Gas breakthrough pressure is a key parameter to evaluate the sealing capacity of caprock,and it also plays important roles in safety and capacity of CO_(2)geological storage.Based on the published experimental results...Gas breakthrough pressure is a key parameter to evaluate the sealing capacity of caprock,and it also plays important roles in safety and capacity of CO_(2)geological storage.Based on the published experimental results,we present numerical simulations on CO_(2)breakthrough pressure in unsaturated low-permeability rock under 9 multiple P-T conditions(which can keep CO_(2)in gaseous,liquid and supercritical states)and thus,a numerical method which can be used to accurately predict CO_(2)breakthrough pressure on rock-core scale is proposed.The simulation results show that CO_(2)breakthrough pressure and breakthrough time are exponential correlated with P-T conditions.Meanwhile,pressure has stronger effects on experimental results than that of temperature.Moreover,we performed sensitivity studies on the pore distribution indexλ(0.6,0.7,0.8,and 0.9)in van Genuchten-Muale model.Results show that with the increase ofλ,CO_(2)breakthrough pressure and breakthrough time both show decreasing trends.In other words,the larger the value ofλis,the better the permeability of the caprock is,and the worse the CO_(2)sealing capacity is.The numerical method established in this study can provide an important reference for the prediction of gas breakthrough pressure on rock-core scale and for related numerical studies.展开更多
Shale gas is a resource of emerging importance in the energy field.Many countries in the world have been making big financial investments in this area.Carboniferous shale in the eastern Qaidam Basin shows good explora...Shale gas is a resource of emerging importance in the energy field.Many countries in the world have been making big financial investments in this area.Carboniferous shale in the eastern Qaidam Basin shows good exploration prospects,but limited research and exploration work for shale oil and gas resources has been undertaken.Geochemical analyses were performed on shale derived from the Upper Carboniferous Hurleg Formation in the eastern Qaidam Basin,Qinghai Province,and secondary electron imaging capability of a Field Emission scanning electron microscope （FE-SEM） was used to characterize the microstructure of the shale.The reservoir and exploitation potential of the studied shale was assessed by comparison with research results obtained from the Barnett Formation shale in Fort Worth Basin,North America and the Basin shale of Sichuan province.The results indicate that the eastern Qaidam Basin Carboniferous shale is high-quality source rock.There are four major microstructural types in the study area：matrix intergranular pores,dissolution pores,intergranular pores,and micro-fractures.The size of the micropores varies from 6-633 nm,the majority of which is between 39-200 nm,with a relatively small number of micro-scale pores ranging from 0.13-1 μtm.The pore characteristics of the studied shales are similar to the North American and Sichuanese shales,indicating that they have good reservoir potential.No micropores are present in the organic matter,which is induced by its composition; instead we found an important lamellar structure in the organic matter.These micropores and microfractures are abundant,and are connected to natural visible cracks that form the network pore system,which controls the storage and migration of shale gas.This connectivity is favorable for shale gas exploitation,providing great scientific potential and practical value.展开更多
基金supported by Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.SKLGME021010)funded by the National Natural Science Foundation of China(Grant No.41702251 and 42141010)the MOE Key Laboratory of Groundwater Circulation and Environmental Evolution。
文摘Gas breakthrough pressure is a key parameter to evaluate the sealing capacity of caprock,and it also plays important roles in safety and capacity of CO_(2)geological storage.Based on the published experimental results,we present numerical simulations on CO_(2)breakthrough pressure in unsaturated low-permeability rock under 9 multiple P-T conditions(which can keep CO_(2)in gaseous,liquid and supercritical states)and thus,a numerical method which can be used to accurately predict CO_(2)breakthrough pressure on rock-core scale is proposed.The simulation results show that CO_(2)breakthrough pressure and breakthrough time are exponential correlated with P-T conditions.Meanwhile,pressure has stronger effects on experimental results than that of temperature.Moreover,we performed sensitivity studies on the pore distribution indexλ(0.6,0.7,0.8,and 0.9)in van Genuchten-Muale model.Results show that with the increase ofλ,CO_(2)breakthrough pressure and breakthrough time both show decreasing trends.In other words,the larger the value ofλis,the better the permeability of the caprock is,and the worse the CO_(2)sealing capacity is.The numerical method established in this study can provide an important reference for the prediction of gas breakthrough pressure on rock-core scale and for related numerical studies.
基金funded by grants from the China Geological Survey program (No. 201201130400003)
文摘Shale gas is a resource of emerging importance in the energy field.Many countries in the world have been making big financial investments in this area.Carboniferous shale in the eastern Qaidam Basin shows good exploration prospects,but limited research and exploration work for shale oil and gas resources has been undertaken.Geochemical analyses were performed on shale derived from the Upper Carboniferous Hurleg Formation in the eastern Qaidam Basin,Qinghai Province,and secondary electron imaging capability of a Field Emission scanning electron microscope （FE-SEM） was used to characterize the microstructure of the shale.The reservoir and exploitation potential of the studied shale was assessed by comparison with research results obtained from the Barnett Formation shale in Fort Worth Basin,North America and the Basin shale of Sichuan province.The results indicate that the eastern Qaidam Basin Carboniferous shale is high-quality source rock.There are four major microstructural types in the study area：matrix intergranular pores,dissolution pores,intergranular pores,and micro-fractures.The size of the micropores varies from 6-633 nm,the majority of which is between 39-200 nm,with a relatively small number of micro-scale pores ranging from 0.13-1 μtm.The pore characteristics of the studied shales are similar to the North American and Sichuanese shales,indicating that they have good reservoir potential.No micropores are present in the organic matter,which is induced by its composition; instead we found an important lamellar structure in the organic matter.These micropores and microfractures are abundant,and are connected to natural visible cracks that form the network pore system,which controls the storage and migration of shale gas.This connectivity is favorable for shale gas exploitation,providing great scientific potential and practical value.
