Hot Dry Rock Energy Project Soultz-sous-Forêts BRGM contribution

Transcription

1 Hot Dry Rock Energy Project Soultz-sous-Forêts BRGM contribution Progress Report BRGM/RP FR october 2003

2 Hot Dry Rock Energy Project Soultz-sous-Forêts BRGM contribution Progress Report BRGM/RP FR october 2003 Project carried out as part of research on behalf of the European Community n ENK5-CT S. Gentier With the collaboration of A. Genter, B. Sanjuan, B. Bourgine, C. Dezayes, A. Hosni, J.P. Breton, N. Nicol, J.P. Quinquis, C. Crouzet, G. Braibant, M. Brach, A. Moussay, J.C. Foucher, F. Jouin

3 Keywords: HFR geothermal system, Hydromechanical modelling, Tracer test, Fluid geochemistry, Geological monitoring, Well logging, HAC analysis. In bibliography, this report should be cited as follows: Gentier S., with the collaboration of Genter A., Sanjuan B., Bourgine B., Dezayes C., Hosni A., Breton J.P., Nicol N., Quinquis J.P., Crouzet C., Braibant G., Brach M., Moussay A., Foucher J.C., Jouin F. (2003) «Hot Dry Rock Energy» Project (Soultz-sous-Forêts) BRGM contribution (progress report). BRGM/RP FR, 51 p., 24 Fig., 15 Tables. BRGM, 2003, all rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of BRGM. 2 BRGM/RP FR

4 Synthesis I n the framework of the European project «Hot Dry Rock Energy», BRGM contributes to the scientific activities of the first phase of construction of a Scientific Pilot Plant on the site of Soultz-sous-Forêts. Such a Scientific Pilot Plant will be built in two phases over three years each. Work presented in this report corresponds to reporting period from April 2003 to September The contractual part of the BRGM contribution is focused on three main packages (WP): - WP8: Thermo-hydro-mechanical modelling of the reservoir/heat exchanger; - WP10: Typology of continental HDR/HFR systems in Europe; - WP11: Strategy for resources development of European HDR/HFR systems. The BRGM contribution has been mainly focused on the contractual part with: - analysis of the fracture network in GPK-3 and modelling of the deep hydraulic stimulation of GPK-2 (Workpackage 8); - evaluation of the Eger graben and the Strymon graben (Workpackage 10); - some estimations of the potential HFR/HDR resource area of central Europe (Workpackage 11). The tasks which have been performed in the framework of the accompanying scientific work during this reporting period have been focused on geochemical works in accompanying of the hydraulic stimulation of GPK-3 and hydraulic tests in GPK-2. The 3D hydromechanical modelling of the hydraulic stimulation of GPK-2 seems qualitatively in good agreement with the measurements in spite of the few precise geological data available from the lower part of the well GPK-2. To prepare it, a work on the geology and the fracture network met in GPK-3 has been done (1) to evaluate the fracture system in GPK-3 based on the continuous borehole image logs available in the well and (2) to estimate which part of the fracture system is able to be connected geometrically between GPK-2, GPK-3 and the future well GPK-4. Tracer injections are another mean to establish the potential connections between the wells and to understand the progressive migration of the injected fluid in each well. Data obtained from the geochemical monitoring of the fluid produced from GPK-3 suggested the existence of a direct hydraulic connection between GPK-2 and GPK-3, already existing before any stimulation of GPK-3. The monitoring of the two tracers injected in GPK-3 in the fluid produced from GPK-2 gave complementary information. Assuming some hypothesis, it can be then deduced from the nitrate, that only around 7 days have been necessary to this tracer to go from GPK-3 to GPK-2. At several stages of the production tests, estimation of the percentage of freshwater can be done by analysing the various tracers injected during the three last year and can help to the understanding of the fluid migration. These data BRGM/RP FR 3

5 imply that the volume of recovered fluid from GPK-2 during some 26 days represents approximately 10% of the total volume of fluid injected into GPK-3 in At another scale, work on the Typology of continental HDR/HFR systems in Europe are going on by the evaluation on of the Eger graben and the Strymon graben. The Rhine graben and the Tuscany maps are in the digitising process. Moreover, some estimations of the potential HFR/HDR resource area of central Europe have been done. 4 BRGM/RP FR

6 Sommaire 1. Introduction Project GEIE/BRGM WP8: Thermo-hydro-mechanical modelling of reservoir/heat exchanger (T.H.M. Modelling) Fracture network in GPK Hydromechanical modelling of the stimulation of GPK Publications and Meetings WP10: Typology of continental HDR/HFR systems in Europe Results Meetings and exchanges WP11: Strategy for resource development of European HDR/HFR systems Accompanying Scientific work Geochemical monitoring of the fluid produced from the GPK-3 well (March 2003) Injection of the 1,6-nds and NaNO 3 tracers into GPK-3 (May - June 2003) Injection of 1,6-nds Injection of NaNO Geochemical monitoring of the fluid produced from the GPK-2 well (June - July 2003) Conclusion References Acknowledgements BRGM/RP FR 5

7 Liste des figures Fig. 1 - Cumulative fracture density versus depth in the well GPK-3 based on UBI log interpretation Fig. 2 - Stereographic projections (Schmidt lower hemisphere) of the fracture data collected in the Soultz wells Fig. 3 - Geological cross-section between the deep wells at Soultz Fig. 4 - Measured curve of pressure according to the flow rate in the lower part of GPK-2 (2000) (Baria et al., 2001) Fig. 5 - a) Geometry of the model and b) presentation of the fracture network in the lower part of GPK Fig. 6 - Initial and boundary hydro-mechanical conditions assumed in the model Fig. 7 - Distribution of the pressures in the fracture plane F1 at the initial state Fig. 8 - Overpressure conditions used in the simulation of the hydraulic stimulation test performed in the lower part of the well GPK Fig. 9 - Simulation of the hydraulic test performed in the lower part of GPK-2 in Fig Distribution of the hydraulic apertures calculated in the model for the fracture F1 in the GPK-2 well (stimulation test in 2000) Fig Distribution of the hydraulic apertures calculated in the model for the fracture F4 in the GPK-2 well (stimulation test in 2000) Fig Geological map of the Eger graben Fig Geological map of the Strymon graben Fig Thematic map of the Strymon graben Fig a) Geographical map; b) Temperature extrapolated at 5 km depth; c) Location of the sediment thickness in the Pannonian basin Fig Potential area for HFR resource in eastern Europe based on temperature maps for a hard rock accessible by drilling between 2 and 3 km depth Fig Geochemical monitoring of the fluid discharged from the GPK-3 well (March 2003): analytical results of the organic tracers (1,5-nds and 2,7- nds) Fig Estimation of the proportions of freshwater injected into GPK-2 in 2000 and 2003, relative to the total mass of fluid discharged from the GPK-3 well (March 2003), using the concentrations of Cl and organic tracers (1,5 and 2,7-nds) Fig Geochemical monitoring of the fluid discharged from the GPK-2 well (from 26/06 to 9/07/2003): analytical results of the NaNO 3 tracer obtained using the colorimetric technique on site BRGM/RP FR

8 Fig Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): analytical results of the organic tracers injected into GPK-2 in 2000 (Na-benzoate and 1,5-nds) Fig Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): analytical results of the 2,7-nds tracer injected into GPK-2 in Fig Estimation of the proportions of the freshwater injected into GPK-2 in 2003, relative to the total mass of fluid discharged from this well (from 11/06 to 9/07/2003), using the concentrations of 2,7-nds Fig Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): analytical results of the 1,6-nds tracer injected into GPK-3 in Fig Estimation of the proportions of the fluid injected into GPK-3 in 2003, relative to the total mass of fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003), using the concentrations of 1,6-nds Liste des tableaux Table 1 - Planning of the BRGM contribution... 9 Table 2 - Geometrical properties of the main fractures in the lower part of GPK Table 3 - Mechanical properties of the blocs in the model Table 4 - Hydro-mechanical properties of the fractures in the model Table 5 - Percentage of flow injected through the fractures obtained by the model Table 6 - Concentrations of 2,7-nds during its injection into the GPK-2 well in Table 7 - Geochemical monitoring of the fluid discharged from the GPK-3 well (march 2003): results of some chemical analyses compared to estimated data Table 8 - Geochemical monitoring of the fluid discharged from the GPK-3 well (March 2003): analytical results of the organic tracers and estimation of the proportions of freshwater injected into GPK-2 in 2000 and 2003 relative to the total mass of fluid discharged from GPK-3, using the concentrations of Cl, Br and organic tracers (1,5-nds and 2,7-nds) Table 9 - Tracer concentrations in the fluid injected into GPK-2 (June 3-5, 2003) and into GPK-3 (from 27/05 to 9/07/2003) Table 10 - Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): on site measurements BRGM/RP FR 7

9 Table 11 - Geochemical monitoring of the fluid discharged from GPK-2 (from 26/06 to 9/07/2003): NO 3 analysed by colorimetry on site and by Ionic Chromatography (IC) at BRGM laboratory Table 12 - Analytical results obtained on a fluid sample collected from GPK-2 with addition of a NO 3 solution in order to have a NO 3 concentration of 25 mg/l in this sample Table 13 - Analytical results of nitrate obtained using the colorimetric technique Table 14 - Analytical results of nitrate obtained using the colorimetric technique Table 15 - Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): tracer analyses and estimation of the proportions of fluid injected into GPK-2 and into GPK-3 relative to the total mass of fluid discharged from GPK-2, using the concentrations of Cl and organic tracers BRGM/RP FR

10 1. Introduction I n the framework of the European project «Hot Dry Rock Energy», BRGM contributes to the scientific activities of the first phase of construction of a Scientific Pilot Plant on the site of Soultz-sous-Forêts. Such a Scientific Pilot Plant will be built in two phases over three years each. BRGM contribution to the European project is composed of a contractual part cofunded by European Community via the EEIG, which concerns the three following Work-Packages: - WP8 : Thermo-hydro-mechanical modelling of the reservoir/heat exchanger; - WP10 : Typology of continental HDR/HFR systems in Europe; - WP11 : Strategy for resources development of European HDR/HFR systems. In parallel, BRGM contributes on its own funds to scientific accompanying work which consists to research work in relationship with in-situ operations. The four main topics are the following: - Geological and geochemical monitoring during drilling operations; - Updating of the structural model; - Geochemistry of geothermal fluids; - Tracer tests contributing to the hydraulic understanding of the geothermal system. During the period of the present reporting going from April 2003 to September 2003, the main tasks on which BRGM has worked are summarised in the following table (Table 1) TASKS April May June July August Sept. Oct. I. Project BRGM/GEIE WP8 : Thermo-Hydro-mechanical modelling WP10 : Typology of continental HDR/HFR systems in Europe WP11: Strategy for ressources development II. Accompanying scientific work 1.1 Geochemical monitoring of production test in GPK3 1.2 Geochemical monitoring of stimulation of GPK3 1.3 Geochemical monitoring of production test in GPK2 Table 1 - Planning of the BRGM contribution. The BRGM contribution has been mainly focused on the contractual part with: - analysis of the fracture network in GPK-3 and modelling of the deep hydraulic stimulation of GPK-2 (Workpackage 8); - evaluation of the Eger graben and the Strymon graben (Workpackage 10); BRGM/RP FR 9

11 - some estimations of the potential HFR/HDR resource area of central Europe (Workpackage 11). The tasks which have been performed in the framework of the accompanying scientific work during this reporting period have been focused on geochemical works in accompanying of the hydraulic stimulation of GPK-3 and hydraulic tests in GPK BRGM/RP FR

12 2. Project GEIE/BRGM 2.1. WP8: THERMO-HYDRO-MECHANICAL MODELLING OF RESERVOIR/HEAT EXCHANGER (T.H.M. MODELLING) Participants: A. Hosni, S. Gentier, A. Genter, C. Dezayes, B. Bourgine. The objective of this work-package was to use and interpret the new data obtained from the drilling of the new bore-holes and their stimulation. Analysis of geological and structural data from GPK-3 has been undertaken and a first hydromechanical modelling of the deep hydraulic stimulation of GPK-2 has been done. Consequently, the two main tasks during this period of reporting are the following: - analysis of the fracture network in GPK-3; - modelling of the deep hydraulic stimulation of GPK Fracture network in GPK-3 Participants: Ch. Dezayes, B. Bourgine, A. Genter, G. Homeier, G.R. Hooijkass, E. Maqua. The objective of this work is (1) to evaluate the fracture system in GPK-3 based on the continuous borehole image logs available in the well and (2) to estimate which part of the fracture system is able to be connected geometrically between GPK-2, GPK-3 and the future well GPK-4. The collected fracture data sets could be used as input data in the general THM modelling procedure. a) Fracture network analysis in GPK-3 Based on the UBI logs (Ultrasonic Borehole Imager), an exhaustive fracture analysis has been done within the GPK-3 well. BRGM worked in the most vertical part of the GPK-3 well (1,420-2,950 m), and in the open hole section (4,580-5,100 m). Personal from SWBU * interpreted the section ranging between 2,950 and 4,580 m depth. In terms of cumulative fracture density versus depth, the main results are illustrated in Figure 1. The lower is the slope, the higher is the fracture density. In the upper part of the well (1,420-2,950 m), two sections are evidenced : a high fracture density zone between 1,420 and 1,825 m, and a moderate fracture density zone between 1,825 and 2,950 m. Previous studies done at Soultz shown that the upper part of the granite massif is always the most fractured section (Genter et al., 1997). In the open hole section (4,580-5,100 m), the fracture density is variable with some zones showing some high fracture concentrations which alternated with some poorly fractured zones. In terms of fracture orientation (Fig. 2), the upper part of the GPK-3 well is characterized by a main fracture set oriented N10E and dipping eastward (N10E75E). Two secondary sets dipping westward occur (N30E70W, N170E70W). The lower part * Stadt Werke Bad Urach. BRGM/RP FR 11

13 of the well is characterized by only a main fracture set oriented N0E75W, but the data are highly scattered around this major fracture set. Fig. 1 - Cumulative fracture density versus depth in the well GPK-3 based on UBI log interpretation. b) Geometrical fracture modelling In order to try to find some geometrical connections between the deep wells, namely GPK-2, GPK-3 and GPK-4, a modelling procedure has been developed in the vertical part of GPK-3 between 1,450 and 3,000 m depth (Maqua, 2003). In a first step, we tried to identity the major fractures visible on the image logs on both GPK-2 and GPK-3 wells. In a second step, we tried to correlate those major fractures observed in a given well, for instance GPK-3, and their geometrical extension in the second well, for instance GPK-2. If the intersection of the extrapolated fracture plane matches with an actual fracture visible on the borehole log, we validated the geometrical extension. If not, it means that, for example, the fracture extension is shorter than the interwell distance or its orientation is not constant. All the different geometrical possibilities are reported in Maqua (2003). The most easily correlated fractures between GPK-3 and GPK-2 are located in the most vertical section of the wells, between 1,550 and 2,090 m depth. Deeper, the geometrical correlations are less well constrained mainly because the interwell distance increases. 12 BRGM/RP FR

14 Fig. 2 - Stereographic projections (Schmidt lower hemisphere) of the fracture data collected in the Soultz wells. c) Geological model of the Soultz site In order to validate the geological model done on site by Dezayes et al. (2003), a detailed petrographical analysis of about 100 thin sections have been done (Hooijkaas, 2003). The main results are summarised in the geological cross-section (Fig. 3). BRGM/RP FR 13

15 Sedimentary cover Porphyritic MKF-rich granite with paleoweathering Porphyritic MKF-rich granite Porphyritic MKF-rich granite with intense vein alteration bt-amf rich granite gradually becoming standard granite with depth 2-mica granite Fig. 3 - Geological cross-section between the deep wells at Soultz Hydromechanical modelling of the stimulation of GPK-2 The hydromechanical modelling of the stimulation of the three deep wells is done with a numerical code developed and tested in the framework of previous ADEME conventions (Gentier et al., 2001, 2002, 2003). 14 BRGM/RP FR

16 a) Code presentation The code allows us to take account a realistic geometry of the fracture network intersecting the blocks, which are considered to be deformable. The fractures are assigned normal and tangential non constant stiffness, and are deformed according to a continuously yielding law of behaviour with the possibility of damage to the edges. A threshold is defined for the elastic deformations from an initial friction angle. The residual behaviour is also defined by a residual friction angle. The blocks are assumed to be impermeable and to display elastic behaviour. Fluid flow occurs exclusively through the fracture network and obeys to a cubic law. The 3DEC-FLO software employed to make the coupled hydro-mechanical calculations is based on a discretization of the blocks into tetrahedral elements and the fractures into elementary domains. The modification of the pressure field results in a modification of the actual stresses applied to the surrounding formations, which may themselves cause changes in the openings of the fractures and hence of the pressure field. Since the calculation method in 3DEC-FLO is incremental with pre-set time steps, equilibrium in the model is reached when the pressure and stress fields show no longer change between two consecutive time steps. b) Objective In this report, we present some results obtained from the study of the hydraulic stimulation test conducted in 2000 in the lower part of the well GPK-2 located between 4,000 and 5,000 m of depth (Fig. 4). Fig. 4 - Measured curve of pressure according to the flow rate in the lower part of GPK-2 (2000) (Baria et al., 2001) BRGM/RP FR 15

17 The aim of the study is to analyse the hydraulic behaviour measured in the well by using a numerical tool based on an approach which takes into account the hydromechanical coupled processes. As a recall, in 3DEC-FLO, the mechanical deformations in the normal direction (U n ) and hydraulic apertures (a) are related by the expression above in which (a 0 ) represent the hydraulic aperture at zero normal stress: a = a 0 + U n (1) Also, the fractured granitic basement is modelled in the calculation code as blocs assembly separated by real discontinuities. This characteristic of 3DEC-FLO offer the possibility to understand better the mechanism which could probably be responsible of the increase in the permeability of the fractured rock mass. c) Presentation of the model The first step is to construct the model geometry corresponding to the fractured media in the lower part of the well GPK-2. Thus, the first model is represented by the fracture network which contains mainly four fractures interpreted from the data (Table 2). Fracture N Depth (m) Dip ( ) Dip Direction ( ) F1 4, F2 4, F3 4, F4 4, Table 2 - Geometrical properties of the main fractures in the lower part of GPK-2. Each fracture is free to intersect the others in the model and the tri-dimensional extension of the fractures are limited only by the size assumed for the model (Fig. 5). a Fig. 5 - a) Geometry of the model and b) presentation of the fracture network in the lower part of GPK-2. b 16 BRGM/RP FR

18 The definition of initial and boundary conditions is needed for the model in order to establish the reference state from which the effect of the injection pressures on the hydro -mechanical behaviour is studied (Fig. 6). This stage is necessary when we wish to assess the volume of injected flows due to the imposed overpressures in the well. σ v σ H P i = ρ g z σ h Nord Est Fig. 6 - Initial and boundary hydro-mechanical conditions assumed in the model. Hence, we assume as initial stresses in the model the natural stress field established by the expression below for the depth comprises between 1,450 and 3,500 m (Klee and Rummel, 1993): σ h = 15,8 + 0,0149 (z-1458) σ H = 23,7 + 0,0336 (z-1458) [en MPa] (2) σ v = 33,8 + 0,0255 (z-1377) where σ h and σ H are representing respectively the minimal and maximal horizontal principal stress; and σ v the vertical principal stress. We also assume that the distribution of the initial pressures in the fracture network is obeying to a hydrostatic field as indicated in the equation below: P = ρ * g * z (3) where ρ represent the density of water. As a hydro-mechanical boundary conditions, we assume a hydrostatic pressure and no displacement at the boundaries of the model. The hydro-mechanical properties which are taken into account for the blocs and for the fractures are summarized below (Tables 3 and 4) and were established with the model during the modelling of the hydraulic stimulation test performed in the upper part of the well GPK-2 (Gentier et al., 2003b). BRGM/RP FR 17

19 Density (kg/m 3) Young Modulus (MPa) Poisson s ratio υ Blocs 2,680 52,000 0,29 Table 3 - Mechanical properties of the blocs in the model. K n,min (Mpa/m) K n,max (Mpa/m) K s,min (Mpa/m) K s,max (Mpa/m) Initial Friction Resid. Friction Roughness a res a 0 a max Fracture 80, ,000 80, , mm 10-8 m m 10-3 m Table 4 - Hydro-mechanical properties of the fractures in the model. d) Results At the beginning we can verify in the model that the distribution of the fracture pressures is obeying to an hydrostatic field as it was assumed above, the example of the fracture F1 is shown as an illustration (Fig. 7). Fig. 7 - Distribution of the pressures in the fracture plane F1 at the initial state. After that, the simulation of the hydraulic test is carried out in the model by adding an overpressure ( P) in the open part of the well and by calculating the flow rate injected throughout the fracture network when the hydro-mechanical equilibrium is reached (Fig. 8). 18 BRGM/RP FR

20 Well Injection under P = P i + D P Fig. 8 - Overpressure conditions used in the simulation of the hydraulic stimulation test performed in the lower part of the well GPK-2. The overpressures ( P) considered in this study are given below and we can observe that the first step which corresponds to an overpressure around 12 MPa was subdivided in this simulation into 4 successive stages characterized by the application of overpressures increasing from 3 MPa to 11,5 MPa: ( P) : 3 MPa, 6 MPa, 9 MPa, 11,5 MPa, 12,5 MPa and 14 MPa. The first results obtained from the model are presented below: - an overpressure ( P) close to 14 MPa is needed in the model for the injection of a flow rate around 30 l/s (Fig. 9). The calculated value of ( P) seems higher in comparison to the measured value which is around 12 MPa (Fig. 4); 16 Overpressure_ P (MPa) Model Measures Flow rate (l/s) Fig. 9 - Simulation of the hydraulic test performed in the lower part of GPK-2 in BRGM/RP FR 19

21 - in term of percentage of flow, the lower zone is most favourable to the circulation of fluid since more than 70% of the injected fluid carried out through the fracture F4 (Table 5); Fracture N Overpressure Percentage of Overpressure Percentage of Overpressure Percentage of P=11,5MPa flow per fracture P=12,5MPa flow per fracture P=14MPa flow per fracture Flow rate (l/s) Flow rate (l/s) Flow rate (l/s) F1 1,4 8 1,95 9 2,84 9 F2 0,67 4 0,91 4 5,2 16 F3 0,64 3 0,8 4 1,04 3 F4 15, , ,6 72 Cumulated Flow rate (l/s) 18, , , Table 5 - Percentage of flow injected through the fractures obtained by the model. - the maximum of the hydraulic aperture is reached locally in the fracture F1 in the zone located in the nearest well (Fig. 10) whereas the maximum aperture appears in a large zone covering the total area of the fracture F4 (Fig. 11) which gives an explanation to the high flow rate differences calculated for the two fractures; Fig Distribution of the hydraulic apertures calculated in the model for the fracture F1 in the GPK-2 well (stimulation test in 2000). 20 BRGM/RP FR

22 Fig Distribution of the hydraulic apertures calculated in the model for the fracture F4 in the GPK-2 well (stimulation test in 2000). - the comparison between the results obtained from the flow log performed in the well and those obtained by the model showed that the later slightly over-estimates the percentage of flow calculated in the lower zone (Fracture F4 in the model) and slightly under-estimates the injected flow in the higher zones (F1, F2 and F3). Indeed, the flow log showed that around 69% of fluids are circulating through the lower zone (Fracture F4 and deeper), 22% through the fracture F3, and 9% in the upper part through the upper zone (Fractures F1 and F2). The differences could be due to uncertainties coming from the definition of the geometrical parameters of the fractures which have a great influence on the shearing mechanism induced in the fracture planes by the in situ stresses as it was established in the last studies (Gentier et al., 2003a; 2003b). Indeed, the fracture parameters are not determined from direct observations (diagraphies) as it was generally done, but they was determined from few indirect information of various kinds. In the lower part, more details must be introduced in the model. e) Conclusion This first model seems qualitatively going in the way of the most part of the fluid injected in the lower part of the well as it is shown by the measurements in spite of the few precise geological data introduced in the lower part of the well GPK-2. First, to better calibrate the model it appears that it is necessary in the future to define with a high precision the geological data (fractures). However, the study of the influence of the fracture orientations on the modelled hydro-mechanical behaviour obtained in the lower part of the GPK-2 during the hydraulic stimulation test performed in 2000 is currently in progress. BRGM/RP FR 21

23 Publications and Meetings During the reporting period: - A. Genter attended a conference on September 2003, the Siena conference (Italy); - S. Gentier attended a workshop on EGS Systems and a conference on June 2003 in Cambridge (USA), the 39 th US Rock Mechanic Symposium; - A. Hosni attented a conference on October 2003 in Stockholm (Sweden), the International Conference on Coupled T-H-M-C Processes in Geosystems. G. Homeier from SWBU visited our laboratory in BRGM on may Several papers or reports were published during the reporting period (see the references listed below). Gentier S., Hosni A., Genter A., Billaux D., Dedecker F., Rachez X. (2003) - Hydraulic stimulation of geothermal wells in HFR systems: Approach based on 3D hydromechanical modeling. 39 th US Rock Mechanic Symposium - Cambridge, June Hosni A., Gentier S., Genter A., Riss J., Billaux D., Dedecker D. (2003) - Coupled THM Modeling of the stimulated permeable fractures in the near well at the Soultz-sous- Forêts site (France). In: GeoProc 2003 : International Conference on Coupled T-H- M-C Processes in Geosystems - Stockholm /10/2003. Dezayes Ch., Genter A., Homeier G., Degouy M., Stein G. (2003) - Geological study of GPK-3 HFR borehole (Soultz-sous-Forêts, France). BRGM/RP FR, 128 p. Dezayes Ch., Genter A., Maqua E., Stein G. (2003) - Granite intrusions and fracture system in the Soultz HFR geothermal reservoir. Structures in the Continental Crust and Geothermal Resources, Siena (Italy), Sept., 2003, p Hooijkaas G.R. (2003) - Petrography and fracture alteration of GPK-3 HFR borehole (Soultz-sous-Forêts, France) and integration with other Soultz wells. Free University, Amsterdam, Holland, October Maqua E. (2003) - Analyse de la fracturation à partir d images de paroi dans le forage géothermique GPK-3 de Soultz-sous-Forêts (Alsace, France). Rapport de stage BRGM, juin 2003, Université de Savoie WP10: TYPOLOGY OF CONTINENTAL HDR/HFR SYSTEMS IN EUROPE Participants: A. Genter, J.P. Breton, N. Nicol, Ch. Dezayes, J.P. Quinquis. During the reporting period, the evaluation of the Eger graben and the Strymon graben have been done. The Rhine graben and the Tuscany maps are in the digitising process. 22 BRGM/RP FR

24 Hot Dry Rock Energy project: Soultz-sous-Forêts Fig Geological map of the Eger graben. BRGM/RP FR 23

25 Results The Eger graben which is located mainly in Czech Republic, is a tertiary graben belonging to the west European rift system as the Rhine graben. This graben is mainly oriented ENE-WSW and bounded by regional normal faults (Fig. 12). The basement is overlain by tertiary and quaternary sediments with a maximum of about 400 m thick. There are volcanic manifestations during the Tertiary. The basement consists in Palaeozoic crystalline rocks such as metamorphic rocks (schist, amphibolite, gneiss) and granites. In the SW part of the graben, the gravimetric data evidenced the occurrence of granites or gneiss rocks at depth. This area is still active and characterized by a significant seismic activity. The temperature measurements at 500 m depth show a geothermal anomaly parallel to the large-scale normal faults. The SW part of the graben is more interesting because there are some active faults evidenced by some gas anomalies (CO 2, He). The Strymon graben (Fig. 13) is located partly in Greece and partly in Bulgaria. This structure is oriented NW-SE and is located between the metamorphic rocks of the Rhodope in the NE and the Serbo-macedonian gneissic complex in the SW. The basin is a typical post-orogenic graben which is still active. The Strymon basin has experienced volcanic activity during the Tertiary. The total thickness of the Neogene sediments at the centre of the basin is estimated to be close to 4,000 m. A crosssection going through the Strymon 1 well (3,651 m) and the Strymon 2 well (2,678 m), shows that the depth of the basement is at about 3,7 km depth in the SW close to the fault and only 800 m in the NE part (Fig. 14). The deep seated geology is very variable at depth (micaschist, gneiss, granite, amphibolite) Meetings and exchanges During the reporting period, A. Genter attended a conference on May 2003, the European Geothermal Conference in Szeged (Hungary) (EGC2003). Several papers were published during the reporting period (see the references listed below). GGA- Hannover (R. Schellschmidt) provided us some temperature maps of Europe. Genter A., Guillou-Frottier L., Feybesse J.L., Nicol N., Dezayes C., Schwartz S. (2003) - Typology of potential Hot Fractured Rock resources in Europe, Geothermics, 32, p Genter A., Guillou-Frottier L., Feybesse J.L., Nicol N., Dezayes C., Schwartz S. (2003) - Typology of potential Hot Fractured Rock resources in Europe, EGC 2003, European Geothermal Conference, May 2003, Szeged, Hungary, 8 p., full length paper on CD-ROM. 24 BRGM/RP FR

26 Hot Dry Rock Energy project: Soultz-sous-Forêts PLANCHE 1 GEOLOGICAL MAP OF THE STRYMON GRABEN AREA 1 / 500,000 LEGEND lithology age sc scree, cone, fan GEOTECTONIC ZONES of NORTHERN GREECE indice JPB Holocene alluvium al Bulgaria gic olo Ge Albania m al lacustrine & continental clay, sand, conglomerate ap CENOZOIC FORMATIONS Macedonia Turkey ALPINE METAMORPHIC BASEMENT 27 km mq fluvio-lacustrine clay, sand, conglomerate Plio-Pleistocene cpq Lp basaltes Pliocene marine clay, sand, limestone, conglomerate mp lacustrine & continental clay, sand, limestone, conglomerate Middle Miocene to Early Pliocene marine clay, sand, limestone, conglomerate cn mn granite, granodiorite Aquitanain Ga acid to intermediate pyroclastites Eocene-Oligocene Ae Geotectonic unit possible Moho cq Pleistocene marine clay, sand, conglomerate West Thracian gneiss Rhodope complex metamorphic (WTGC) province Rhodope (RMP) metamorphic core complex (RMCC) Formation ElataiaSkalote lithology granite, migmatite indice JPB esg gneiss, schist, migmatite, marble, amphibolite, ultrabasite T Falacron marble, gneiss, schist F Pangaion gneiss, schist P granite, granodiorite veg Vertiscos Serbo-Macedonian gneiss complex (SMGC) gneiss, schist, amphibolite amphibolites, gabros, ultramafic rocks Kerdilion gneiss, marble, amphibolite K Cover conglomerate, sandstone, limestone, schist C Basement gneiss, schist, intrusives B Ophiolitic complex amphibolites, gabros, ultramafic rocks Circum Rhodope Belt Vardar (Axios) zone V Ophiolitic complex smo vo STRUCTURAL FEATURES geological contact Undifferenciated fault (dashed when infered) F 27 km Pleisto-Holocene normal fault (dashed when infered, F: foot wall) F Plio-Pleistocene normal fault (dashed when infered, F: foot wall) SM = Serbomacedonian Massif AB = Axios basin SB = Strymon basin Plio-Pleistocene strike-slip fault (dashed when infered) F SCHEMATIC CROSS-SECTION (located on the geological map) 1 : 100,000 Middle to Late Miocene normal fault (dashed when infered, F: foot wall) F Middle to Late Miocene sustractive exhumation thrust (dashed when infered, F: foot wall) Early Miocene strike-slip fault (dashed when infered) F Ante Neogene additive subduction thrust (dashed when infered, F: foot wall) Fig Geological map of the Strymon graben. BRGM/RP FR 25

27 Hot Dry Rock Energy project: Soultz-sous-Forêts PLANCHE 2 THEMATIC MAP OF THE STRYMON GRABEN AREA 1 / 500,000 LEGEND lithology STRYMON 1 WELL (Erki et al. 1984) age indice JPB sc scree, cone, fan Holocene alluvium al CENOZOIC FORMATIONS lacustrine & continental clay, sand, conglomerate 5000 cq Pleistocene mq marine clay, sand, conglomerate fluvio-lacustrine clay, sand, conglomerate Plio-Pleistocene cpq Lp basaltes Pliocene marine clay, sand, limestone, conglomerate mp lacustrine & continental clay, sand, limestone, conglomerate Middle Miocene to Early Pliocene marine clay, sand, limestone, conglomerate cn mn granite, granodiorite Aquitanain Ga acid to intermediate pyroclastites Eocene-Oligocene Ae Earthquakes Epicentres 178 C (linear extrapolation) (focal depths < 60 km) Magnitude STRYMON 2 WELL (Erki et al. 1984) SCHEMATIC DIAGRAM OF THE STRYMON GRABEN (out of scale) Time 5 to 5, to ,5 to 5, to ,0 to 6, to ,5 to 5, to ,0 to 8, to ,0 to 8,3 before 1900 South Vrondou fault South Kerkini fault South Menoikion fault North Angitis fault South Angitis fault Thermal Springs No data 38 to 39 C 41 to 44 C 49 C 56 C SW Strymon fault Mio-Pleistocene filling North Kerdylion fault 5000 East Kerdylion fault 150 C (linear extrapolation) Fig Thematic map of the Strymon graben. 26 BRGM/RP FR

28 2.3. WP11: STRATEGY FOR RESOURCE DEVELOPMENT OF EUROPEAN HDR/HFR SYSTEMS Participants: A. Genter, N. Lieutenant. Based on the maps done in the Pannonian basin in the framework of the WP10 (Genter et al., 2003), some estimations of the potential HFR/HDR resource area of central Europe have been done. In a first step, we considered all the hottest zones with a temperature higher than 200 C visible in the temperature map extrapolated at 5 km depth in Eastern Europe (Fig. 15b). As in Soultz, our goal in the Pannonian basin is to find hard rocks such as crystalline rocks and volcanic rocks in which we can development a HFR system. Then, in a second step, we tried to identify all the areas in the Pannonian which have basement rocks at 3 different levels of depth (2-3, 3-4, 4-5 km). By superimposition the hottest temperature zones and the map of the thickest sediments (Fig. 15c), we delineated the most promising zones for those two criteria (temperature, depth of the basement). In Hungary, there are about 15% of the area of this country which have a hottest temperature at depth and hard rock ranging between 2 and 3 km depth (Fig. 16). a) c) b) Fig a) Geographical map; b) Temperature extrapolated at 5 km depth; c) Location of the sediment thickness in the Pannonian basin. BRGM/RP FR 27

29 Fig Potential area for HFR resource in eastern Europe based on temperature maps for a hard rock accessible by drilling between 2 and 3 km depth. 28 BRGM/RP FR

30 3. Accompanying Scientific work The objective of the tasks performed in the framework of the accompanying scientific work during the last six months of the project is to improve the understanding of the hydraulic flow around and between the wells. The geochemical works carried out by BRGM between April and October 2003 have been mainly focalised on: - the last results obtained during the fluid monitoring from the GPK-3 well in March 2003; - the 1,6-nds and NaNO 3 tracer injection into GPK-3 between May and June 2003; - the fluid monitoring from the GPK-2 well between June 11 and July 9, GEOCHEMICAL MONITORING OF THE FLUID PRODUCED FROM THE GPK-3 WELL (MARCH 2003) As described in the previous report (Gentier, 2003), three injection tests were carried out into GPK-2 between January and March The complete fluid volume injected into this well was approximately 23,978 m 3. During each injection test, the 2,7- naphtalene disulfonate tracer (2,7-nds) was continuously injected at a constant concentration of about 3 mg/l into GPK-2. For this injection, a tracer solution of about 105 g/l was prepared in a tank of 1 m 3. During each injection test, some samples were collected into the tank and before the well head to control the concentrations of 2,7-nds and also, those of tracers injected in 2000 into GPK-2 (1,5-nds and Na-benzoate # 2 ppm). Results of these analyses performed by BRGM and EGI (Energy & Geoscience Institute at the University of Utah, USA) are reported in Table 6. The concentrations of Na-benzoate and 1,5-nds, before the well head, are very low and can be neglected in comparison to those of 2,7-nds. These low but far from zero values are a pollution due to the fact that the water injected in GPK-2 was for a part took from a water lagoon previously used to store water produced from GPK-2. Except for two samples, the concentrations of 2,7-nds for the fluid collected from the tank of 1 m 3 are close to the foreseen concentration of 105 g/l (Table 6). The very low values of 2,7-nds (< 4 µg/l; Table 6) correspond to those of the fluid injected into GPK-3 before mixing with the tracer. The scattered values of 2,7-nds around 3 mg/l (Table 6), observed for the fluid collected before well head, are probably caused by: - the inaccuracy due to the adjustment of the flow rate of the pump used to inject the tracer, relative to the variations of flow rate for the injected freshwater; - the location of the sampling point, where the mixing between tracer solution and injected fluid was not probably still very homogeneous. BRGM/RP FR 29

31 Fluid sample collected from tank Date 2,7-nds (BRGM) g/l GPK2-C1 23/01/ GPK2-C2 23/01/ GPK2-C3 23/01/ GPK2-C4 23/01/ GPK2-C5 23/01/ Fluid sample Date 1,5-nds (EGI) 1,5-nds (BRGM) 2,7-nds (EGI) 2,7-nds (BRGM) Na-benzoate collected at well head µg/l µg/l µg/l µg/l µg/l injected water 22/01/03 19: GPK2-HPI1 23/01/03 14:45 31 < GPK2-HPI2 24/01/03 09: GPK2-HPI3 25/01/03 09: GPK2-HPI4 26/01/03 09:10 47 < GPK2-HPI5 27/01/03 09: GPK2-HPI6 28/01/03 09: GPK2-HPI7 29/01/03 13: GPK2-HPI8 30/01/03 09:52 35 < GPK2-HPI9 13/02/03 09: GPK2-HPI10 14/02/03 16: GPK2-HPI11 15/02/03 09: GPK2-HPI12 16/02/03 09:00 72 < GPK2-HPI13 12/03/03 13: GPK2-HPI14 13/03/03 09: GPK2-HPI15 14/03/03 10: GPK2-HPI16 15/03/03 12:15 48 < Table 6 - Concentrations of 2,7-nds during its injection into the GPK-2 well in For mass balance calculations, it was decided to use a mean value of 3.06 mg/l. This value was calculated considering that, during the three injection tests, only about 0.7 m 3 of solution of 2,7-nds at 105 g/l were injected with 23,978 m 3 of freshwater into GPK-2. In March 2003, a volume of fluid of about 1,890 m 3 was discharged from GPK-3 using a flow rate of 4-5 l/s. A geochemical monitoring of this fluid was carried out by BRGM between March 12 and 18. Most of the results (parameters measured on site, concentrations of Cl, Ca, SO 4 and Br) and main conclusions were given in the previous report (Gentier, 2003). In this report, we will only present the data that were not previously available. The results concerning some cations such as Na, K, Mg and Li analysed in GPK-3 fluid samples are reported in Table 7, with the other analytical data. Relative accuracy is 5% for major cation analyses and 10% for Li determination. The results for the organic tracers (benzoate, 1,5-nds and 2,7-nds) analysed by High Pressure Liquid Chromatography (HPLC) in the BRGM laboratories are given and compared to the analytical results reported by EGI in Tables 7 and 8 and in Figure 17. These values are very close and their difference is usually smaller than their relative uncertainty (from 15 to 20%). In the previous report (Gentier, 2003), using the Cl, Ca and Br concentrations and the geochemical data obtained during the four production tests carried out in GPK-2 between December 2000 and April 2002 (Table 7), it was demonstrated that about 94-95% of geothermal brine and 5-6% of freshwater injected into GPK-2 were present in 30 BRGM/RP FR

32 the fluid discharged from GPK-3 at the end of the production test carried out in March 2003 (Table 7). Concentration (µg/l) ,5-nds data (fluid injected into GPK-2 in 2000) 2,7-nds data (fluid injected into GPK-2 in 2003) 15/03/03 00:00 16/03/03 00:00 17/03/03 00:00 18/03/03 00:00 19/03/03 00:00 Time (days) Blue triangles and red diamonds: BRGM data - Blue squares and red circles: EGI data. Fig Geochemical monitoring of the fluid discharged from the GPK-3 well (March 2003): analytical results of the organic tracers (1,5-nds and 2,7-nds). Fluid sample Date Na K Ca Mg Li Cl SO 4 Br Na-benz. 1,5-nds mg/l mg/l mg/kg mg/l mg/l mg/kg mg/l mg/l µg/l µg/l GPK3-03-P2SGC 15/03/ : GPK3-03-P4SGC 16/03/ : GPK3-03-P5SGC 16/03/ : GPK3-03-P8SPP 18/03/ : Fluid sample Na K Ca Mg Li Cl SO 4 Br Na-benz. 1,5-nds g/l g/l g/kg mg/l mg/l g/kg mg/l mg/l µg/l µg/l GPK-2 fluid composition before injection of freshwater in 2000 Freshwater injected in GPK-2 fluid composition 18/03/ estimated for March 18, 2003 Table 7 - Geochemical monitoring of the fluid discharged from the GPK-3 well (march 2003): results of some chemical analyses compared to estimated data. Among these 5-6% of freshwater, the concentrations of 1,5-nds and 2,7-nds measured by BRGM indicated that the fluid discharged from GPK-3 was constituted by 4-5% of freshwater injected into GPK-2 in 2000 and about 1-2% of freshwater injected into GPK-2 in Taking into account the analytical uncertainties, the organic tracer data were in very good agreement with Cl, Ca and Br data. All these data suggested the existence of an hydraulic connection between GPK-2 and GPK-3 before any stimulation of GPK-3. They confirmed the internal convection BRGM/RP FR 31

33 evidenced from the monitoring of the previous production tests carried out in GPK-2 and the value estimated for the flow rate of the deep fluid ( m 3 /h). They also allowed to showing that the 1,5-nds tracer had a conservative behaviour at least during a period of almost 3 years at temperature close to 200 C. The new data confirm and validate these conclusions. In particular, the concentrations of Na, K, Mg and Li analyzed in the fluid sample collected from GPK-3 well on March 18, 2003, are in good agreement with the presence of about 5-6% of freshwater previously injected into GPK-2 (see comparison between analytical and foreseen data in Table 7). The results obtained for the 1,5-nds and 2,7-nds tracers, mentioned in the previous report (Gentier, 2003), are now validated by BRGM and EGI. The Figures 17 and 18 and the Table 8 illustrate how the freshwater injected in 2000 into GPK-2 (represented by 1,5-nds) is progressively replaced by the freshwater injected in 2003 into this same well (represented by 2,7-nds) between March 14 and 18, Estimated % of freshwater in total discharged fluid Maximum total freshwater injected into GPK-2 (from Cl data) Freshwater injected into GPK-2 in 2003 (estimated from 2,7-nds data) Freshwater injected into GPK-2 in 2000 (estimated from1,5-nds data) 15/03/03 00:00 16/03/03 00:00 17/03/03 00:00 18/03/03 00:00 19/03/03 00:00 Time (days) Blue triangles and red diamonds: BRGM data - Blue squares and red circles: EGI data. Fig Estimation of the proportions of freshwater injected into GPK-2 in 2000 and 2003, relative to the total mass of fluid discharged from the GPK-3 well (March 2003), using the concentrations of Cl and organic tracers (1,5 and 2,7-nds). During this period, the contribution of freshwater injected in 2000 decreases approximately from 5.0 to 4.0% whereas that of freshwater injected in 2003 increases from 0.9 to 1.6%. The whole of freshwater slightly decreases from 5.9 to 5.6%. At the beginning of this production test, freshwater is constituted of about 87% of freshwater injected in 2000 and 13% of freshwater injected in At the end of this test, the respective proportions are around 70 and 30%. The amount of freshwater injected between January and March 2003 into GPK-2, which has been recovered in GPK-3, after a production of 1,890 m 3 of fluid, can 32 BRGM/RP FR

34 be estimated to 32 m 3, which represents 0.13% of the total volume of freshwater injected into GPK-2 (23,978 m 3 ). Fluid sample Date Cl Br Na-benz. 1,5-nds (BRGM) 1,5-nds (EGI) 2,7-nds (BRGM) 2,7-nds (EGI) mg/kg mg/l µg/l µg/l µg/l µg/l µg/l GPK3-03-P1SGC 14/03/03 17: < < GPK3-03-P2SGC 15/03/03 10: GPK3-03-P3SGC 15/03/03 14: GPK3-03-P4SGC 16/03/03 09: GPK3-03-P5SGC 16/03/03 19: GPK3-03-P5SPP 16/03/03 19: GPK3-03-P6SGC 17/03/03 08: GPK3-03-P7SPP 17/03/03 19: GPK3-03-P8SPP 18/03/03 08: GPK3-03-P9SPP 18/03/03 19: Fluid sample Date % FW % FW % FW 2000 % FW 2000 % FW 2003 % FW 2003 Cl Br 1,5-nds (BRGM) 1,5-nds (EGI) 2,7-nds (BRGM) 2,7-nds (EGI) GPK3-03-P1SGC 14/03/03 17: GPK3-03-P2SGC 15/03/03 10: GPK3-03-P3SGC 15/03/03 14: GPK3-03-P4SGC 16/03/03 09: GPK3-03-P5SGC 16/03/03 19: GPK3-03-P5SPP 16/03/03 19: GPK3-03-P6SGC 17/03/03 08: GPK3-03-P7SPP 17/03/03 19: GPK3-03-P8SPP 18/03/03 08: GPK3-03-P9SPP 18/03/03 19: Table 8 - Geochemical monitoring of the fluid discharged from the GPK-3 well (March 2003): analytical results of the organic tracers and estimation of the proportions of freshwater injected into GPK-2 in 2000 and 2003 relative to the total mass of fluid discharged from GPK-3, using the concentrations of Cl, Br and organic tracers (1,5-nds and 2,7-nds) INJECTION OF THE 1,6-NDS AND NaNO 3 TRACERS INTO GPK-3 (MAY - JUNE 2003) Two injection tests were carried out into GPK-3 between May and July The fluid volume injected during the first test (May 27-June 6) was about 34,000 m 3 using flow rates l/s. During the second test (June 24-July 11), this volume was 25,305 m 3 using flow rates of l/s. The complete fluid volume injected into GPK-3 was 59,305 m 3. In the first injection test, only freshwater ( Etang water) was injected into GPK-3. In the second test, a mixing constituted of an high proportion of fluid produced by GPK-2 and a low amount of freshwater was injected. A short injection of 3,300 m 3 of fluid with a solution of 2,7-nds tracer was also performed into GPK-2 on June 3-5 (Table 9) Injection of 1,6-nds During each injection test, the 1,6-naphtalene disulfonate (1,6-nds) tracer was continuously injected at a constant concentration into GPK-3. This concentration was fixed to 3 mg/l of fresh water. For this tracer injection, 100 kg of pure 1,6-nds were dissolved in 1,000 l of freshwater by BRGM using a tank of 1 m 3 in order to prepare a tracer solution of about 100 g/l. As this volume of tracer solution was not sufficient, 75 kg of pure 1,6-nds were additionally dissolved in 750 l of freshwater in the same tank. BRGM/RP FR 33

35 Fluid sample Date 1,5-nds (BRGM) 1,5-nds (EGI) 2,7-nds (BRGM) 2,7-nds (EGI) 1,6-nds (BRGM) 1,6-nds (EGI) Injection of 2,7-nds into GPK-2 mg/l mg/l mg/l mg/l mg/l mg/l GPK2-INJ1 03/06/03 09:00 < 0.5 n.a n.a. < 0.5 n.a. Fluid sample Date Na-benzoate 1,5-nds (BRGM) 1,5-nds (EGI) 2,7-nds (BRGM) 2,7-nds (EGI) 1,6-nds (BRGM) 1,6-nds (EGI) Injection of 1,6-nds into GPK-3 mg/l mg/l mg/l mg/l mg/l mg/l mg/l Etang < n.a n.a n.a. GPK3-INJ-BP1 27/05/03 17:32 n.a. < 0.5 n.a. < 0.5 n.a n.a. GPK3-INJ1 27/05/03 09:00 n.a. n.a. 0 n.a n.a GPK3-INJ2 28/05/03 09:00 n.a. < < GPK3-INJ3 29/05/03 09:00 n.a. < < GPK3-INJ4 30/05/03 09:00 < 0.02 < < GPK3-INJ5 31/05/03 09:00 n.a. < < GPK3-INJ6 01/06/03 09:00 n.a. < < GPK3-INJ7 02/06/03 09:00 n.a. < < GPK3-INJ8 03/06/03 09:00 n.a. < < GPK3-INJ9 04/06/03 09:00 n.a. < < GPK3-INJ10 05/06/03 09:00 n.a. < < GPK3-INJ11 06/06/03 09:00 n.a. < < GPK3-INJ13 24/06/03 22:00 n.a. < GPK3-INJ14 25/06/03 09:00 n.a. < GPK3-INJ15 25/06/03 21:00 n.a. < GPK3-INJ16 26/06/03 09:00 n.a. < GPK3-INJ17 26/06/03 21:00 n.a. < GPK3-INJ18 27/06/03 09:00 n.a. < GPK3-INJ19 27/06/03 21:00 n.a. < GPK3-INJ20 28/06/03 09:00 n.a. < GPK3-INJ21 28/06/03 21:00 n.a. < GPK3-INJ22 29/06/03 09:00 n.a. < GPK3-INJ23 29/06/03 21:00 n.a. < GPK3-INJ24 30/06/03 21:00 n.a. < GPK3-INJ26 01/07/03 09:00 n.a. < GPK3-INJ27 01/07/03 21:00 n.a. < < GPK3-INJ28 02/07/03 09:00 n.a. < GPK3-INJ29 02/07/03 21:00 n.a. < GPK3-INJ30 03/07/03 09:00 n.a. < GPK3-INJ31 03/07/03 21:00 n.a. < GPK3-INJ32 04/07/03 09:00 n.a. < GPK3-INJ33 04/07/03 21:00 n.a. < GPK3-INJ34 05/07/03 09:00 n.a. < GPK3-INJ35 05/07/03 21:00 n.a. n.a n.a n.a GPK3-INJ36 06/07/03 09:00 n.a. < GPK3-INJ37 06/07/03 21:00 n.a. < GPK3-INJ38 07/07/03 09:00 n.a. < GPK3-INJ39 07/07/03 21:00 n.a. < GPK3-INJ40 08/07/03 09:00 n.a. < GPK3-INJ41 08/07/03 21:00 n.a. n.a n.a n.a GPK3-INJ42 09/07/03 21:00 < 0.01 < n.a. : not analysed. Table 9 - Tracer concentrations in the fluid injected into GPK-2 (June 3-5, 2003) and into GPK-3 (from 27/05 to 9/07/2003). This solution was mixed to the fluid injected into GPK-3 with a pump whose the flow rate was permanently adapted to that of the injected fluid in order to have the fixed concentration of about 3 mg/l. During each injection test, some samples were collected before the well head to control the concentration of 1,6-nds in the fluid injected into GPK-3 and also, those of other tracers (Na-benzoate, 1,5-nds and 2,7-nds). Results of these analyses performed by BRGM and EGI are reported in Table 9. The concentrations of Na-benzoate and 1,5-nds, before the well head, are always very low and can be neglected in comparison to those of 1,6-nds. The concentrations of 2,7- nds are also very low when only freshwater is injected into GPK-3 (Table 9). They become significant in the second injection test, after using of the fluid produced from GPK-2. During the first injection test, the scattered values of 1,6-nds between 1 and 3 mg/l, observed for the fluid collected before the head of GPK-3 (Table 9), are probably caused by the same phenomena as those described for the injection of 2,7-nds 34 BRGM/RP FR

36 (inaccurate adjustment of the flow rate of the pump used to inject the tracer, relative to the variations of flow rate for the injected freshwater; bad homogeneity of the fluid at the sampling point). For mass balance calculations, it was decided to use a mean value of about 2.79 mg/l for the fixed concentration. This concentration was calculated considering that, during the first injection test, about 0.95 m 3 of solution of 1,6-nds at 100 g/l were injected with 34,000 m 3 of freshwater into GPK-3. Fluid sample Date Density ph Cond. (25 C) Cl Cl Ca Ca SiO 2 Alk. Tracers Cations Anions Comments ms/cm mg/l mg/kg mg/l mg/kg mg/l meq/l GPK2-P1 11/06/03 21: X X X GPK2-P2 12/06/03 09: X X X GPK2-P3 12/06/03 21: X X X GPK2-P4 13/06/03 09: X X X GPK2-P5 13/06/03 21: X X X GPK2-P6 14/06/03 09: X X X GPK2-P7 14/06/03 21: X X X GPK2-P8 15/06/03 09: X X X GPK2-P9 15/06/03 21: X X X GPK2-P10 16/06/03 09: X X X GPK2-P11 16/06/03 21: X X X GPK2-P12 24/06/03 17: X X X new injection into GPK-3 and production from GPK-2 on 24/06/03 at 15h00 GPK2-P13 25/06/03 08: X X X GPK2-P14 25/06/03 18: X X X fluid collected after degassing (out of the big pipe) because the sampling point was stopped GPK2-P15 26/06/03 08: X X X injection of 250 kg NaNO 3 GPK2-P16 26/06/03 22: X X X GPK2-P17 27/06/03 08: X X X GPK2-P18 27/06/03 09: X X X GPK2-P19 27/06/03 21: X X X GPK2-P20 28/06/03 09: X X X GPK2-P21 28/06/03 21: X X X GPK2-P22 29/06/03 09: X X X GPK2-P23 29/06/03 21: X X X GPK2-P24 30/06/03 09: X X X 30/06/03 16: X GPK2-P25 30/06/03 21: X X X GPK2-P26 01/07/03 09: X X X 01/07/03 16: Attention : for Si analyses, volume dilution performed at 75 C GPK2-P27 01/07/03 21: X X X 02/07/03 08: /07/03 17: GPK2-P28 02/07/03 21: X X X 03/07/03 08: GPK2-P29 03/07/03 21: X X X GPK2-P30 04/07/03 09: X X X GPK2-P31 04/07/03 21: X X X GPK2-P32 05/07/03 09: X X X GPK2-P33 05/07/03 21: X X X GPK2-P34 06/07/03 09: X X X GPK2-P35 06/07/03 21: X X X GPK2-P36 07/07/03 09: X X X 07/07/03 10: GPK2-P37 07/07/03 21: X X X GPK2-P38 08/07/03 09: X X X 08/07/03 10: GPK2-P39 08/07/03 21: X X X 09/07/03 08: GPK2-P40 09/07/03 09: X X X GPK2-P41 09/07/03 21: X X X GPK2-P42 09/07/03 23: X X X Table 10 - Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): on site measurements. During the second injection test, most of the values of 1,6-nds in the fluid samples collected before the head of GPK-3 are higher at the beginning, then lower during the last three days than 3 mg/l (Table 9). The high values can be explained by the two same processes as those previously described but also by the use of the fluid produced from GPK-2 for injection into GPK-3. Indeed, this fluid already contains some 1,6-nds tracer (see Table 15), which is then added to the fixed concentration of about 3 mg/l. The low values were intentional due to the little proportion of fresh water in the injected fluid (mostly produced from GPK-2). BRGM/RP FR 35

37 A mean estimation of the fixed concentration can be calculated to 3.16 mg/l, considering that, during the second injection test, about 0.80 m 3 of solution of 1,6-nds at 100 g/l were injected with 25,305 m 3 of fluid into GPK-3. The concentration of 1,6- nds, daily analysed in the fluid produced from GPK-2 (see Table 15) and used for injection into GPK-3, must be also added to this value. Consequently, the concentrations of 1,6-nds in the fluid initially injected into GPK-3 vary from = 3.58 mg/l to = 4.03 mg/l during the second injection test, between June 24 and July 9, Some particularly low analysed values of 1,6-nds (< 1 mg/l; Table 9), especially at the end of this test, probably correspond to the absence of mixing between tracer solution and fluid injected into GPK Injection of NaNO 3 This tracer was injected into GPK-3 to the request of GEIE whereas GPK-2 was producing. A solution of about 245 g/l was prepared on June 25 by dissolving 250 kg of 98% pure NaNO 3 in 1 m 3 of freshwater. A volume of 0.95 m 3 of this solution mixed to 33,41 m 3 of fluid was injected into GPK-3 on June 26, between 14h04 and 14h28. For this mixing, a pump whose the flow rate was adapted to that of the injected fluid (23.2 l/s) was used in order to have a constant NaNO 3 concentration of 6.8 g/l (0.95 x 245 / 34.36) GEOCHEMICAL MONITORING OF THE FLUID PRODUCED FROM THE GPK-2 WELL (JUNE - JULY 2003) Two production tests were carried out from GPK-2 between June 11 and 16, and June 24 and July 9, During the first test, a volume of fluid of about 4,030 m 3 was discharged from GPK-2 using flow rates of about l/s. A volume of 22,456 m 3 was produced in the second test with flow rates of l/s. A geochemical monitoring of this fluid was performed by BRGM during these two tests. The values of the parameters measured on site such as temperature, conductivity, ph, Eh, alkalinity and concentrations of dissolved chloride, calcium and silica, are reported in Table 10. Relative precision is 5% for most of these analyses. Nitrate analyses were performed: - on site using a colorimetric method (Merck kit); - in the BRGM laboratory using Ionic Chromatography (IC). Precision for both methods is about 5%. Results are reported in Table 11. The data obtained using the IC technique indicate that the nitrate tracer was not detected in the fluid discharged from GPK-2. However, these results are very different from those analyzed by colorimetry, which show relatively high nitrate concentrations between July 3 and 8, at the end of the production test (Table 11; Fig. 9). 36 BRGM/RP FR

38 n.a. : not analysed. Table 11 - Geochemical monitoring of the fluid discharged from GPK-2 (from 26/06 to 9/07/2003): NO 3 analysed by colorimetry on site and by Ionic Chromatography (IC) at BRGM laboratory. BRGM/RP FR 37

39 Normally, the colorimetric method cannot be quantitatively applied on saline fluids such as those produced from GPK-2 because of the existence of ion interference. This technique was only used in this study to be able to qualitatively detect nitrate ions on site. Tests carried out in the BRGM laboratory have shown that the NO 3 signal is hardly reduced in an high chloride solution (Tables 12, 13 and 14). Ionic Chromatography is the recommended technique and had to confirm and quantify the presence of nitrate ions detected on site. Time NO 3 analysed by Ionic Chromatography (IC) mg/l NO 3 analysed by colorimetry (Nova 60) mg/l 0 h h h h (1,8 diluted 2 times) 100 h days 20.8 Table 12 - Analytical results obtained on a fluid sample collected from GPK-2 with addition of a NO 3 solution in order to have a NO 3 concentration of 25 mg/l in this sample. Water sample NO 3 analysis using Nova 60 mg/l NO 3 analysis using Milton Roy mg/l water standard: 6,7 mg NO 3 /l water standard: 10 mg NO 3 /l 8.4 standard for calibration water standard: 20 mg NO 3 /l 18.4 standard for calibration water standard: 25 mg NO 3 /l 25.2 n.a. solution GPK-2: 25 mg NO 3 /l - 67h 4.0 < 2 solution GPK-2: 25 mg NO 3 /l - 67h (1/2) 1.8 n.a. solution GPK-2: 25 mg NO 3 /l just before analysis 3.1 n.a. GPK-2 sample 28/6-16h (< 1 mg NO 3 /l on site) * < 2 < 2 GPK-2 sample 6/7-4h (20 mg NO 3 /l on site) * < 2 < 2 GPK-2 sample 6/7-12h (24 mg NO 3 /l on site) * < 2 < 2 n.a. : not analysed. solution GPK-2 : a NO 3 solution has been added in a fluid sample collected from GPK-2 in order to have a NO 3 concentration of 25 mg/l in this sample. * : < 2.5 mg NO 3 /l when analysed by Ionic Chromatography. Table 13 - Analytical results of nitrate obtained using the colorimetric technique. However, in this particular case, it is extremely probable that the high concentrations of nitrate analyzed on site by colorimetry between July 3 and 8 are really related to the injection of NaNO 3 into GPK-3. In reduced medium such as that of the fluid produced from GPK-2, the nitrate ions may have been transformed in nitrite ions, which would have been then the ions detected by colorimetry. Indeed, tests performed in the BRGM laboratory have shown these ions can strongly interfere with nitrate ions using this technique (Table 14). The fact that the nitrite ions are lowly stable as a function of time and that their chromatographic peak is very close to that of the chloride ions could explain why they have not been detected by IC in the high Cl fluid produced from GPK BRGM/RP FR

40 Water sample NO 3 analysis NO 3 analysis NO 3 analysis using Merck using Milton Roy using HP8452 mg/l mg/l mg/l 09/09/03 analysis water standard : 10 mg NO 3 /l GPK-2 sample analysis (09/09/03) GPK-2 sample 6/7 diluted with 2/3 water 5.2 < GPK-2 sample 6/7 diluted with 1/10 water 3.3 < GPK-2 sample 6/7 diluted 2/3: 33 mg NO 3 /l GPK-2 sample 6/7 diluted 2/3: 33 mg NO 2 /l GPK-2 sample 6/7 diluted 2/3: 33 mg NH 4 /l < 2 < /09/03 analysis blanck reagent 0.7 1,3 3.7 water standard: 10 mg NO 3 /l (09/09/03) water standard: 33 mg NO 3 /l (09/09/03) water standard: 50 mg NO 3 /l (09/09/03) n.a. water standard: 50 mg NO 2 /l (0,1 g NO 2 /l) GPK-2 sample analysis (10/09/03) GPK-2 sample 7/7 diluted with 2/3 water 5.3 < GPK-2 sample 7/7 diluted with 1/3 water 2 < GPK-2 sample 7/7 diluted 2/3: 33 mg NO 3 /l GPK-2 sample 7/7 diluted 2/3: 33 mg NO 2 /l GPK-2 sample 7/7 diluted 2/3: 50 mg NO 2 /l A NO 3, NO 2 or NH 4 solution has been added in the fluid sample collected from GPK-2 in order to have a NO 3, NO 2 or NH 4 concentration of 33 or 50 mg/l in this sample. n.a. : not analysed. Table 14 - Analytical results of nitrate obtained using the colorimetric technique. Assuming that the signal observed by colorimetry in the fluid produced from GPK-2 between July 3 and 8 (Fig. 19) is related to the injection of NaNO 3 into GPK-3 done on June 26, it can be then deduced that only 7.25 days have been necessary to this tracer to go from GPK-3 to GPK-2. Maximum of signal was detected between 8 and 11 days after the NaNO 3 injection (Fig. 19). These results are similar to those obtained in 1997 for the tracer tests carried out between GPK-1 and GPK-2 for which the tracers injected into GPK-1 were detected in the GPK-2 fluid 3 to 6 days after their injection and maximum of tracers was observed between 6 and 10 days after this injection (Vaute et al., 1998). The time of circulation, slightly higher from GPK-3 to GPK-2 than from GPK-1 to GPK- 2, can be explained by the distance between well : the distance between GPK-2 and GPK-3 is about 650 m whereas that between GPK-1 and GPK-2 is only 450 m. A mean value of circulation fluid rate between GPK-3 and GPK-2 has been estimated to: 650 / 7.25 x 24 = 3.73 m/h. Given the qualitative nature of the colorimetric NaNO 3 analyses, the amount of tracer recovered in the fluid discharged from GPK-2 cannot be calculated. The results for the organic tracers (1,5-nds, Na-benzoate, 2,7-nds and 1,6-nds) analyzed by HPLC in the BRGM laboratories are given and compared to the analytical results reported by EGI in Table 15 and in Figures 20, 21 and 23. These values are very close and their difference is usually smaller than their relative uncertainty (from 15 to 20%). BRGM/RP FR 39

41 40.0 NaNO 3 concentration (mg/l) /06/03 28/06/03 30/06/03 02/07/03 04/07/03 06/07/03 08/07/03 10/07/03 Time (days) Colorimetric analyses Fig Geochemical monitoring of the fluid discharged from the GPK-2 well (from 26/06 to 9/07/2003): analytical results of the NaNO 3 tracer obtained using the colorimetric technique on site. The results concerning the 1,6-nds tracer seem to be rather in agreement with those found for nitrate (Table 15). Indeed, the concentrations of 1,6-nds are already relatively high in the fluid discharged from GPK-2, after only 15 days of the injection of this tracer into GPK-3. A contribution of freshwater injected into GPK-3 of about 10-11% of the total mass of fluid produced from GPK-2 can be already estimated at the beginning of the first production test (Table 15). During this first test, the chloride concentrations indicate an increasing contribution of geothermal brine from about 37 to 50% (Table 15). This increase is mainly due to the partial discharge of the m 3 of 2,7-nds traced freshwater injected into GPK-2 on June 3-5. As the concentration of 2,7-nds is badly known during the injection of this freshwater into GPK-2 (Table 9), it is difficult to do a mass balance using this tracer, at the beginning of this production test. At the end of the first production test, the concentrations of the four tracers analysed in the fluid discharged from GPK-2 (Table 15 and Figs. 20, 21 and 23) indicate a contribution of about: - 4-5% of freshwater injected into GPK-2 in 2000 (estimated using 1,5-nds; Table 15). The concentrations of Na-benzoate show a slightly higher proportion (6-7%). These differences can be attributed to analytical uncertainties but also to a low background of this tracer, which was injected in 1997 into GPK-1; 40 BRGM/RP FR

42 Table 15 - Geochemical monitoring of the fluid discharged from the GPK-2 well (from 11/06 to 9/07/2003): tracer analyses and estimation of the proportions of fluid injected into GPK-2 and into GPK-3 relative to the total mass of fluid discharged from GPK-2, using the concentrations of Cl and organic tracers. BRGM/RP FR 41