The Guide sedimentary basin is located in the northeastern part of Qinghai-Xizang Plateau,which is rich in geothermal resources.However,exploitation of the geothermal resources has so far been limited,because of limit...The Guide sedimentary basin is located in the northeastern part of Qinghai-Xizang Plateau,which is rich in geothermal resources.However,exploitation of the geothermal resources has so far been limited,because of limited understanding of the resources quantity and storage gained from scientific researches.In this study,using a typical cross section across the basin and taking into account its geothermal and geological conditions,a new waterheat coupled model was built and associated modelling was done by the software TOUGH2.During modelling process,the accuracy and applicability of the model was confirmed through the calibration of relevant parameters for modelling the heat and water transport and the formation of geothermal reservoir across the basin,with particular focus on the Neogene geothermal field.Results show that the groundwater that flows from the basin margins to the center is heated by the Neogene and Paleogene sedimentary rocks with high geothermal gradients.Since the east-west extending fault F1 is conductive,it acts as preferential flow paths which on one hand provide additional and rapid flows to the thermal reservoir;and on the other hand,cool down the thermal water to a certain extent due to the infiltration of shallower water sources in the vicinity of the fault.Furthermore,the estimated geothermal resources quantity is close to that of previous studies.In comparison with the Paleogene rock formations,the Neogene geothermal reservoir shows a better nature in terms of water content,aquifer permeability and resources exploitability,although the resource quantity of the Paleogene reservoir is considerable.展开更多
As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.B...As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.展开更多
基金This work was supported by grants from National Natural Science Foundation of China(No.41402231)geothermal survey project of China Geological Survey(No.DD20190128)+1 种基金Natural Science Foundation of Hebei Province China(No.D2019330003)S&T Program of Hebei China(No.20374201D).
文摘The Guide sedimentary basin is located in the northeastern part of Qinghai-Xizang Plateau,which is rich in geothermal resources.However,exploitation of the geothermal resources has so far been limited,because of limited understanding of the resources quantity and storage gained from scientific researches.In this study,using a typical cross section across the basin and taking into account its geothermal and geological conditions,a new waterheat coupled model was built and associated modelling was done by the software TOUGH2.During modelling process,the accuracy and applicability of the model was confirmed through the calibration of relevant parameters for modelling the heat and water transport and the formation of geothermal reservoir across the basin,with particular focus on the Neogene geothermal field.Results show that the groundwater that flows from the basin margins to the center is heated by the Neogene and Paleogene sedimentary rocks with high geothermal gradients.Since the east-west extending fault F1 is conductive,it acts as preferential flow paths which on one hand provide additional and rapid flows to the thermal reservoir;and on the other hand,cool down the thermal water to a certain extent due to the infiltration of shallower water sources in the vicinity of the fault.Furthermore,the estimated geothermal resources quantity is close to that of previous studies.In comparison with the Paleogene rock formations,the Neogene geothermal reservoir shows a better nature in terms of water content,aquifer permeability and resources exploitability,although the resource quantity of the Paleogene reservoir is considerable.
基金funded by the National Natural Science Foundation of China(Grant No.NSFC51374147)the German Society for Petroleum and Coal Science and Technology(Grant No.DGMK680-4)
文摘As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.
