Flow and Electrical Conductivity Measurements During Long-Term Pumping of Drillhole OL-KR6 at Olkiluoto, Results from June 2010 Measurements

Transkriptio

1 Working Report Flow and Electrical Conductivity Measurements During Long-Term Pumping of Drillhole OL-KR6 at Olkiluoto, Results from June 2010 Measurements Janne Pekkanen March 2011 POSIVA OY Olkiluoto FI EURAJOKI, FINLAND Tel Fax

2 Working Report Flow and Electrical Conductivity Measurements During Long-Term Pumping of Drillhole OL-KR6 at Olkiluoto, Results from June 2010 Measurements Janne Pekkanen PRG-Tec Oy March 2011 Base maps: National Land Survey, permission 41/MML/11 Working Reports contain information on work in progress or pending completion. The conclusions and viewpoints presented in the report are those of author(s) and do not necessarily coincide with those of Posiva.

3 FLOW AND ELECTRICAL CONDUCTIVITY MEASUREMENTS DURING LONG-TERM PUMPING OF DRILLHOLE OL-KR6 AT OLKILUOTO, RESULTS FROM JUNE 2010 MEASUREMENTS ABSTRACT The Posiva Flow Log, Difference Flow Method (PFL DIFF) uses a flowmeter that incorporates a flow guide and can be used for relatively quick determinations of hydraulic conductivity and hydraulic head in fractures/fractured zones in cored drillholes. This report presents the principles of the method and results of measurements carried out in drillhole OL-KR6 at the Olkiluoto investigation site in June Previously reported results from measurements made between October 2007 and December 2009 are also presented for comparison, reports WR /Pekkanen, J., 2009/ and WR /Pekkanen, J., 2010/. In this study the Posiva Flow Log was used for measurements of flow and electrical conductivity of water during long-term pumping. The aim of the measurements was to detect possible changes in the electrical conductivity of fracture-specific water during the long-term pumping period. Flow rates from fractures were also measured. The measurements in drillhole OL-KR6 were carried out in the depth intervals c. 24 m 64 m, 98 m 140 m and 396 m 424 m. The flow rate into a 0.5 m long test section was measured using 0.1 m point intervals. The occurrence of saline water in the drillhole was studied by electrical conductivity measurements. The target fractures were chosen on the basis of their flow rates and they were the same as in the earlier measurements. Keywords: Groundwater, flow, measurement, bedrock, drillhole, electrical conductivity, Posiva Flow Log.

4 VIRTAUSERO- JA SÄHKÖNJOHTAVUUSMITTAUKSET PITKÄAIKAIS- PUMPPAUKSEN AIKANA KAIRAREIÄSSÄ OL-KR6, TULOKSET KESÄKUUN 2010 MITTAUKSISTA TIIVISTELMÄ Posiva Flow Log virtauseromittausmenetelmää (PFL DIFF) voidaan käyttää suhteellisen nopeaan vedenjohtavuuksien ja virtauspaineiden määrittämiseen raoista tai rakovyöhykkeistä kairanrei issä. Menetelmässä käytetään virtausanturia, johon mitattavan syvyysvälin virtaus johdetaan virtausohjaimella. Tässä raportissa esitetään mittauksen periaatteet ja tulokset mittauksista, jotka tehtiin kairanreiässä OL-KR6 Olkiluodon tutkimusalueella kesäkuussa Lisäksi vertailun vuoksi tuloksissa on esitetty edellisten raporttien tulokset 2007 lokakuun ja vuoden 2009 joulukuun väliseltä ajalta, raportit WR /Pekkanen, J., 2009/ ja WR /Pekkanen, J., 2010/. Tässä raportissa Posiva Flow Log menetelmää on käytetty virtausten ja sähkönjohtavuuden seurantaan pitkäaikaispumppauksen aikana. Raportissa esitettyjen mittausten tarkoituksena oli tarkkailla mahdollisia muutoksia veden sähkönjohtavuudessa ja virtauksissa tietyissä raoissa kairanreiän OL-KR6 pitkäaikaisen pumppauksen aikana. Kairanreiästä OL-KR6 on valittu mitattavaksi syvyysvälit n. 24 m 64 m, 98 m 120 m ja 396 m 424 m. Virtaus testisektoriin mitattiin käyttäen 0.5 m mittausväliä 0.1 m siirroin. Veden sähkönjohtavuutta (EC) mitattiin valittujen rakojen kohdalla. Raot valittiin aiempien mittausten mukaisesti, sekä raosta reikään mitatun virtauksen perusteella. Avainsanat: Pohjavesi, virtaus, mittaus, peruskallio, kairanreikä, sähkönjohtavuus, Posiva Flow Log.

5 1 TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ 1 INTRODUCTION PRINCIPLES OF OPERATION INTERPRETATION Hydraulic head Transmissivity and hydraulic head Fresh water head EQUIPMENT SPECIFICATION FIELD WORK AND RESULTS EC of drillhole water Flow measurements EC of fracture specific water CONCLUSIONS REFERENCES APPENDICES Appendix 1.1 Drillhole OL-KR6, Electrical conductivity of drillhole between time period October 2007 and June 2010 Appendix 1.2 Drillhole OL-KR6, Temperature of drillhole water between time period October 2007 and June 2010 Appendices Drillhole OL-KR6, Fracture specific electrical conductivity, flows from the fracture to the drillhole, water level and pumping rate between time period October 2007 and June 2010 Appendices Drillhole OL-KR6, Flow rate between time period October 2007 and June 2010 Appendices Drillhole OL-KR6, Electrical conductivity of drillhole water during flow measurements between time period October 2007 and June 2010 Appendices Drillhole OL-KR6, Fracture specific EC results by date, time series of June 2010 measurements Appendices Drillhole OL-KR6, Table of Fracture specific EC and flow rates, time series of June 2010 measurements Appendices Drillhole OL-KR6, Water level and pumping rate, Long-term flow rate and electrical conductivity between time period January 2004 and June 2010 Appendix 7.4 Drillhole OL-KR6, Water level and pumping rate, Long-term flow rate and electrical conductivity at fracture m between time period January 2004 and June 2010

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7 3 1 INTRODUCTION Olkiluoto in Eurajoki is the selected site for the final disposal of high-level spent nuclear fuel deep into the bedrock. The main objective of PFL DIFF (Posiva Flow Log, Difference Flow Method) measurements at Olkiluoto is to identify water-conductive sections and/or fractures that are suitable for subsequent hydro-geochemical characterization. Secondly, the measurements target hydrogeological characterization, which includes the prevailing water flow balance in the drillhole and the hydraulic properties (transmissivity and undisturbed hydraulic head) of the tested sections. The aim of the measurements in drillhole OL-KR6 at Olkiluoto was to detect possible changes in electrical conductivity and flow rates during a long-term pumping test. Drillhole OL-KR6 was selected for the test, because it had been measured several times using the PFL DIFF. It was measured for the first time in 1999 (Rouhiainen 1999) during pumped conditions, when its length was about 300 m. The drillhole was extended to the depth of about 600 m by core drilling in the year After the extension, the drillhole was re-measured in both un-pumped and pumped conditions (Pöllänen and Rouhiainen 2000). The pumping test was started on March 22, Monitoring measurements were also started in March Measurements before June 2010 have been reported earlier (Pöllänen and Rouhiainen 2002, Pekkanen et al. 2004, Pekkanen et al. 2006, Pekkanen and Pöllänen 2008, Pekkanen 2009, Pekkanen 2010). This report presents the results that were obtained in June 2010 and also compares the results to earlier measurements. The measurements were carried out at depth intervals c. 24 m 64 m, 98 m 140 m and 396 m 424 m. The flow rate into a 0.5 m long test section was measured using 0.1 m point intervals. The location of OL-KR6 at Olkiluoto is illustrated in Figure 1-1. The equipment employed in the PFL DIFF method (a trailer-mounted winch and cable, a downhole probe and a computer) can be used in drillholes of depths up to 1500 m that have a diameter of 56 mm or greater. A high-resolution absolute pressure sensor is used to measure the total pressure along the drillhole, with measurements being carried out in parallel with flow measurements. The results obtained are used in calculating the hydraulic head along the drillhole.

8 Figure 1-1. Location of drillhole OL-KR6 at the Olkiluoto site. 4

9 5 2 PRINCIPLES OF OPERATION Unlike conventional drillhole flowmeters which measure the total cumulative flow rate along a drillhole, the PFL DIFF probe measures the flow rate into or out of defined drillhole sections. The advantage that follows from measuring the flow rate in isolated sections is improved detection of incremental changes of flow along the drillhole. As these are generally very small, they can easily be missed when using conventional flowmeters. Rubber sealing disks located at the top and bottom of the probe are used to isolate the flow of water in the test section from the flow in the rest of the drillhole, see Figure 2-1. Flow inside the test section is directed through the flow sensor. Flow along the drillhole is directed around the test section by means of a bypass pipe and is discharged at either the upper or lower end of the probe. The entire structure is called the flow guide. Generally two separate measurements with two different section lengths (e.g. 2 m and 0.5 m) are used. The 2 m setup is usually used first to obtain a general picture of the flow anomalies. It is also good for measuring larger (less than 2 m in length) fractured zones. The 0.5 m section setup can separate anomalies which are close to each other. Different section lengths are also used to confirm that a flow anomaly is real and not caused for instance by a leak at the rubber disks. Flow rates into or out of the test section are monitored using thermistors, which track both the dilution (cooling) of a thermal pulse and its transfer by the moving water. The thermal dilution method is used in measuring flow rates because it is faster than the thermal pulse method, and the latter is used only to determine flow direction within a given time frame. Both methods are used simultaneously at each measurement location. In addition to incremental changes in flow, the PFL DIFF probe can also be used to measure: The electrical conductivity (EC) of both drillhole water and fracture-specific water. The electrode used in EC measurements is located at the top of the flow sensor, see Figure 2-1. The single point resistance (SPR) of the drillhole wall (grounding resistance). The electrode used for SPR measurements is located between the uppermost rubber sealing disks, see Figure 2-1, and is used for the high-resolution depth determination of fractures and geological structures. The prevailing water pressure profile in the drillhole. Located inside the watertight electronics assembly, the pressure sensor transducer is connected to the drillhole water through a tube, see Figure 2-2. The temperature of the water in the drillhole. The temperature sensor is part of the flow sensor, see Figure 2-1.

10 6 Pump Winch Computer Measured flow EC electrode Flow sensor -Temperature sensor is located in the flow sensor Single point resistance electrode Rubber sealing disks Flow Flow along along the the borehole drillhole Figure 2-1. Schematic of the probe used in the PFL DIFF. CABLE PRESSURE SENSOR (INSIDE THE ELECTRONICSTUBE) ASSEMBLY) FLOW SENSOR FLOW TO BE MEASURED RUBBER RUBBERSEALING DISKS DISKS FLOW ALONG THE DRILLHOLE BOREHOLE Figure 2-2. The absolute pressure sensor is located inside the electronics assembly and connected to the drillhole water through a tube.

11 7 The principles behind PFL DIFF flow measurements are shown in Figure 2-3. The flow sensor consists of three thermistors (Figure 2-3 a). The central thermistor, A, is used both as a heating element and to register temperature changes (Figures 2-3 b and c). The side thermistors, B1 and B2, serve as detectors of the moving thermal pulse caused by the heating of A. Flow rate is measured by monitoring heat transients after constant power heating in thermistor A. The measurement begins by constant power (P 1 ) heating. After the power is cut off the flow rate is measured by monitoring transient thermal dilution (Figure 2-3 c). If the measured flow rate exceeds a certain limit, another constant power heating (P 2 ) period is started after which the flow rate is re-measured from the following heat transient. Flows are measured when the probe is at rest. After transferring the probe to a new position, a waiting period (which can be adjusted according to the prevailing circumstances) is allowed to elapse before the heat pulse (Figure 2-3 b) is applied. The measurement period after the constant-power thermal pulse (normally 100 s each time the probe has moved a distance equal to the test section length and 10 s in every other location) can also be adjusted. The longer (100 s) measurement time is used to allow the direction of even the smallest measurable flows to be visible. The flow rate measurement range is 30 ml/h ml/h. The lower limit of measurement for the thermal dilution method is the theoretical lowest measurable value. Depending on conditions in the drillhole, these limits may not always prevail. Examples of possible disturbances are drilling debris entrained in the drillhole water, bubbles of gas in the water and high flow rates (some 30 L/min, i.e., ml/h or more) along the drillhole. If the disturbances encountered are significant, limits on practical measurements are calculated for each set of data.

12 8 Flow sensor B1 A B2 a) 200 P2 b) Power (mw) P1 Constant power in A c) dt(c) Thermal dilution method Temperature change in A Flow rate (ml/h) Time (s) Figure 2-3. Flow rate measurement. The device depth reference point in the PFL DIFF is situated at the upper end of the test section. When assessing the location of anomalies in the measured hole there are always some errors. They can be caused by the following reasons: 1. If the point interval is x, an error of ± x/2 can potentially occur assuming the point interval is small and rounded flow anomalies (see below) can be detected. 2. The length of the test section is not exact. The specified section length denotes the distance between the nearest upper and lower rubber sealing disks. Effectively, the section length can be larger. At both ends of the test section there are four rubber sealing disks. The distance between them is 5 cm. This will cause rounded flow anomalies: a flow may be detected already when a fracture

13 9 is situated between the four rubber sealing disks. These phenomena can cause an error of ± 0.05 m when the short step length (0.1 m) is used. A similar error can occur when the flow along the hole is measured. 3. The cable stretches under tension. When the probe is lifted upwards at c m the tension can be c. 175 kg. When it is lowered at the same depth, the tension can be c. 75 kg. This difference could cause a depth difference of c. 3 m between the measurements at depth of c m. The tension values here are estimates and can vary greatly depending on the device setup and hole properties. The total error in the worst case can be estimated. With a 0.1 m point interval the error would be: E = 0.05 m m + d where E is the total estimated error and d is the depth of the probe shown by the cable counter of the winch. Note that this is only a rough estimate and it is subject to change. It should also be noted that this is only one way of estimating the error. Experience has shown that when holes with length marks have been measured the error has been approximately 1 m at the depth of c m. Fractures nearly parallel with the hole may also be problematic. Fracture location may be difficult to define accurately in such cases.

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15 11 3 INTERPRETATION 3.1 Hydraulic head The absolute pressure sensor measures the sum of air pressure and the hydrostatic pressure in the drillhole. Air pressure is also registered separately. The hydraulic head along the drillhole under natural and pumped conditions can be determined from the measured data. The air pressure recorded at the site is first subtracted from the absolute pressure measured by the pressure sensor and the hydraulic head can then be calculated. The hydraulic head (h) at a certain elevation z is calculated using the following expression: h = (p abs - p b )/(ρ g) + z 3-1 where h is the hydraulic head (masl) p abs is absolute pressure (Pa) p b is barometric (air) pressure (Pa) ρ is unit density 1000 kg/m 3 g is standard gravity m/s 2 and z is the elevation at the measurement location (masl) Exact z-coordinates are important in hydraulic head calculation as a 10 cm error in the z-coordinate leads to a 10 cm error in the calculated head. 3.2 Transmissivity and hydraulic head The interpretation of data is based on Thiem s or Dupuit s formula, which describes a steady state and two-dimensional radial flow into the drillhole (Marsily 1986): h s h = Q/(T a) 3-2 where h is the hydraulic head in the vicinity of the drillhole and h s is the hydraulic head at the radius of influence (R), Q is the flow rate into the drillhole, T is the transmissivity of the test section, a is a constant that depends on the assumed flow geometry. For cylindrical flow, the constant a is: a = 2 π/ln(r/r 0 ) 3-3

16 12 where: r 0 is the radius of the drillhole and R is the radius of influence, i.e., the zone inside which the effect of pumping is felt. If measurements of flow rate are carried out using two levels of hydraulic head in the drillhole, i.e., natural and pump-induced heads, then the undisturbed (natural) hydraulic head and the transmissivity of the drillhole sections tested can be calculated. Equation 3-2 can be reformulated in the following two ways: Q s0 = T s a (h s - h 0 ) 3-4 Q s1 = T s a (h s - h 1 ) 3-5 where: h 0 and h 1 are the hydraulic heads in the drillhole at the test level, Q s0 and Q s1 are the measured flow rates in the test section, T s is the transmissivity of the test section and h s is the undisturbed hydraulic head in the tested zone far from the drillhole. In general, since very little is known about the flow geometry, cylindrical flow without skin zones is assumed. Cylindrical flow geometry is also justified because the drillhole is at a constant head, and no strong pressure gradients along the drillhole exist except at its ends. The radial distance R to the undisturbed hydraulic head h s is not known and must therefore be assumed. In this case, a value of 500 for the quotient R/r 0 is selected. The hydraulic head and the transmissivity in the test section can be deduced from the two measurements: h s = (h 0 -b h 1 )/(1-b) 3-6 T s = (1/a) (Q s0 -Q s1 )/(h 1 -h 0 ) 3-7 where: b = Q s0 -Q s1 The transmissivity (T f ) and hydraulic head (h f ) of individual fractures can be calculated provided that the flow rates at the individual fractures are known. Similar assumptions to those employed above must be used (a steady-state cylindrical flow regime without skin zones). h f = (h 0 -b h 1 )/(1-b) 3-8

17 13 T f = (1/a) (Q f0 -Q f1 )/( h 1 -h 0 ) 3-9 where: Q f0 and Q f1 are the flow rates at a fracture and h f and T f are the hydraulic head (far from the drillhole) and transmissivity of a fracture, respectively. Since the actual flow geometry and any skin effects are unknown, transmissivity values should only be considered as an indication of the prevailing orders of magnitude. As the calculated hydraulic heads do not depend on geometrical properties but only on the ratio of the flows measured at different heads in the drillhole, they should be less sensitive to unknown fracture geometry. A discussion of potential uncertainties in the calculation of transmissivity and hydraulic head can be found in (Ludvigson et al. 2002). 3.3 Fresh water head An important variable in hydrogeological characterization is the fresh water head. Traditionally, this is measured in drillholes using a tube filled with fresh water and open at both ends. It is important to note that the density of the water in the tube is not exactly 1000 kg/m 3 as the precise value is also dependent on temperature and compressibility - thermal expansion reduces the pressure measured with the absolute pressure sensor while compressibility increases it (Pöllänen 2002). A density correction was applied to the results obtained with the absolute pressure sensor to render them comparable with measurements made with a tube full of fresh water, and the effect of the two factors mentioned was eliminated by calculation. In this study all head values presented or used in calculations are fresh water heads. The fresh water head (h fw ) at a certain elevation z is calculated using the following expression: h fw = h + Corr Temp - Corr Compr 3-10 where h fw is the fresh water head (masl) h is the hydraulic head (masl) Corr Temp = Corrections for thermal expansion Corr Compr = Corrections for compressibility

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19 15 4 EQUIPMENT SPECIFICATION In the PFL DIFF method, the flow of groundwater into or out of a drillhole section is monitored using a flow guide which employs rubber sealing disks to isolate any such flow from the flow of water along the drillhole. This flow guide defines the test section being measured without altering the hydraulic head. Groundwater flowing into or out of the test section is guided to the flow sensor, and flow is measured using the thermal pulse and thermal dilution methods. Measured values are transferred to a computer in digital form. The range and accuracy of the sensors used is shown in Table 4-1. Type of instrument: Drillhole diameters: Length of test section: Method of flow measurement: PFL DIFF probe 56 mm, 66 mm and 76 mm (or larger) The flow guide length can be varied Thermal pulse and thermal dilution. Range and accuracy of measurement: See Table 4-1. Additional measurements: Winch: Depth determination: Logging computer: Software: Total power consumption: Temperature, Single point resistance, Electrical conductivity of water, Water pressure Mount Sopris Wna 10, 0.55 kw, conductors, Gerhard-Owen cable head. Based on a digital distance counter. PC (Windows XP) Based on MS Visual Basic kw depending on the type of pump employed Table 4-1. Range and accuracy of sensors. Sensor Range Accuracy Flow ml/h ± 10 % curr.value Temperature (central thermistor) 0 50 C 0.1 C Temperature difference (between outer C C thermistors) Electrical conductivity of water (EC) S/m ± 5 % curr.value Single point resistance (SPR) Ω ± 10 % curr.value Groundwater level sensor MPa ± 1 % full-scale Air pressure sensor hpa ± 5 hpa Absolute pressure sensor 0 20 MPa ± 0.01 % full-scale

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21 17 5 FIELD WORK AND RESULTS The field work was done in June For comparison earlier measurement results are also presented in appendices. The measurement program includes measurements in the depth intervals c. 24 m 64 m, 98 m 140 m and 396 m 424 m. Fracture-specific EC was measured at the depths of 28.4 m, 32.8 m, 33.6 m, 40.7 m, 42.7 m, 45.2 m, 48.8 m, 49.1 m, 52.6 m, 55.2 m, 56.5 m, 57.0 m, 59.0 m, 99.8 m, m, m, m and m fractures. Fracture-specific EC was measured at some additional fractures because the detected flow rate triggered an automatic EC logging procedure at these depths. These measurements were not used in the final fracture table (Appendices ). The activity schedule of the measurements is presented in Table 5-1. Technical information of drillhole OL-KR6 is presented in Table 5-2. Table 5-1. Measurements in drillhole OL-KR6. Activity schedule including Appendix numbers of results. Drillhole Date Activity Appendices OL-KR6 OL-KR EC and temperature in the drillhole with pumping. Detailed flow logging and EC from selected fractures. ( ) ( , , , , , ) Table 5-2. Technical information of drillhole OL-KR6. Drillhole Z- groundlevel (masl) Z-top of casing (masl) Inclination (degrees) Diameter (mm) Depth (m) Casing (m) OL-KR Pumping in the drillhole was started on 22 March Pumping rate and water level during pumping between February 2007 and September 2010 is presented in Figure 5-1. The water level in the drillhole before pumping was 1.63 m above sea level. The water level was constant c. 4.0 meters below sea level during the June 2010 measurement. The corresponding drawdown was c. 5.2 meters and pumping rate between c L/min 23 L/min. There were breaks in pumping on a few occasions. Pumping stopped due to power failures or other problems with the pump and this has caused the water level to rise, see Figure 5-1.

22 18 Water Level (masl) Pumping (L/min) Year-Month-Day Legend: Water level (masl) measured by Posiva Pumping rate measured by Posiva Pumping rate during flow logging Figure 5-1. Pumping rate and water level in drillhole OL-KR6 between February 2007 and September EC of drillhole water The electrical conductivity of drillhole water was measured downwards, see Appendix 1.1. Drillhole EC measurements were carried out once during the pumping period in June These measurements were carried out without the lower rubber disks. This measurement configuration is much more representative of drillhole water since the flow guide in its normal configuration (with both upper and lower rubber disks) may carry water with the probe making the results less representative, especially if the section length is long. The temperature of drillhole water has always been measured during the EC measurements, see Appendix 1.2. The EC values are temperature corrected to 25 C to make them more comparable with other EC measurements (Heikkonen et al. 2001). 5.2 Flow measurements Flow measurements were performed with a 0.5 m section length and with 0.1 m depth increments. The method gives the depth and the thickness of the conductive zones with a depth resolution of 0.1 m. The test section length determines the width of a flow anomaly of a single fracture. If the distance between flowing fractures is less than the section length, the anomalies will overlap resulting in a stepwise flow anomaly.

23 19 Measurements was carried out once in June 2010 in depth intervals c. 24 m 64 m, 98 m 140 m and 396 m 424 m, see Appendices The aim of these measurements was to find out whether there is long-term variation in flow rate. The time series of measured flows and water levels is presented in Appendices A table of the fracture specific EC and flows are shown in Appendices The flow rates of fractures increased after the December 2007 measurements due to the increased pumping rate, see Figure 5-1. The locations of fractures with water flow are marked with lines in the appendices of the flow measurements. A long line represents the location of a leaky fracture and a short line denotes that the existence of a leaky fracture is uncertain. 5.3 EC of fracture specific water The flow direction is always out of the fractures into the drillhole if the drillhole is pumped with a sufficiently large drawdown. This enables the electrical conductivity of fracture-specific water to be determined. Both the EC and the temperature of water flowing from the fractures were measured. Flow measurements make it possible to locate the fractures that have been selected for EC measurements. The probe is deployed so that the fracture to be tested is located within the test section. The probe is kept positioned over the selected fracture and measurement is continued allowing fracture-specific water to enter the test section. The time required to complete an EC measurement can be calculated automatically from the measured flow rate with the aim being to achieve adequate flushing of the volume of water within the test section. The computer controlling the measurement procedure is programmed to allow the water volume within the test section to be changed about three times. The results of these measurements on a depth scale are shown in Appendices The electrical conductivity of fracture-specific water was measured once from selected fractures between depth intervals c. 24 m 64 m, 98 m 140 m and 396 m 424 m. The EC transients (as a function of time) at these locations are presented in Appendices and Tables of the fracture specific EC are presented in Appendices Combined long-time period results have been presented in Appendices , time period between January 2004 and June The long-time period results include the flow rates of fracture, fracture-specific EC, pumping rate and water level. The results include pressure measurements made in drillhole OL-KR5 by Posiva (Ahokas et al. 2005, Tammisto et al. 2006, Klockars et al and Vaittinen et al. 2008). OL-KR5 is located close to OL-KR6. The long-term pumping has not caused any remarkable trends in the fracture specific EC. An exception in earlier measurements was the fracture at m during the measurement period between March 2006 and October 2006 when the minimum and maximum values were measured.

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25 21 6 CONCLUSIONS In this study groundwater flow and fracture-specific EC were measured during longterm pumping of OL-KR6. The EC and temperature of drillhole water were also measured. The aim of the measurements was to detect possible changes in the electrical conductivity of fracture-specific water and also changes in flow rates during the longterm pumping period. The flow rates of detected fractures increased after December 2007 measurements, because the pumping of the drillhole was increased. Pumping rate was increased in February 2008 from c. 15 L/min 16 L/min to c. 20 L/min 23 L/min. Measured fracture-specific EC and flow rate values in June 2010 were relatively constant when comparing time period between June 2009 and June In the earlier measurement periods there has been relatively large variation of fracture-specific water in the fracture at m (Appendix 7.4). The maximum fracture-specific EC value in the m fracture was measured in October-November There is also a corresponding change in the EC of the drillhole water at the same time. The EC value at this depth may be sensitive to pumping history including temporary pumping breaks.

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27 23 REFERENCES Ahokas, H., Klockars, J. & Lahdenperä, A Results of monitoring at Olkiluoto in , hydrology. Olkiluoto, Finland: Posiva Oy. Working Report Heikkonen, J., Heikkinen, E and Mäntynen, M Mathematical modelling of temperature adjustment algorithm for groundwater electrical conductivity on basis of synthetic water sample analysis (in Finnish). Helsinki, Posiva Oy. Working Report Klockars, J., Tammisto, E. & Ahokas, H Results of monitoring at Olkiluoto in 2006, hydrology. Olkiluoto, Finland: Posiva Oy. Working Report Ludvigson, J.-E., Hansson, K. and Rouhiainen, P Methodology study of Posiva difference flow metre in Drillhole KLX02 at Laxemar. SKB Rapport R Marsily, G., Quantitative Hydrogeology, Groundwater Hydrology for Engineers. Academic Press, Inc., London. Pekkanen, J., Pöllänen, J. and Rouhiainen, P Flow and electric conductivity measurements during long-term pumping of Borehole KR6, results from time period October October Helsinki, Finland: Posiva Oy. Working Report Pekkanen, J., Sokolnicki, M., Pöllänen, J Flow and Electric Conductivity measurements during long-term pumping of Borehole KR6, results from time period March January Olkiluoto, Finland: Posiva Oy. Working Report Pekkanen, J. and Pöllänen, J Flow and Electric Conductivity measurements during long-term pumping of drillhole OL-KR6, results from the time period between May 2006 and April Olkiluoto, Finland: Posiva Oy. Working Report Pekkanen, J Flow and Electric Conductivity measurements during long-term pumping of drillhole OL-KR6, results from the time period between October 2007 and November Olkiluoto, Finland: Posiva Oy. Working Report Pekkanen, J Flow and Electric Conductivity measurements during long-term pumping of drillhole OL-KR6, results from the time period between June 2009 and December Olkiluoto, Finland: Posiva Oy. Working Report Pöllänen, J. and Rouhiainen, P Difference flow and electric conductivity measurements at the Olkiluoto site in Eurajoki, Boreholes KR6, KR7 and KR12. Helsinki, Finland: Posiva Oy. Working Report Pöllänen, J. and Rouhiainen, P Flow and electric conductivity measurements during long-term pumping of borehole KR6 at the Olkiluoto site in Eurajoki. Helsinki, Finland: Posiva Oy. Working Report

28 24 Pöllänen, J Density and pressure of water in deep drillholes. Helsinki, Posiva Oy. Working Report (in Finnish). Rouhiainen, P Electric conductivity and detailed flow logging at the Olkiluoto site in Eurajoki, Boreholes KR1-KR11. Helsinki, Finland: Posiva Oy. Working Report Tammisto, E., Klockars, J. & Ahokas, H Results of monitoring at Olkiluoto in 2005, hydrology. Olkiluoto, Finland: Posiva Oy. Working Report Vaittinen, T., Klockars, J., Tammisto, E. & Ahokas, H Results of monitoring at Olkiluoto in 2007, hydrology. Olkiluoto, Finland: Posiva Oy. Working Report (in preparation)

29 25 Appendix 1.1 Olkiluoto, Drillhole OL-KR6 Electrical conductivity of drillhole water 0 Measured downwards Measured without lower rubber disks: With pumping With pumping With pumping With pumping With pumping With pumping With pumping Depth (m) Electrical conductivity (S/m, 25 o C)

30 26 Appendix 1.2 Olkiluoto, Drillhole OL-KR06 Temperature of drillhole water Measured downwards Measured without lower rubber disks: With pumping, With pumping, With pumping, With pumping, With pumping With pumping With pumping Depth (m) Temperature ( o C)

31 27 Appendix 2.1 Fracture specific electrical conductivity, flows from the fracture to the drillhole, water level and pumping rate Olkiluoto, drillhole OL-KR6 0.3 Pumping rate, measured by Posiva Pumping rate during flow logging Water Level (masl) Depth of fracture 28.4 m 32.8 m 33.6 m 40.7 m 42.7 m 45.2 m 47.2 m (measured only flow rate) 48.8 m Electrical conductivity (S/m, 25 o C) Flow (ml/h) Pumping rate OL-KR6 (L/min) Year-Month-Day Water Level OL-KR6 (masl)

32 28 Appendix 2.2 Fracture specific electrical conductivity, flows from the fracture to the drillhole, water level and pumping rate Olkiluoto, drillhole OL-KR6 0.4 Pumping rate, measured by Posiva Pumping rate during flow logging Water Level (masl) Depth of fracture 49.1 m 52.6 m 55.2 m 56.5m 57.0m 59.0 m 54.4m (Measured only flow rate) Electrical conductivity (S/m, 25 o C) Flow (ml/h) Pumping rate OL-KR6 (L/min) Year-Month-Day Water Level OL-KR6 (masl)

33 29 Appendix 2.3 Fracture specific electrical conductivity, flows from the fracture to the drillhole, water level and pumping rate Olkiluoto, drillhole OL-KR6 3 Pumping rate, measured by Posiva Pumping rate during flow logging Water Level (masl) Depth of fracture 99.8 m m (measured only flow rate) m m m m Electrical conductivity (S/m, 25 o C) Flow (ml/h) Pumping rate OL-KR6 (L/min) Year-Month-Day Water Level OL-KR6 (masl)

34 30 Appendix 3.1 Flow rate Eurajoki, Olkiluoto, drillhole OL-KR06, with pumping section 0.5 m, step 0.1 m Depth (m) Flow rate (ml/h)

35 31 Appendix 3.2 Flow rate Eurajoki, Olkiluoto, drillhole OL-KR06, with pumping section 0.5 m, step 0.1 m Depth (m) Flow rate (ml/h)

36 32 Appendix 3.3 Flow rate Eurajoki, Olkiluoto, drillhole OL-KR6, with pumping section 0.5 m, step 0.1 m Depth (m) Flow rate (ml/h)

37 33 Appendix 3.4 Flow rate Eurajoki, Olkiluoto, drillhole OL-KR06, with pumping section 0.5 m, step 0.1 m Depth (m) Flow rate (ml/h)

38 34 Appendix 3.5 Flow rate Eurajoki, Olkiluoto, drillhole OL-KR6, with pumping section 0.5 m, step 0.1 m Depth (m) Flow rate (ml/h)

39 35 Appendix 4.1 Electrical conductivity of drillhole water Eurajoki, Olkiluoto, drillhole OL-KR6 During flow measurements Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Depth (m) o Electrical conductivity (S/m, 25 C)

40 36 Appendix Electrical conductivity of drillhole water Eurajoki, Olkiluoto, drillhole OL-KR6 During flow measurements Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Depth (m) Electrical conductivity (S/m, 25 o C)

41 37 Appendix 4.3 Electrical conductivity of drillhole water Eurajoki, Olkiluoto, drillhole OL-KR6 During flow measurements Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.5 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Measured downwards with 0.1 m depth increments in the drillhole, Last in time series, fracture specific water, Depth (m) o Electrical conductivity (S/m, 25 C)

42 38 Appendix 5.1 Olkiluoto, drillhole OL-KR06 Fracture-specific Flow, EC and Temperature results by date Water level and Air pressure results by date Air pressure (kpa) When the probe is moved When the probe is stopped on a fracture Average of 10 last EC measurements, fracture specific water, (Depth = Upper end of section) Water level (masl) Temperature ( o C) Electrical conductivity (S/m) (25 o C) m 28.1 m 32.5 m 33.3 m Flow (ml/h) : : :30 Year-Month-Day / Hour:Minute :00

43 39 Appendix 5.2 Olkiluoto, drillhole OL-KR06 Fracture-specific Flow, EC and Temperature results by date Water level and Air pressure results by date Air pressure (kpa) When the probe is moved When the probe is stopped on a fracture Average of 10 last EC measurements, fracture specific water, (Depth = Upper end of section) Water level (masl) Temperature ( o C) Electrical conductivity (S/m) (25 o C) m 42.3 m 44.8 m 48.5 m 48.9 m 52.3 m 54.9 m Flow (ml/h) : : :30 Year-Month-Day / Hour:Minute :00

44 40 Appendix 5.3 Olkiluoto, drillhole OL-KR06 Fracture-specific Flow, EC and Temperature results by date Water level and Air pressure results by date Air pressure (kpa) When the probe is moved When the probe is stopped on a fracture Average of 10 last EC measurements, fracture specific water, (Depth = Upper end of section) Water level (masl) Temperature ( o C) Electrical conductivity (S/m) (25 o C) m 56.7 m 58.8 m 62.5 m 99.5 m Flow (ml/h) : : :00 Year-Month-Day / Hour:Minute :30

45 41 Appendix 5.4 Olkiluoto, drillhole OL-KR06 Fracture-specific Flow, EC and Temperature results by date Water level and Air pressure results by date Air pressure (kpa) When the probe is moved When the probe is stopped on a fracture Average of 10 last EC measurements, fracture specific water, (Depth = Upper end of section) Water level (masl) Temperature ( o C) Electrical conductivity (S/m) (25 o C) Flow (ml/h) m m : : :30 Year-Month-Day / Hour:Minute :15

46 42 Appendix 5.5 Olkiluoto, drillhole OL-KR06 Fracture-specific Flow, EC and Temperature results by date Water level and Air pressure results by date Air pressure (kpa) When the probe is moved When the probe is stopped on a fracture Average of 10 last EC measurements, fracture specific water, (Depth = Upper end of section) Water level (masl) Temperature ( o C) Electrical conductivity (S/m) (25 o C) Flow (ml/h) m :30 Year-Month-Day / Hour:Minute :00

47 43 Appendix 5.6 Olkiluoto, drillhole OL-KR06 Fracture-specific Flow, EC and Temperature results by date Water level and Air pressure results by date Air pressure (kpa) When the probe is moved When the probe is stopped on a fracture Average of 10 last EC measurements, fracture specific water, (Depth = Upper end of section) m Electrical conductivity Temperature (oc) (S/m) (25 oc) Water level (masl) Flow (ml/h) :00 :00 :00 :00 :00 12:0 8 0: 9 0: Year-Month-Day / Hour:Minute

48 Olkiluoto, drillhole OL-KR6, Table of fracture-specific EC and flow rates Up Sec = Upper end of section during fracture specific EC (m) Low Sec = Lower end of section during fracture specific EC (m) Depth = Depth from the reference depth to the fracture (m) HeadP = Head in the drillhole with pumping (meter above sea level) FlowP = Flow from the fracture to the drillhole with pumping (ml/h) StartDate EC = Start of EC-time serie (DD:MM:YYYY) StartTime EC = Start of EC-time serie (hh:mm:ss) Time = Total time of the fracture-ec measurement (s) Vol Am = The amount of times the water volume has changed in the measurement section. The measurement time for fracture EC is based on a single measured flow rate. The interpreted fracture flow on the other hand is based on several measurements and is therefore different. This can lead to Vol Am values less than 3. Temp = Temperature of water Corr EC = Electrical conductivity of water with temperature correction (average of 10 last points in time series) (S/m at 25 C) TDS = Total dissolved solids of fracture specific water (average of 10 last points in time series) (g/l at 25 C) Ch % = The change in the EC value during the last sixth time interval of the EC measurement (%). The time last sixth time interval is Time/6 seconds long. Total Q = Total water flow from the fracture from the beginning of pumping until the end of the fracture EC measurement (L) assuming the fracture flow is constant. 44 Appendix 6.1 StartTimeEC Time Vol Am Temp Corr EC TDS Ch % Total Q Comments Depth HeadP FlowP StartDate EC Low Sec Upp Sec :58: E :12: E :44: E :58: E :01: E :28: E :28: E+06

49 45 Appendix 6.2 Upp Sec Low Sec Depth StartDate HeadP FlowP EC StartTimeEC Time Vol Am Temp Corr EC TDS Ch % Total Q Comments :44: E :15: E :42: E :04: E :52: E :17: E :01: E :16: E :27: E :22: E :02: E+05