15 samples and 50 µs). Using four channels and 2000 samples at 2000 µs time interval, the computing produces 3803 samples at 0.42 µs/m slowness interval from 0 to 1586 µs/m. This

39 31 interval provides 13 m/s numerical resolution for P wave velocity and 4 m/s resolution for S wave velocity. True detection accuracy is in order of m/s for P wave and m/s for S wave velocities, which is not as good as numerical resolution because of interfering reflections, related erratic skipping of cycles and small scale variation in amplitude. Resultant time represents the arrival time of specific wave form, and high amplitude values represent the times where the waveforms occur. First arrival is P wave at µs, then S wave at µs. After S wave there are one or more slower wave fronts of varying velocity, and finally will arrive several Stoneley arrivals, which have fairly constant velocity, after 700 µs time. After calculating the velocities the time profile with maximum amplitude was picked. Using velocity analysis image together with slowness profile, more precise slowness values were defined using extremum adjustment function in WellCAD velocity analysis tool. In practice, a new well log was created with a closely matching slowness (arrival time) sampled at 0.02 m interval. This was unnecessary to edit to great accuracy, as the software was detecting the time of highest amplitude from semblance log. Clear differences from the location of maximum amplitude in image were edited manually to allow better automated picking of arrival time. Finally an extremum adjustment to maximum was calculated to recognize the arrival time for each trace. Inverse of obtained slowness profile was used in computing the velocity. Semblance analysis is fairly computer intensive, and it is requiring some preparation, whereas traditional picking and stand-off correction involve more preparation and pre-processing. Time consumption of both of the methods are pretty similar. It is likely that four-channel probe with semblance analysis will provide more accurate velocity results without a priori information from velocities, and independent of knowledge on fluid velocity, though the results are not exactly identical Full waveform sonic results In drillhole OL-KR56 there was a heavily fractured depth section, which was stabilized prior to geophysical logging took place. This section ( m in core logging, marked as core loss) showed abnormal values for various parameters in full waveform sonic surveys, especially for QL40 FWSS results. These results are not, included in the statistics presented in Tables 4-10 and 4-11, as they do not represent bedrock values. Similarly, at the uppermost part (approximately 0 8 m) of OL-KR57B low P wave amplitude combined with encountered noise caused poor detection of P wave arrival and erroneous level of computed results. Therefore statistics in Table 4-13 are presented for the 8.00 m end of hole interval. All acoustic data and derived parameters are displayed in Appendices B-3 B-9, C-2, C-3, D-2 and D-3, briefly also in Tables 4-10 (OL-KR56, FWS50), 4-11 (OL-KR56, QL40 FWSS), 4-12 (OL-KR57, FWS50) and 4-13 (OL-KR57B, FWS50).

40 32 Table 4-10: The range of the full waveform sonic survey below the casing depth in drillhole OL-KR56, with ALT FWS50. Section marked as core loss ( m) was not included when calculating the statistics. Drillhole: Depth interval (m) Range OL-KR56 min max min max median Velocity P 0.6 m (m/s) Velocity P 1.0 m (m/s) Velocity S 0.6 m (m/s) Velocity S 1.0 m (m/s) Attenuation P (db/m) Attenuation S (db/m) Tubewave amplitude 0.6 m (µv) Tubewave amplitude 1.0 m (µv) Tubewave attenuation (db/m) Poisson s Ratio Shear Modulus (GPa) Young s Modulus (GPa) Bulk Modulus (GPa) Bulk Comp 1/MPa Apparent Q Table 4-11: The range of the full waveform sonic survey below the casing depth in drillhole OL-KR56 with ALT QL40 FWSS. Section marked as core loss ( m) was not included when calculating the statistics. Drillhole: Depth interval (m) Range OL-KR56 min max min max median Velocity P semblance (m/s) Velocity S semblance (m/s) Attenuation P (db/m) Attenuation S (db/m) Tubewave amplitude 0.6 m (µv) Tubewave amplitude 1.0 m (µv) Tubewave attenuation (db/m) Poisson s Ratio* Shear Modulus (GPa) Young s Modulus (GPa)* Bulk Modulus (GPa)* Bulk Comp 1/MPa* Apparent Q

41 33 Table 4-12: The range of the full waveform sonic survey below the casing depth in drillhole OL-KR57, with ALT FWS50. Drillhole: Depth interval (m) Range OL-KR57 min max min max median Velocity P 0.6 m (m/s) Velocity P 1.0 m (m/s) Velocity S 0.6 m (m/s) Velocity S 1.0 m (m/s) Attenuation P (db/m) Attenuation S (db/m) Tubewave amplitude 0.6 m (µv) Tubewave amplitude 1.0 m (µv) Tubewave attenuation (db/m) Poisson s Ratio Shear Modulus (GPa) Young s Modulus (GPa) Bulk Modulus (GPa) Bulk Comp 1/MPa Apparent Q Table 4-13: The range of the full waveform sonic results below casing depth in drillhole OL-KR57B, with ALT FWS50. At the uppermost part of OL-KR57B low P wave amplitude combined with encountered noise caused poor detection of P wave arrival, and erroneous level of computed results. Therefore statistics here are presented for the 8.00 m end of hole interval. Drillhole: Depth interval (m) Range OL-KR57B min max min max median Velocity P 0.6 m (m/s) Velocity P 1.0 m (m/s) Velocity S 0.6 m (m/s) Velocity S 1.0 m (m/s) Attenuation P (db/m) Attenuation S (db/m) Tubewave amplitude 0.6 m (µv) Tubewave amplitude 1.0 m (µv) Tubewave attenuation (db/m) Poisson s Ratio Shear Modulus (GPa) Young s Modulus (GPa) Bulk Modulus (GPa) Bulk Comp 1/MPa Apparent Q

42 Optical drillhole image The applied survey parameters of optical drillhole imaging were determined according to earlier optical televiewer works at the Olkiluoto site (Lahti 2004a, Lahti 2004b). The data processing carried out after the field work consists of the depth adjustment and the image orientation of the raw image. Field work was run downwards to avoid cloudy water conditions. Depth matching was enabled by stopping probe at each end of file recording, and running back for minimum 0.5 m of overlapping image between each section. The methods are presented by Lahti (2004a). Methods have been developed further during recent surveys in Olkiluoto (Heikkinen et al. 2016). For some reason the data in OL-KR57B had disturbed during measuring. The recording had stopped and continued to the same data file, which caused the end part of the file to become slipped upside-down. This was discovered during depth matching process, and then it was corrected. Correction process was as follows: 1. Data logs were cut apart with trial and error. This was done by importing logs partially and searching for longest possible image log run correlating with geological logging data used as reference. 2. Depth matching and other processing for both sections were done separately. There was left a short section between logs with missing data. Logs were neither merged nor interpolated, so there is a blank stripe at depth m. The images were produced to depth matched and oriented to high side presentations including a 3D image. Images were first oriented to high side with filtering recorded tool rotation around its longitudinal axis, then taking into account the tool marker position, and finally performing the computing with defined profile. Depth matching consisted of constant shift upwards or downwards of images in order to get separate survey files to a continuous depth, defining and checking of geological match points like contacts and fractures, which were checked parallel with acoustic drillhole image, defining of simple depth correction line, and computing the depth correction. Images can be viewed using WellCAD Reader or WellCAD software. For the report, images was also printed on PDF documents in scale 1:4. The optical imaging data is presented in Appendices B-10, C-5 and D-5. The depth interval of imaging survey in each drillhole is shown in Table Table 4-14: Depth interval of optical drillhole imaging below casing depths. (*) In OL- KR57B casing depth in POTTI database is 3.95 m, but according to fracture logging and this study, it s 3.89 m. Drillhole Depth interval (m) Notes of data min max OL-KR Measured in 22 pieces, each of them from top to down. OL-KR Measured in 7 pieces, each of them from top to down. OL-KR57B 3.89* Measured in 2 pieces, both from top to down. Missing data between m.

43 Acoustic drillhole image Acoustic imaging was done twice in OL-KR56. Both data sets were processed and delivered to POTTI database. Measurements are differentiated with RUN1 and RUN2 in file names. In OL-KR57 and OL-KR57B there were no re-measurements carried out. The applied survey parameters of drillhole imaging were determined according to working report (Tiensuu & Heikkinen, 2009) and modified according to Heikkinen et al. (2016). The data processing of the drillholes included depth matching and image correction. The quality of the data was controlled during the survey. The survey was never left unsupervised. The overlapping of data between recorded intervals was to be ensured by stopping the probe at end of recording of each file, running back for overlapping section and rerunning of the last 0.5 m of each recording. However, for some reason in OL-KR57B overlapping section was not measured, so there is a short section with no data at the depth m. In OL- KR56 and OL-KR57B measuring had been started while the probe was still inside the casing, in OL-KR57 data starts 5 cm below the end of casing. Image orientation and depth matching was done similarly than with optical drillhole image data as described above in section 4.6. Travel time images were first centralised with limiting time sampling interval to reasonable microseconds to avoid spurious offset centralisation at fracture locations. Then the nominal diameter of NQ3 drillbit (75.7 mm) was used to compute a densely sampled (5 m interval) profile of apparent fluid velocity, using average of tool time window recording (often 70.1 µs), tool radius 16 mm, and teaching values of drillhole radius given in automated script. Fluid velocity results were filtered with weighted average before application. After defining the apparent fluid velocity, drillhole caliper values were computed, separately minimum, maximum and average values, and image of drillhole radius. The results are presented as amplitude variation and centralised travel time images as well as variation (profiles) in the drillhole caliper (minimum, maximum and average). The caliper is also visualized in image log showing drillhole radius values according to rotation angle (azimuth), which can be further plotted to cross sections at depth values or depth intervals. The amplitude image is also presented as exaggerated 3-D view, using non-centralised travel time or radius image as caliper data. Images can be viewed using WellCAD Reader or WellCAD software. For the report, images was also printed on PDF documents in scale 1:4. The acoustic image logging results from OL-KR56 were displaying a part of the first observations of rock mechanic breakout on the drillhole wall in Olkiluoto. Breakout can be seen on amplitude images as symmetrically placed, narrow but continuous vertical stripes. Amplitude is depending on acoustic impedance contrast between drillhole fluid and rock mass. Low amplitude is indicating increased weakness in the wall. In some cases also travel time is indicating limited changes on the wall, either indicating small particles of rock material having collapsed inside into the drillhole, or particles missing from the wall (fallen off). Theoretically the breakouts are located in the direction of minimum horizontal stress component. Marks on the wall are typically only some tenths of millimeters deep, but can reach depths of more than a millimeter. (Deltombe & Schepers 2000, Ask & Ask 2007, 2017)

44 36 The mapped breakouts in OL-KR56 were observed already in the data from the first run, starting from drillhole length of m. Between m breakouts are in patches. Most of the occurrences are not continuous and present different types of breakouts (dotted, zipper-like) (Haapalehto, 2017). The length of these intervals was not increasing according to visual examination. Features are seen as parallel stripes in the amplitude images (dark vertical bands) and as elongated vertical irregularities of shape of the drillhole wall in caliper (radius) images, both expanding the radius and decreasing it (pinching or caving in). Comparing the breakout features between the runs in 2013 and 2014, very limited changes are seen in averaged lengths. Caliper maximum may have increased slightly. Caliper average is almost unaltered. Caliper minimum may have increased slightly, showing there are few locations where rock material may have caved inside into the drillhole. In ordinary fractures this is not very common. Viewing averaged cross-section logs, changes are minor. Viewing shorter intervals and all depth slices, some minor local changes may have occurred. In this case major occurrences have appeared soon after drilling. An example of comparisons between logging runs is shown in Figures 4-4 and 4-5, amplitude changes in Figure 4-4 and caliper changes in Figure 4-5. Caliper data calculated from the acoustic televiewer data and mechanical probe data were compared, results are reviewed in section 5.3 in more detail. ABI results are presented in Appendices B-11, C-6 and D-6, and caliper data also briefly in Table Table 4-15: The range of average caliper results from acoustic drillhole imaging below the casing depths. (*) In OL-KR57 the measurement had started below the casing, so that the end of casing is not visible in acoustic image. (**) In OL-KR57B casing depth in POTTI database is 3.95 m, but according to fracture logging and this study, casing depth should be 3.89 m. Drillhole OL-KR56 (2013) OL-KR56 (2014) Caliper average Depth interval (m) values (ABI) min max min max median Notes of data Measured in 11 pieces, each of them from top to down. 10 th section ended up to probe stopping into a fractured drillhole wall. Started the last section from 1120 m downwards with spring centralisers, above there were rigid centralisers Measured in 8 pieces OL-KR * OL-KR57B 3.90** Measured in 2 pieces, both from top to down. Data starts below the end of casing. Measured in 2 pieces, both from top to down. There is a gap between data files, data from m is missing.

45 37 Figure 4-4. Comparison of amplitude values in OL-KR56 between logging runs 1 and 2 in 2012 and 2014 and exaggerated cross sections showing the drillhole shape changes. Breakout features are seen as longitudinal marks on opposite sides of drillhole wall. In cross sections blue average radius is from RUN1 and red from RUN2. Minor average changes were observed at this interval.

46 38 Figure 4-5. Comparison of caliper values in OL-KR56 between logging runs 1 and 2 in 2012 and 2014 and exaggerated cross sections showing the drillhole shape changes. Breakout features are seen as longitudinal marks on opposite sides of drillhole wall. Maximum and minimum caliper values between RUN1 and RUN2 show slightly more variation at individual depths than the average over sections.

47 Caliper Two different methods of defining drillhole caliper were executed in drillholes OL- KR56, OL-KR57 and OL-KR57B. Previously caliper measurements had been performed with a mechanical caliper probe with an arm opening in fractures or otherwise open space (cavities, flushed sections). In this work it was tested also to define caliper with acoustic televiewer data, and then compared the results of these methods. The results of acoustic televiewer caliper are discussed above in Section 4.7. The comparison is discussed in Section Mechanical caliper measurements Mechanical caliper measurements were performed with a 3-arm caliper probe by Mount Sopris Instrument. The calibration was done with a set of tubes with known inner diameter. The diameter has been measured both before and after logging to compensate wearing in the hard metal tips of arms, and possible changes in level. Also the position of the arm and the optical reader indicating its relative angle may change at locations of open fractures. These changes need to be considered in processing and the base level has to be defined when processing data. Arms seem to open gradually after startup at the bottom of the drillhole. In OL-KR56 this feature was compensated by adjusting caliper level between 1030 m and end of the drillhole with adjustments of mm, in total 1.1 mm. Rest of the drillhole was left untouched, though there occur evidence that mechanic caliper level can temporarily change at open fracture locations towards larger or smaller caliper. Measurement was performed with a single arm connected, which provides highest accuracy in locating the features. The accuracy of caliper reading is 0.04 mm. Range of relevant readings is mm for a single short arm in a 75.7 mm drillhole. Small, positive or negative values are errors in reading or data communication (any values below 74 mm are considered erroneous). In OL-KR56 the uppermost measurement section m failed and data is not stored, so only the caliper derived from acoustic televiewer is available from that depth interval. The results are presented in Appendices B-1, C-1 and D-1 and the range is also shown briefly in Table Table 4-16: The range of 3-arm caliper measurements below casing depths. (*) In OL- KR57B casing depth in POTTI database is 3.95 m, but according to fracture logging and this study, casing depth should be 3.89 m. Drillhole Depth interval (m) Caliper (mm) min max min max median OL-KR OL-KR OL-KR57B 3.89*

48 Fluid resistivity and temperature The fluid temperature measurements have been calibrated using Pt-1000 electronic thermometer over the range measurable in Olkiluoto drillholes, 5 20 C. The accuracy of the temperature recording is 0.01 C. Since the tool response of resistivity is linear only for very resistive fluids, a non-linear (2 nd order) calibration function was deduced. The fluid resistivity was calibrated using solutions of known NaCl concentration and electrical conductivity (EC) from literature (Eutech Instruments, 2016) for temperature of 25 C, and measuring raw data from the solutions with Mount Sopris PFA fluid resistivity probe at measurement temperature. Presented dependency of weight percentages and conductivity was converted to resistivity, and extrapolated between given the values (0.1 g/l, 0.3 g/l 100 g/l) to match concentrations of prepared solutions (Eutech Instruments, 2016). Literature values were used due to the strong frequency dependence of EC measurements, therefore requiring increasingly high frequencies to avoid saturation with increasing ion concentration (Radiometer Analytical, 2004). The theoretical EC values in 25 C were converted to measurement temperature T C of the NaCl solution samples using conversion relation (Equation 4-10) presented in Poikonen (1983). ρ25 C = ρt C * ( *T) (4-10), where ρ25 C = fluid resistivity corrected to 25 C ρ T C = fluid resistivity in measurement temperature T = measured temperature The calibration measurements with NaCl fluids from 2004 (Lahti & Heikkinen, 2005b) are listed in Table A function was fit on logarithmic scale between these observation values, and further applied to compute resistivities from pulse values. Table 4-17: Calibration measurements with NaCl (Lahti & Heikkinen 2005b). NaCl solutions, concentrations (g/l) Results Resistivity in 25 C (Eutech Instruments, 2016) Resistivity in T C (Poikonen, 1983) Measured pulses in T C (Mount Sopris PFA)

49 41 A function was deduced to convert the obtained data in pulses (range ) to actual fluid resistivity values. The data values were then converted both to resistivity in temperature 25 C, and to apparent Total Dissolved Solids (TDS, g/l) values according to Heikkonen et al. (2002). Measurement is rather insensitive at high salinity values g/l ( Ωm), where also electromagnetic noise of the site has a large influence. Noise can be caused by small particles present in the fluid, too. Reading accuracy of fluid resistivity recording is Ωm at the whole measurement range 0.05 approximately 200 Ωm). The measured fluid resistivity in OL-KR56 is at 7 8 Ωm at depth interval between m, and is then lowering to level of 3 5 Ωm to the rest of drillhole length. This is indicating the open drillhole conditions. As a separate measurement, a drillhole fluid resistivity measurement using Posiva Flow Log (PFL) equipment was carried out two weeks before Elog measurements ( ). This measurement was run without pumping in the drillhole, upper flow guides connected, with a constant logging speed rate of 1 m/min. Tool resistivity reading is well calibrated and documented in survey memorandums delivered to Posiva. Compared to readings of Mount Sopris probe, the values at the top of hole are at similar 5 6 Ωm level, lowering suddenly at 80 m to 1.7 Ωm and at 130 m to 1.2 Ωm. Values are lowering between m gradually from 1 Ωm to 0.2 Ωm, and finally at the end of the hole below 0.1 Ωm. Mount Sopris probe was found to be malfunctioning soon after this survey campaign, but the data from this survey campaign seems reliable. The fluid resistivity and temperature results from OL-KR57 were cut at depth m, as there were not reasonable results below that depth. It looks like the probe was measuring in the drilling debris in the drillhole bottom, results representing that mud instead of drillhole fluid. The results are presented in Appendices B-12, C-4 and D-4. The range of measurements is shown briefly in Tables 4-18, 4-19 and Table 4-18: The range of fluid resistivity and temperature measurements in drillhole OL-KR56. Please note that the measurements have started above the casing depth m. Parameter (unit) Survey depth (m) Values min max min max Fluid temperature T ( C) Fluid resistivity, true T (Ωm) Fluid resistivity, 25 C (Ωm) Total Dissolved Solids (g/l)

50 42 Table 4-19: The range of fluid resistivity and temperature measurements in drillhole OL-KR57. Please note that the measurements have started above the casing depth m. Parameter (unit) Survey depth (m) Values min max min max Fluid temperature T ( C) Fluid resistivity, true T (Ωm) Fluid resistivity, 25 C (Ωm) Total Dissolved Solids (g/l) Table 4-20: The range of fluid resistivity and temperature measurements in drillhole OL-KR57B. Please note that the measurements have started above the casing depth (3.89 m or 3.95 m). Parameter (unit) Survey depth (m) Values min max min max Fluid temperature T ( C) Fluid resistivity, true T (Ωm) Fluid resistivity, 25 C (Ωm) Total Dissolved Solids (g/l)

51 43 5 COMPARISON OF EQUIPMENT AND DATA IN OL-KR56 During this survey programme some test and comparison measurements were done in drillhole OL-KR56. Differences in hardware, operation and processing are discussed mostly in previous sections, but in this section we have some comparison between different probes regarding resistivity, full waveform sonic and, acoustic imaging and caliper. 5.1 Resistivity measurements Purpose for resistivity re-measurement was to provide less disturbed data than what was achieved in the first run, and to provide comparison data for Normal Resistivity array which was used consistently in almost all deep drillholes OL-KR1 OL-KR53 in and for Laterolog array used in OL-KR54 OL-KR56 and in several ONKALO pilot holes starting from ONK-PH12 and ONK-KR13. Initially electrical logging in pilot holes was carried out with Wenner probe (Rautaruukki Oy, 30 cm), later together with Geovista Elog Normal, until Wenner was abandoned due to quality problems in saline water and larger diameter drillholes. In pilot holes normal array was replaced with Dual Laterolog probe after testing it in 2010 in characterization hole ONK-KR13, where an overlapping section of 100 m with DLL and ELOG was produced. Unfortunately ELOG probe was lost to another site soon after that and further comparison was not possible. That 100 m section in granitic pegmatoid and at fairly low resistivity was inadequate for a more comprehensive comparison. Another comparison was made in ONK-PH19, where Smoy demonstrated ALT ELOG IP and resistivity probe in 2012, measuring both resistivity and IP. Also this 100 m section is fairly short for a comprehensive analysis. Data was not processed further, but proofing similarities and differences between survey with two probes on a longer section covering large variation in drillhole water salinity (electrical conductivity) and different lithological units, as well as fracturing, was considered useful. Fluid resistivity and drillhole diameter corrections were enabled by running drillhole water resistivity survey with Posiva Flow Log near the timing of Elog Normal logging (with two weeks difference in time). During later stage of the campaign, there emerged an opportunity to test and take into production a focused dual laterolog probe, which SKB was reporting to have interesting properties with respect to resolution and fracture detectability (Löfgren & Neretnieks, 2002). The laterolog probe was tested in ONK-KR13 (Tarvainen, 2011) and taken into production measurements in ONK-PH12 (Lahti et al., 2011) onwards in ONKALO, and in OL-KR53 OL- KR57 (Tarvainen 2010, Tarvainen & Heikkinen 2011). There was no comprehensive overlapping measurement in long drillhole (with an exception of ONK-KR13 and ONK-PH19, 100 m each), so it was decided to provide a consistent measurement with both arrays from OL-KR56, using state of the art processing for normal resistivity logging.

52 Focused Resistivity The dual laterolog probe can be used to measure location of fractures and conductive layers with high precision and obtaining fairly correct levels of resistivity, despite of conductive groundwater filling in drillholes. Effects of drillhole fluid are associated with large drillhole diameter and high porosity which are not present at Olkiluoto, and partially with decentralization of probe, and high resistivity contrast between drillhole fluid and bedrock, which are encountered in Olkiluoto bedrock, especially deeper (Crain s Petrophysical Handbook, 2016). Levels of both resistive and conductive layers are reproduced in fairly reliable way. Lowest resistivities in casing were 3 4 Ωm with laterolog probe, which is clearly offset from true steel values. This offset data is due to the resistivity probe data s tendency to saturate at high conductivities, depending on for example conductive environment or probe geometry. Conductive layers in bedrock receive possibly more realistic resistivities from 1 10 Ωm with dual laterolog than with normal array logging. Minimum thickness of a conductive layer imaged in logging is in order of 20 cm, dictated by the voltage electrode pair spacing. True thicknesses can be in order of parts of millimeters. Location and length of bridle is seen at some wider conductive layers as decreasing trend towards the lower contact of the electrically conductive layer. Also even narrow (20 cm) resistive layers are correctly imaged with their resistivities. High resistivities are seen higher in laterolog data than in normal logging. Wide intervals with even and high resistivity are shown in similar manner and at same resistivity levels both with laterolog and fluid corrected normal logging. Laterolog is much more sensitive in detection of narrow conductive zones like water filled fractures. Also the anomalies caused by fractures are much sharper and deeper. Small fractures and conductive layers are undetected in normal logging, especially in presence of conductive drillhole water, which is smoothing out anomalies. Effect of drillhole diameter and conductive water filling are considered small in laterolog results, though correction factors are published. Difference of the shallow and deep resistivity in dual laterolog is related to difference of electrical conductivity of the water in drillhole and in the bedrock (filling in porous space) ELOG IP Normal Resistivity The normal resistivity and IP probe is designed to provide comparably reliable resistivity levels from conductive layers which are thicker than the tool length (spacing AM). Different electrode spacing from 8 to 64 can be used to separate layer thicknesses, and to assess the extent of conductive layers from the drillhole. Smallest fractures and other small conductors are visible only in the shortest electrode lengths. Tool can be used also in assessment of drilling mud penetration in sedimentary rock types. The resistivity of resistive layers is more dependable on drillhole fluid resistivity, but resistivity levels of wide resistive layers can be estimated after fluid correction. Normal logging produces dual spikes in conductive layers, which is widening the anomalies. In addition to this it also complicates profiles in cases where several conductive layers are located near each other.

53 45 Normal resistivity probes have slightly narrower full range of resistivity than dual laterolog, for example so that lowest measurable resistivities in OL-KR56 with normal array probe s 64 electrode spacing were some Ωm, with 32 some Ωm, and with 16 some Ωm. These were depending much on fluid resistivity. Narrow conductive layers were better detected with 8 electrode spacing. Wider layers had lowest resistivities at Ωm. Higher fluid resistivities were narrowing down the range. Lowest resistivities with normal probe were Ωm in casing (steel), which was not true steel resistivity due to the saturation of the probe. Saturation of upper resistivities did not emerge in OL-KR56. Highest measured resistivities were 30,000 Ωm. In some cases with fresh (non-conductive) groundwater in drillhole the high resistivities may saturate at 50, ,000 Ωm, saturation level depending on probe, electrode distance and environmental conductivity, and sensitivity of the probe. Generally the DLL probe has higher sensitivity and range, and normal probe will exceed the measurement limits (or saturate) earlier, at lower resistivities Comparison of resistivity measurements Comparing the logging data from the two probes indicates that after correcting the effects of drillhole diameter and fluid properties, the normal resistivity and focused resistivity data values are very similar at resistive intervals in the bedrock. The four different AM distances of normal resistivity assist in evaluating the extent of conductive horizons, like fractures, fracture zones and veins containing conductive minerals. Different resistivity measurements and magnetic susceptibility are shown in Figures 5-1 and 5-2 together with lithological and natural gamma radiation and density data. Fluid corrected (Dakhnov, 1962) normal resistivity is representing almost identical results at different electrode spacing values, though 8" and 16" show highest resolution at narrow layers. Non-corrected values differ significantly due to influence of drillhole diameter and salinity of water. Corrected values at resistive intervals are 25,000 30,000 Ωm at the top and 2,000 Ωm at the bottom, where non-corrected range is between 5,000 25,000 Ωm at top of the drillhole, and 200 1,500 Ωm at the bottom of the drillhole. Normal resistivity is corrected with the fluid and diameter correction to adequate level. These are shown in Figure 4-3. Dual laterolog profiles are non-corrected, and show identical 30,000 Ωm levels as normal resistivity, but are much more detailed. Shallow and deep curves are similar at the top of the drillhole.

54 46 Figure 5-1: Different anomaly pattern in dual laterolog (black curve) and normal resistivity data (orange, red, green and blue curves), overview in large scale.

55 47 Figure 5-2: Different anomaly pattern in dual laterolog (black curve) and normal resistivity data (orange, red, green and blue curves), detailed view. Details retain also deeper, but the level of resistivity is lowering significantly to 200 1,500 Ωm, and the shallow and deep resistivity values start differing from 500 m downwards, where the resistivity of water is also decreasing strongly. This is likely to be caused by both saline water in the bedrock, dropping the resistivity levels in both normal and focused resistivity, and by saline water in drillhole which start to suggest need for compensation below 500 m. In ONKALO pilot holes the water is usually refilled by fresh surface water, which means that the compensation may there not be strictly necessary, and the need can be assessed by difference between shallow and deep resistivity profiles. Normal resistivity with induced polarization measurement is a useful support for mineralogical and deformation characterization, as together with resistivity and susceptibility logging it can help in separating the magnetized or non-magnetized, conductive, and disseminated mineralogy associations. However, only larger conductive bodies are well detected, especially at highly conductive drillhole water intervals, and the anomalies tend to be smooth and wide. On the contrary, as the large scale features and resistive intervals are fairly similar in normal and focused resistivities, the details in conductive layers are much more prominent in focusing tool. Even smaller conductive

56 48 features like water bearing fractures cause distinct, well localised anomalies, where the resistivity level is closer to realistic than with normal logging in these conditions. Detectability and resolution of normal resistivity logging is better with single point resistance measured with normal logging, and in same order as with Posiva Flow Log SPR, with the difference that the resistivity level is calibrated. In this basis it can be stated that normal logging has been useful in site characterization, but can be replaced reliably with a focused probe, which is providing similar but more detailed results from the bedrock. Accuracy is helping for example in characterization of hydraulically conductive fractures. 5.2 Comparison of full wave form sonic measurements ALT FWS50 Two-channel data contains severe interference at early times between 35 and 85 m. Interference was caused either by a damaged probe or by logger unit. Elsewhere the data quality is good. P wave arrival is seen in first receiver channel at 140 µs and in second channel at 210 µs. The P arrival is weak. Stronger S arrivals are found at 250 µs in first channel and at microseconds in second channel. The S arrivals are mixed by late P wave multiples and in some places also by reflected tubewaves at fracture locations. Arrival times are varying strongly according to lithology and are also delayed at fractures and larger fracture zones. Amplitude of both P and S wave arrivals are varying also according to lithology and fracturing. Many fractures cause upward and downward going tubewave reflections, which can be seen as hyperbolic patterns centered at the fracture location. Direct tubewave arrivals are seen from 450 µs onwards at first channel and at 700 µs at second channel. Amplitude of tubewave is varying according to location ALT QL40 FWSS Recorded full wave sonic images of four-channel probe ALT QL40 FWSS are pretty similar to the ones measured with two-channel probe. P and S wave arrivals are stronger than with two-channel probe. The measurement produces three different full waveform sonic images. Wideband image is similar as with two-channel probe, and it can be used in interpretation of acoustic velocities and picking of P and S wave amplitudes. Chevron image is displaying low frequency reflected waves generated in open fractures. The name chevron refers to the symmetric v-shaped form of these reflections. Tubewave image is showing at high frequencies the reflections and energy of tubewaves. The image can be used in computing the tubewave energy and attenuation. Two-way reflections can be obtained from m distance. In four-channel probe ALT QL40 FWSS the computed S wave is pretty clear in most cases. There are some cases, like occurrence of early time noise, causing the computed semblance to show higher non-coherent amplitudes overlapping with P wave indication. Overcoming this error required some testing, like extending the time window or sample spacing, or muting the first µs from each trace before processing. Computed semblance analysis is noisy and partially masking the P wave information between 40

57 m. Below 180 m the P wave is weaker than S wave but distinct. S wave is fairly well defined at the whole measured depth range Comparison The P and S wave velocities between the manually picked two-channel probe FWS50 data and the semblance processed four-channel QL40 FWSS data in OL-KR56 were compared. Also rock mechanic properties were computed from data of both probes. An example of comparisons is shown below in Figure 5-3. Figure 5-3. Comparison of full waveform sonic survey results in drillhole OL-KR56. Logs marked with 2 Ch show data measured with ALT FWS50 probe, which has one transmitter and two receivers. Logs named with 4 Ch or semblance show results from ALT QL40 FWSS probe measurement. Length resolution of the short 0.6 m transmitter receiver separation in FWS50 is equally good as in the semblance processed profile from QL40 FWSS. The same velocity variation is visible in both profiles. The semblance processed velocity values are slightly lower compared to the manually picked and estimated velocity levels and vary according to depth interval. The P wave velocity median in manually picked

58 50 FWS50 profile at m depth level was 5830 m/s and in QL40 FWSS semblance analysis 5593 m/s, with difference of 4.2 %. The S wave velocity median in manually picked profile was 3344 m/s and in semblance analysis 3262 m/s, with difference of 2.5 %. The P to S wave ratio is 1.74 (FWS50) or (QL40 FWSS), the difference being 1.7 %. Standard deviations are quite similar, for P wave in manual picking 315 m/s and semblance 256 m/s, and for S wave in manual picking 156 m/s and in semblance 178 m/s. Both P and S wave median velocities would be higher if taking into account the whole measured drillhole interval down to length of 1180 m, because velocities are increasing with depth. The S wave velocity was clearly higher (> m/s) in manually picked profile (FWS50) at m and m, and elsewhere closer to velocity defined by semblance analysis (QL40 FWSS). Similar 200 m/s difference was found for P wave velocity at m and at m. This difference in P velocity levels is seen above in Figure 5-3. Numeric accuracy of velocity determination (arrival time accuracy) is in order of m/s depending on wave form. Random noise level was assessed with subtracting running average profile from measured data. It was found that in both first arrival based picking and in semblance analysis the random noise level is lower than numeric precision, and for S wave lower than for P wave. There was no great difference between the data sets, though semblance seems to be slightly more accurate. Difference between the probes and processing techniques was likely caused by the difficulty of defining the correct velocity level of single channel arrival times, and noise related to the time difference definition. The phenomenon can be caused also by variation in fluid velocity which was unknown and treated as constant in two-channel processing, not required in semblance analysis, and possibly from variation in alignment of probe in the drillhole. The semblance processed velocity profile has slightly more spurious and spikey values than the manually picked one. In some cases the velocity is deviating more between the two methods, probably due to higher averaging of semblance analysis, over m distances. Both methods can be considered equally good in velocity definition, though semblance can produce more reliable level of velocity without external a priori information or assumed velocities. Weakness in the manual arrival picking and standoff correction is the unknown acoustic velocity of fluid. 5.3 Comparison of mechanical and ABI caliper Caliper measurements are showing small scale variation in drillhole diameter, either as a single profile like with mechanical probe, or as profiles of minimum, average and maximum diameter at each drillhole length, and an image of variation of drillhole radius on circle, as with acoustic televiewer. Caliper shows locations where washout has occurred in fracture filling, showing increased opening from less than millimeter to several millimeters. The mechanical caliper with single arm connected has a maximum caliper reading of mm. In acoustic televiewer the maximum value is greater. Caliper anomalies are considered showing locations of open fractures, which have been used for detection of hydraulically conductive fractures, and avoiding drillhole sections

59 51 causing potential hazard for tool safety, for example not to damaging packers in hydraulic head monitoring, water sampling, stress measurements or thermal conductivity measurements. Figure 5-4: Mechanical and acoustic televiewer (ABI) derived caliper. Green curve is showing average caliper according to acoustic televiewer survey (RUN2) in 2014, red curve is showing caliper measured with mechanical probe. Lithology is shown with colours: dark turquoise = diatexitic gneiss, red = granitic pegmatoid, blue = mica gneiss and light turquoise = veined gneiss. Logged fractures are shown with circles, colour indicating fracture properties: light green = filled, dark green = grain filled, red = filled slickenside, black = tight and yellow = open fracture. Mechanical caliper is indicating well the locations of major open fractures and fracture zones. The result is showing also depth intervals where hardness variation in lithology or intensity of fracturing causes variation in diameter. Profile in general is fairly smooth, with little variation. In OL-KR56 the calibration defined after measurement was used, but changes were taken into the caliper level at several depth locations to move the level to higher value at mm steps. Actual level of the caliper is within mm from the true diameter, and the variation is well characterized with

60 52 smaller than 0.1 mm detection threshold. In the results some sudden changes as well as transient (ramp-like) changes after sudden ones can be seen, likely due to probe s arm sticking and gradual returning to true state afterwards. These level changes can be seen in Figure 5-4, showing an example of data from OL-KR56. It can be seen that mechanical caliper is less sensitive to small changes in caliper than acoustic televiewer. Dense sets of fractures (or remarkable open fractures) cause mechanical caliper data level changes, which tend to return to more correct level gradually. It can be seen also that in OL-KR56 data mechanical caliper is having mm bigger values than average ABI caliper and it is likely on too high level. Drillholes OL-KR57 and OL- KR57B were shorter and had fever level changes than OL-KR56. The caliper values computed from acoustic televiewer have clearly higher resolution than with the mechanical caliper. The caliper image shows positions where on the fracture trace the open cavities or channels are. Maximum caliper gives also an estimate on how large the cavities are. Small scale variation caused by lithological variation and drillbit wearing are shown in more detail even in average caliper. The same large features are seen in caliper computed from ABI than in mechanical probe, but smaller details can be detected, as well as variation within fracture zones. Based on amplitude images and caliper images, it is possible to orient fractures. The actual level of caliper is relying on assumption that most of drillhole inner diameter is at least and close to nominal diameter of drillbit or reamer (75.7 mm for NQ3). Then the nominal value is fed into computing formula to define apparent acoustic velocity in fluid, which can be in turn used to compute radius and caliper from centralized travel time. Fluid acoustic velocity is sensitive to temperature, pressure and salinity, and it is varying quite a lot along drillhole. Selections in processing, like selection and application of time window in acoustic trace detection, are also affecting to the accuracy to some extent. Time window should be as close as possible to the recorded one, though avoiding spurious changes. Resolution of diameter is better than 0.1 mm, but absolute level can have uncertainty of mm, expecting correct calculation procedure with relevant source data. Acoustic televiewer data is sensitive to disturbance caused by gas bubbles in the water since the signal does not travel in gas. In drillhole OL-KR56 there were some disturbances, possibly caused by gas. Especially maximum caliper values were suffering a lot, and average data had some problems as well. These can be filtered out to some extent as it was done to RUN2 data in OL-KR56 as shown in Figure 5-5. Measuring with acoustic televiewer is planned to be done downwards and in relatively steep drillholes, and small drillhole inclination as well as upwards survey run direction may cause problems since drillhole fluid should be able to flow freely through the logging head, and the probe should be carefully centralized in the drillhole.

61 53 Figure 5-5: Mechanical and acoustic televiewer (ABI) derived caliper. Minimum, maximum and average caliper values of acoustic televiewer surveys are shown from both RUN1 and RUN2. Violet and red curves are showing minimum caliper values from ABI runs, yellow and blue are showing maxima. Green curves are showing average caliper values according to ABI surveys, red curve in right side of the figure is showing caliper measured with mechanical probe. ABI data is filtered from spikes before calculation of caliper. Lithology is shown with colours: dark turquoise = diatexitic gneiss and red = granitic pegmatoid. Logged fractures are shown with circles, colour indicating fracture properties: light green = filled, dark green = grain filled, red = filled slickenside, black = tight and yellow = open fracture.