The Experts below are selected from a list of 1710 Experts worldwide ranked by ideXlab platform
Michel Frogneux - One of the best experts on this subject based on the ideXlab platform.
-
Injection tests at the EGS reservoir of Soultz-sous-Forêts. Seismic response of the GPK4 stimulations
Geothermics, 2014Co-Authors: Marco Calò, Catherine Dorbath, Michel FrogneuxAbstract:Abstract The European Enhanced Geothermal System (EGS) program of Soultz-sous-Forets is organized around three wells (GPK2, GPK3, and GPK4) drilled to a depth of about 5000 m. Hydraulic stimulations were performed in order to increase the injectivity of the reservoir and the connectivity among the wells. The stimulation of GPK4 was carried out in two stages, in September 2004 and in February 2005, followed by an acidification test performed in March 2005. The stimulations produced fewer induced events than those of the other wells, with interpretation remaining difficult. In this work we present some new observations on the seismicity of the GPK4 stimulations after a complete review of the seismic bulletins collected in 2004 and 2005. Furthermore, the events were relocated using the double difference method. The new images of the seismicity are presented in temporal sequences according to the main variations of the injection parameters. The seismic events that occurred during the 2004 stimulation are grouped in a dense cloud and centered on the well Open-Hole Section, while in 2005 seismicity depicts a specific pattern suggesting that the “natural” stress field in the reservoir was not completely restored. Finally, the events recorded during the acidified test show that the reservoir behaved differently from the previous injections, which suggests that a different mechanism has controlled the induced seismicity.
Mian Chen - One of the best experts on this subject based on the ideXlab platform.
-
investigation on acid fracturing treatment in limestone formation based on true tri axial experiment
Fuel, 2019Co-Authors: Ruxin Zhang, Mian ChenAbstract:Abstract Acid fracturing treatment is the most effective method for stimulating limestone formations, which are abundant in the northeast Sichuan basin of China. The effective acid etching improves the fracture width, resulting in high fracture conductivity, while fracture propagation behavior is always affected by discontinuities and the fractured vuggy structure. Hence, the fracture geometry differs from that in homogeneous formations. However, the fracture propagation mechanism remains unclear. In order to understand the process more clearly, a series of large-scale, true tri-axial simulation experiments were conducted for the first time to investigate the fracture initiation and propagation in limestone formations under acid fracturing treatment. Moreover, the effects of multiple factors on fracture propagation were discussed, and a 3D scanner was used to depict and describe the fracture surface etching feature. The experimental results demonstrated that natural fractures had a serious impact on the fracture initiation and propagation. The induced fracture initiated from the Open-Hole Section to form a transverse fracture, or from the natural fractures to form a longitudinal or an inclined fracture. The fracture surface was rougher in the acid fracturing than in hydraulic fracturing, owing to the non-uniform acid fluid dissolution. The black-brown remains on the fracture surface were the result of acid etching, which could be used to judge the fracture propagation direction and area. However, the roughness degree of the fracture surface near the wellbore was larger than that far from the wellbore. Furthermore, HCL fluid was likely to etch the fracture surface within a short propagation distance, while clean-acid fluid promoted induced fractures to propagate at a long distance. Furthermore, a slow decrease in the extension pressure in the fracture curve indirectly indicated that the acid fluid reacted with the matrix and propagated slowly, which was a sign of successful acid fracturing treatment. According to the experimental results, the acid etched width and fracture propagation distance are assumed to be two important factors for estimating the acid fracturing treatment performance.
Catherine Dorbath - One of the best experts on this subject based on the ideXlab platform.
-
Injection tests at the EGS reservoir of Soultz-sous-Forêts. Seismic response of the GPK4 stimulations
Geothermics, 2014Co-Authors: Marco Calò, Catherine Dorbath, Michel FrogneuxAbstract:Abstract The European Enhanced Geothermal System (EGS) program of Soultz-sous-Forets is organized around three wells (GPK2, GPK3, and GPK4) drilled to a depth of about 5000 m. Hydraulic stimulations were performed in order to increase the injectivity of the reservoir and the connectivity among the wells. The stimulation of GPK4 was carried out in two stages, in September 2004 and in February 2005, followed by an acidification test performed in March 2005. The stimulations produced fewer induced events than those of the other wells, with interpretation remaining difficult. In this work we present some new observations on the seismicity of the GPK4 stimulations after a complete review of the seismic bulletins collected in 2004 and 2005. Furthermore, the events were relocated using the double difference method. The new images of the seismicity are presented in temporal sequences according to the main variations of the injection parameters. The seismic events that occurred during the 2004 stimulation are grouped in a dense cloud and centered on the well Open-Hole Section, while in 2005 seismicity depicts a specific pattern suggesting that the “natural” stress field in the reservoir was not completely restored. Finally, the events recorded during the acidified test show that the reservoir behaved differently from the previous injections, which suggests that a different mechanism has controlled the induced seismicity.
-
analysis of the microseismicity induced by fluid injections at the egs site of soultz sous forets alsace france implications for the characterization of the geothermal reservoir properties
Pure and Applied Geophysics, 2008Co-Authors: Nicolas Cuenot, Catherine Dorbath, Louis DorbathAbstract:In June/July 2000, a hydraulic stimulation experiment took place at the geothermal EGS site of Soultz-sous-Forets (Alsace, France) in order to enhance the permeability of the fractured granitic massif at 5 km depth. As it is well known that fluid injections tend to induce microseismic events, a downHole and a surface seismological network have been installed to monitor the seismic activity during the stimulation test. 23400 m3 of fluid have been injected in the rock volume through the Open-Hole Section (4400 m–5000 m) of the well GPK2 at increasing rates of 30 l.s−1, 40 l.s−1 and then 50 l.s−1. More than 7200 microseismic events in the magnitude range –0.9 to 2.6 have been precisely located through a simultaneous inversion of the seismic velocity structure and location parameters. The analysis of the behavior of the seismicity relative to the hydraulic parameters gives important information about the geothermal reservoir. It appears that the evolution of the seismicity strongly depends on the variations of the injection rate: An increase or a decrease leads to changes of the velocity structure, the number and magnitude of microseismic events. This involves different hydro-mechanical processes between the fluid flow and the fracture planes, which will control the final shape of the microseismic cloud. Moreover, the study of the variations of the b-value with time suggests that the stimulation experiment produces a large proportion of small earthquakes, but records of events of magnitude higher than 2 indicate that fluid injection could reactivate structures whose dimensions allow the generation of such earthquakes.
-
Analysis of the Microseismicity Induced by Fluid Injections at the EGS Site of Soultz-sous-Forêts (Alsace, France): Implications for the Characterization of the Geothermal Reservoir Properties
Pure and Applied Geophysics, 2008Co-Authors: Nicolas Cuenot, Catherine Dorbath, Louis DorbathAbstract:In June/July 2000, a hydraulic stimulation experiment took place at the geothermal EGS site of Soultz-sous-Forêts (Alsace, France) in order to enhance the permeability of the fractured granitic massif at 5 km depth. As it is well known that fluid injections tend to induce microseismic events, a downHole and a surface seismological network have been installed to monitor the seismic activity during the stimulation test. 23400 m^3 of fluid have been injected in the rock volume through the Open-Hole Section (4400 m–5000 m) of the well GPK2 at increasing rates of 30 l.s^−1, 40 l.s^−1 and then 50 l.s^−1. More than 7200 microseismic events in the magnitude range –0.9 to 2.6 have been precisely located through a simultaneous inversion of the seismic velocity structure and location parameters. The analysis of the behavior of the seismicity relative to the hydraulic parameters gives important information about the geothermal reservoir. It appears that the evolution of the seismicity strongly depends on the variations of the injection rate: An increase or a decrease leads to changes of the velocity structure, the number and magnitude of microseismic events. This involves different hydro-mechanical processes between the fluid flow and the fracture planes, which will control the final shape of the microseismic cloud. Moreover, the study of the variations of the b -value with time suggests that the stimulation experiment produces a large proportion of small earthquakes, but records of events of magnitude higher than 2 indicate that fluid injection could reactivate structures whose dimensions allow the generation of such earthquakes.
Ruxin Zhang - One of the best experts on this subject based on the ideXlab platform.
-
investigation on acid fracturing treatment in limestone formation based on true tri axial experiment
Fuel, 2019Co-Authors: Ruxin Zhang, Mian ChenAbstract:Abstract Acid fracturing treatment is the most effective method for stimulating limestone formations, which are abundant in the northeast Sichuan basin of China. The effective acid etching improves the fracture width, resulting in high fracture conductivity, while fracture propagation behavior is always affected by discontinuities and the fractured vuggy structure. Hence, the fracture geometry differs from that in homogeneous formations. However, the fracture propagation mechanism remains unclear. In order to understand the process more clearly, a series of large-scale, true tri-axial simulation experiments were conducted for the first time to investigate the fracture initiation and propagation in limestone formations under acid fracturing treatment. Moreover, the effects of multiple factors on fracture propagation were discussed, and a 3D scanner was used to depict and describe the fracture surface etching feature. The experimental results demonstrated that natural fractures had a serious impact on the fracture initiation and propagation. The induced fracture initiated from the Open-Hole Section to form a transverse fracture, or from the natural fractures to form a longitudinal or an inclined fracture. The fracture surface was rougher in the acid fracturing than in hydraulic fracturing, owing to the non-uniform acid fluid dissolution. The black-brown remains on the fracture surface were the result of acid etching, which could be used to judge the fracture propagation direction and area. However, the roughness degree of the fracture surface near the wellbore was larger than that far from the wellbore. Furthermore, HCL fluid was likely to etch the fracture surface within a short propagation distance, while clean-acid fluid promoted induced fractures to propagate at a long distance. Furthermore, a slow decrease in the extension pressure in the fracture curve indirectly indicated that the acid fluid reacted with the matrix and propagated slowly, which was a sign of successful acid fracturing treatment. According to the experimental results, the acid etched width and fracture propagation distance are assumed to be two important factors for estimating the acid fracturing treatment performance.
-
Investigation on Hydraulic Fracture Initiation and Propagation with LPG Fracturing in Shale Formation based on True Tri-Axial Laboratory Experiments
Day 3 Wed August 29 2018, 2018Co-Authors: Ruxin Zhang, Bing Hou, Yijin Zeng, Jian ZhouAbstract:Abstract Traditional hydraulic fracturing requires lots of water and sand resulting in short fracture length and small SRV with a low production. However, a new waterless fracturing, called Liquefied Petroleum Gas (LPG) fracturing, is applied to stimulate shale formation effectively. In order to figure out the mechanism of fracture initiation and propagation in LPG fracturing, four large-scale true tri-axial fracturing simulation experiments have been conducted on shale outcrops. Meanwhile, the effects of engineering factors, pump rate and fluid viscosity, on fracture propagation behavior in the shale formation are discussed. The experimental results indicate that LPG fracturing not only activates discontinuities to form a complex fracture network, but also enhances induced fracture length to form a large SRV. Induced fractures have two initiation points, Open-Hole Section and stress concentration point of wellbore wall, and have three main propagation behaviors, crossing, shear and arrest, dilation and crossing in shale formation. A low viscosity fracturing fluid activates discontinuities resulting in complex fractures, whereas, a high viscosity fluid would like to create some main fractures without Opening discontinuities. Moreover, a high pump rate offers more energy for induced fractures to cross the discontinuities resulting in a long fracture length and large SRV. In addition, the anisotropic of shale formation and the existence of discontinuities cause signals attenuation, which increases the arrival time, resulting in location deviation of acoustic emission (AE) events in the AE monitoring. The pressure-time-energy curve, however, shows that the fracture initiation is earlier than the sample ruptured. That is, the initiation pressure is smaller than the ruptured pressure. The experiments conducted in this paper prove that the LPG fracturing indeed has some advantages than traditional hydraulic fracturing, such as long fracture length and large SRV. And then, the research results provide the theoretical basis for the LPG fracturing operation in shale formation.
Marco Calò - One of the best experts on this subject based on the ideXlab platform.
-
Injection tests at the EGS reservoir of Soultz-sous-Forêts. Seismic response of the GPK4 stimulations
Geothermics, 2014Co-Authors: Marco Calò, Catherine Dorbath, Michel FrogneuxAbstract:Abstract The European Enhanced Geothermal System (EGS) program of Soultz-sous-Forets is organized around three wells (GPK2, GPK3, and GPK4) drilled to a depth of about 5000 m. Hydraulic stimulations were performed in order to increase the injectivity of the reservoir and the connectivity among the wells. The stimulation of GPK4 was carried out in two stages, in September 2004 and in February 2005, followed by an acidification test performed in March 2005. The stimulations produced fewer induced events than those of the other wells, with interpretation remaining difficult. In this work we present some new observations on the seismicity of the GPK4 stimulations after a complete review of the seismic bulletins collected in 2004 and 2005. Furthermore, the events were relocated using the double difference method. The new images of the seismicity are presented in temporal sequences according to the main variations of the injection parameters. The seismic events that occurred during the 2004 stimulation are grouped in a dense cloud and centered on the well Open-Hole Section, while in 2005 seismicity depicts a specific pattern suggesting that the “natural” stress field in the reservoir was not completely restored. Finally, the events recorded during the acidified test show that the reservoir behaved differently from the previous injections, which suggests that a different mechanism has controlled the induced seismicity.
