Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and lo...Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and low recovery factors.In this study,combined core displacement and nuclear magnetic resonance(NMR)experiments explored the reservoir gas−water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection.Consequently,for fracture core,the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion,whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores.Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability,especially for fracture core.The remaining gas distribution and the content are related to the core properties.Compared with pore cores,the water invasion rate strongly influences the residual gas distribution in fracture core.The results enhance the understanding of the water invasion mechanism,gas injection to resume production and the remaining gas distribution,so as to improve the recovery factors of carbonate gas reservoirs.展开更多
CO_2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can be used for both energy exploitation and CO_2 geological sequestration. Here, a 3-D, "two-spot" pattern well mod...CO_2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can be used for both energy exploitation and CO_2 geological sequestration. Here, a 3-D, "two-spot" pattern well model is developed to analyze the mechanism of CO_2-water displacement and heat extraction. To obtain a deeper understanding of CO_2-geothermal system under some more realistic conditions, heterogeneity of reservoir's hydrological properties is taken into account. Due to the fortissimo mobility of CO_2, as long as the existence of highly permeable zone between the two wells, it is more likely to flow through the highly permeable zone to reach the production well, even though the flow path is longer. The preferential flow shortens circulation time and reduces heat-exchange area, probably leading to early thermal breakthrough, which makes the production fluid temperature decrease rapidly. The analyses of flow dynamics of CO_2-water fluid and heat may be useful for future design of a CO_2-based geothermal development system.展开更多
基金Project(2016ZX05017)supported by the China National Science and Technology Major Project
文摘Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and low recovery factors.In this study,combined core displacement and nuclear magnetic resonance(NMR)experiments explored the reservoir gas−water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection.Consequently,for fracture core,the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion,whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores.Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability,especially for fracture core.The remaining gas distribution and the content are related to the core properties.Compared with pore cores,the water invasion rate strongly influences the residual gas distribution in fracture core.The results enhance the understanding of the water invasion mechanism,gas injection to resume production and the remaining gas distribution,so as to improve the recovery factors of carbonate gas reservoirs.
基金supported by the National Natural Science Foundation of China (Grant No.41272254 and No.41572215)
文摘CO_2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can be used for both energy exploitation and CO_2 geological sequestration. Here, a 3-D, "two-spot" pattern well model is developed to analyze the mechanism of CO_2-water displacement and heat extraction. To obtain a deeper understanding of CO_2-geothermal system under some more realistic conditions, heterogeneity of reservoir's hydrological properties is taken into account. Due to the fortissimo mobility of CO_2, as long as the existence of highly permeable zone between the two wells, it is more likely to flow through the highly permeable zone to reach the production well, even though the flow path is longer. The preferential flow shortens circulation time and reduces heat-exchange area, probably leading to early thermal breakthrough, which makes the production fluid temperature decrease rapidly. The analyses of flow dynamics of CO_2-water fluid and heat may be useful for future design of a CO_2-based geothermal development system.
