In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)...In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)model that can simultaneously consider the fracture evolution and non-Darcy flow dynamics in studying the thermo-hydro-mechanical(THM)coupling processes for heat extraction in geothermal reservoir.We further employed the model on the Habanero enhanced geothermal systems(EGS)project located in Australia.First,our findings illustrate a clear spatial-temporal variation in the thermal stress and pressure perturbations,as well as uneven spatial distribution of shear failure in 3D fracture networks.Activated shear failure is mainly concentrated in the first fracture cluster.Secondly,channeling flow have also been observed in DFNs during heat extraction and are further intensified by the expansion of fractures driven by thermal stresses.Moreover,the combined effect of non-Darcy flow and fracture evolution triggers a rapid decline in the resulting heat rate and temperature.The NR-DFN model framework and the Habanero EGS's results illustrate the importance of both fracture evolution and non-Darcy flow on the efficiency of EGS production and have the potential to promote the development of more sustainable and efficient EGS operations for stakeholders.展开更多
In this work, a novel thermal–hydraulic–mechanical (THM) coupling model is developed, where the real geological parameters of the reservoir properties are embedded. Accordingly, nine schemes of CO_(2) injection well...In this work, a novel thermal–hydraulic–mechanical (THM) coupling model is developed, where the real geological parameters of the reservoir properties are embedded. Accordingly, nine schemes of CO_(2) injection well (IW) and CH_(4) production well (PW) are established, aiming to explore the behavior of free gases after CO_(2) is injected into the depleted Wufeng–Longmaxi shale. The results indicate the free CH4 or CO2 content in the shale fractures/matrix is invariably heterogeneous. The CO_(2) involvement facilitates the ratio of free CH_(4)/CO_(2) in the matrix to that in the fractures declines and tends to be stable with time. Different combinations of IW–PWs induce a difference in the ratio of the free CH4 to the free CO_(2), in the ratio of the free CH_(4)/CO_(2) in the matrix to that in the fractures, in the content of the recovered free CH_(4), and in the content of the trapped free CO_(2). Basically, when the IW locates at the bottom Wufeng–Longmaxi shale, a farther IW–PWs distance allows more CO2 in the free phase to be trapped;furthermore, no matter where the IW is, a shorter IW–PWs distance benefits by getting more CH_(4) in the free phase recovered from the depleted Wufeng–Longmaxi shale. Hopefully, this work is helpful in gaining knowledge about the shale-based CO_(2) injection technique.展开更多
基金funded by the National Natural Science Foundation of China (No.U22A20166)Science and Technology Foundation of Guizhou Province (No.QKHJC-ZK[2023]YB074)+2 种基金Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical EngineeringInstitute of Rock and Soil MechanicsChinese Academy of Sciences (No.SKLGME022009)。
文摘In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)model that can simultaneously consider the fracture evolution and non-Darcy flow dynamics in studying the thermo-hydro-mechanical(THM)coupling processes for heat extraction in geothermal reservoir.We further employed the model on the Habanero enhanced geothermal systems(EGS)project located in Australia.First,our findings illustrate a clear spatial-temporal variation in the thermal stress and pressure perturbations,as well as uneven spatial distribution of shear failure in 3D fracture networks.Activated shear failure is mainly concentrated in the first fracture cluster.Secondly,channeling flow have also been observed in DFNs during heat extraction and are further intensified by the expansion of fractures driven by thermal stresses.Moreover,the combined effect of non-Darcy flow and fracture evolution triggers a rapid decline in the resulting heat rate and temperature.The NR-DFN model framework and the Habanero EGS's results illustrate the importance of both fracture evolution and non-Darcy flow on the efficiency of EGS production and have the potential to promote the development of more sustainable and efficient EGS operations for stakeholders.
基金This study was financially supported by the National Natural Science Foundation of China(Grant Nos.51704197 and 11872258)。
文摘In this work, a novel thermal–hydraulic–mechanical (THM) coupling model is developed, where the real geological parameters of the reservoir properties are embedded. Accordingly, nine schemes of CO_(2) injection well (IW) and CH_(4) production well (PW) are established, aiming to explore the behavior of free gases after CO_(2) is injected into the depleted Wufeng–Longmaxi shale. The results indicate the free CH4 or CO2 content in the shale fractures/matrix is invariably heterogeneous. The CO_(2) involvement facilitates the ratio of free CH_(4)/CO_(2) in the matrix to that in the fractures declines and tends to be stable with time. Different combinations of IW–PWs induce a difference in the ratio of the free CH4 to the free CO_(2), in the ratio of the free CH_(4)/CO_(2) in the matrix to that in the fractures, in the content of the recovered free CH_(4), and in the content of the trapped free CO_(2). Basically, when the IW locates at the bottom Wufeng–Longmaxi shale, a farther IW–PWs distance allows more CO2 in the free phase to be trapped;furthermore, no matter where the IW is, a shorter IW–PWs distance benefits by getting more CH_(4) in the free phase recovered from the depleted Wufeng–Longmaxi shale. Hopefully, this work is helpful in gaining knowledge about the shale-based CO_(2) injection technique.
