ELEMENTS GOVERNING THE RATIO HYDRAULIC PERFORMANCES/INDUCED MICROSEISMIC NUISANCES DURING THE STIMULATION OF 3EGS SOULTZ TYPE » RESERVOIRS A.Gérard GEIE « EMC » N.Cuenot GEIE « EMC » J.Charlety EOST C.Dorbarth EOST L.Dorbath EOST S.Gentier BRGM H.Haessler EOST
ELEMENTS GOVERNING THE RATIO HYDRAULIC PERFORMANCES/INDUCED MICROSEISMIC NUISANCES DURING THE STIMULATION OF « EGS SOULTZ TYPE » RESERVOIRS � Basic Basic available available informations informations today today: : � � What What we we know know about about the the structure structure of of the the natural natural � medium (geothermal geothermal reservoir reservoir) ) around around the the wells wells medium ( � The The main main results results of of previous previous stimulation tests stimulation tests already already � performed at at - -4000m/ 4000m/- -5000m 5000m at at Soultz Soultz performed � Basic questions to Basic questions to day day: : � � What What seems seems to to limitate limitate the the efficiency efficiency of of hydraulic hydraulic � stimulations at at - -4000m/ 4000m/- -5000m 5000m already already performed performed at at stimulations Soultz? ? Soultz � What could be What could be the key the key parameters parameters favourizing favourizing or or � limiting the the pressure pressure waves waves propagation (i.e. propagation (i.e. limiting microsismicity propagation in a propagation in a natural natural geothermal geothermal microsismicity system of of Soultz Soultz type? type? system
ELEMENTS GOVERNING THE RATIO HYDRAULIC PERFORMANCES/INDUCED MICROSEISMIC NUISANCES DURING THE STIMULATION OF « EGS SOULTZ TYPE » RESERVOIRS � The The previous questions rise other questions previous questions rise other questions : � : � Is it likely that there is any systematic exploitable Is it likely that there is any systematic exploitable � link between the pressure waves propagation pressure waves propagation link between the main water flows between the wells and and the main water flows between the wells and and the far field in the natural geothermal towards the far field in the natural geothermal towards the reservoir at Soultz Soultz? ? reservoir at � Some today available experimental results are Some today available experimental results are � suggesting that the answer to that question is far to suggesting that the answer to that question is far to be obviously always yes. be obviously always yes. � What could be the guide lines towards an What could be the guide lines towards an � experimental approach aiming at the experimental approach aiming at the improvement of stimulations efficiency (ie ie improvement of stimulations efficiency ( better hydraulic results for lower costs and better hydraulic results for lower costs and nuisances) at Soultz Soultz? ? nuisances) at
The medium: medium: Main Main hydrothermally hydrothermally The active structures making making the the natural natural active structures geothermal reservoir reservoir at at Soultz Soultz geothermal Document Yves GERAUD
The medium: medium: A A general general conceptual conceptual The model of of the the geothermal geothermal reservoir reservoir model at Soultz Soultz at
Hydraulic stimulations stimulations of of GPK2, GPK2, Hydraulic GPK3, GPK4: Induced GPK3, GPK4: Induced microseismicity microseismicity � Blue: Blue: Microseismicity Microseismicity during GPK3 during GPK3 � stimulation: stimulation: � Maximum injected volume and flows; Maximum injected volume and flows; � Largest cloud, largest nuisance Largest cloud, largest nuisance • Injectivity • Injectivity before: 3l/s/MPa before: 3l/s/MPa GPK2 • Injectivity Injectivity after: 3l/s/MPa after: 3l/s/MPa • � Green: Green: Microseismicity Microseismicity during GPK2 during GPK2 � stimulation: stimulation: � Medium injected volume and flows; Medium injected volume and flows; GPK3 � 1 km Medium cloud, medium nuisance Medium cloud, medium nuisance • Injectivity • Injectivity before: 0.2l/s/MPa before: 0.2l/s/MPa • Injectivity Injectivity after: 4l/s/MPa after: 4l/s/MPa • � Red: Red: Microseismicity Microseismicity during GPK4 during GPK4 � GPK4 stimulation: stimulation: � Minimum injected volume and flows; Minimum injected volume and flows; � minimum cloud, minimum nuisance minimum cloud, minimum nuisance • Injectivity Injectivity before: 0.2l/s/MPa before: 0.2l/s/MPa • • Injectivity • Injectivity after: 2l/s/MPa after: 2l/s/MPa
Spatial and and magnitude distributions magnitude distributions of of Spatial the microseismic microseismic events events at at Soultz Soultz the Gutenberg-Richter distributions GPK2 : 2000 10 GPK3 25 000m 3 :2003 37 000m 3 GPK3 GPK4 :2004 Limite de 9 000m 3 1 sensibilité humaine GPK4 :2005 12 000m 3 0.1 0.01
Basic features features governing governing microseismic microseismic Basic events distribution distribution at at Soultz Soultz events
Some observations observations Some During the massive hydraulic stimulation � During the massive hydraulic stimulation � of GPK2 the « « microseismic microseismic cloud cloud » » of GPK2 the extended mostly northward and was not extended mostly northward and was not covering the location of GPK3 open hole: covering the location of GPK3 open hole: Nevertheless the hydraulic conection conection GPK2 GPK2- - Nevertheless the hydraulic � � GPK3 was observed while drilling GPK3 GPK3 was observed while drilling GPK3 (Tracer return) and confirmed as being (Tracer return) and confirmed as being major before any stimulation of GPK3 major before any stimulation of GPK3 Open Hole Thermic traces of near traces of near wellbore wellbore storages storages � Thermic � GPK3 can be observed can be observed Overpressurized volumes can be observed volumes can be observed � � Overpressurized close from drained zones close from drained zones
Storage zone in GPK4 zone in GPK4 Storage 4000 temperatures observed At equilibium before during circulation Temperature at equilibium stimulation temperatures 4200 before stimulation were:~183°C at casing shoe Temperature at equilibium Logging depth (meters) after circulation 4400 and 191°C at 5000m (Logging depth) 4600 Casing shoe Temperatures observed 4800 during production: Storage 5000 zone?? 5200 ~172° at casing shoe 150 155 160 165 170 175 180 185 190 195 200 Temperature (°C) ~180°C at ~5000m After 5.5 months of production and total of 35000 m3 produced: Only 7000m3 of fresh injected water recovered The produced flow contained ~85% of natural geothermal brine In the storage zone the temperature was still ~15°C lower than at equilibrium
Microseismicity generated under generated under Microseismicity GPK2 by over pressures in GPK3 GPK2 by over pressures in GPK3 Main results December 2005: GPK2 : Closed loop circulation test: Microseismicity: July to November 2005 Downhole under pressure : ~ - 1.3MPa Depth GPK3 : Downhole over pressure : ~ + 4.5 to 6 MPa GPK4 : Downhole under pressure : GPK3 GPK2 Depth GPK4 ~ - 1MPa
Main conclusions Main conclusions In a complex natural geothermal In a complex natural geothermal reservoir of Soultz Soultz type: type: reservoir of Massive hydraulic stimulation techniques will generate a - Massive hydraulic stimulation techniques will generate a - large microseismic microseismic activity in the far field activity in the far field which can be large which can be considered as a problematic nuisance. considered as a problematic nuisance. - There is no demonstrated link There is no demonstrated link between the improvement of the between the improvement of the - wells hydraulic performances and this far field microseismic microseismic wells hydraulic performances and this far field activity . activity . - Nevertheless hydraulic stimulation at Soultz Nevertheless hydraulic stimulation at Soultz- -5000m 5000m- - seemed seemed - sometimes to show a limited efficiency (Mostly at rather short sometimes to show a limited efficiency (Mostly at rather short distance from the wells for the improvement of their connexions connexions to large to large distance from the wells for the improvement of their natural drains which could exist in the vicinity?) . natural drains which could exist in the vicinity?) . - What could be the investigations and/or tests What could be the investigations and/or tests which will be which will be - useful (or necessary) for getting rapidly similar ( or better ) ) useful (or necessary) for getting rapidly similar ( results with much less nuisances in Soultz Soultz type EGS projects. type EGS projects. results with much less nuisances in
What could be the future What could be the future techniques being both more techniques being both more efficient than up to now and limiting efficient than up to now and limiting the microseismic microseismic nuisances during nuisances during the EGS operations ? EGS operations ? � Injections of little volumes at high flow Injections of little volumes at high flow � rates? (followed by production?) rates? (followed by production?) � Chemical stimulations? Chemical stimulations? � � Combination of both? (Acid Combination of both? (Acid frac frac ?) ?) � � Others? Others? �
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