Marine shale gas resources have great potential in the south of the Sichuan Basin in China.At present,the high-quality shale gas resources at depth of 2000–3500 m are under effective development,and strategic breakth...Marine shale gas resources have great potential in the south of the Sichuan Basin in China.At present,the high-quality shale gas resources at depth of 2000–3500 m are under effective development,and strategic breakthroughs have been made in deeper shale gas resources at depth of 3500–4500 m.To promote the effective production of shale gas in this area,this study examines key factors controlling high shale gas production and presents the next exploration direction in the southern Sichuan Basin based on summarizing the geological understandings from the Lower Silurian Longmaxi Formation shale gas exploration combined with the latest results of geological evaluation.The results show that:(1)The relative sea depth in marine shelf sedimentary environment controls the development and distribution of reservoirs.In the relatively deep water area in deep-water shelf,grade-I reservoirs with a larger continuous thickness develop.The relative depth of sea in marine shelf sedimentary environment can be determined by redox conditions.The research shows that the uranium to thorium mass ratio greater than 1.25 indicates relatively deep water in anoxic reduction environment,and the uranium to thorium mass ratio of 0.75–1.25 indicates semi-deep water in weak reduction and weak oxidation environment,and the uranium to thorium mass ratio less than 0.75 indicates relatively shallow water in strong oxidation environment.(2)The propped fractures in shale reservoirs subject to fracturing treatment are generally 10–12 m high,if grade-I reservoirs are more than 10 m in continuous thickness,then all the propped section would be high-quality reserves;in this case,the longer the continuous thickness of penetrated grade-I reservoirs,the higher the production will be.(3)The shale gas reservoirs at 3500–4500 m depth in southern Sichuan are characterized by high formation pressure,high pressure coefficient,well preserved pores,good pore structure and high proportion of free gas,making them the most favorable new field for shale gas exploration;and the pressure coefficient greater than 1.2 is a necessary condition for shale gas wells to obtain high production.(4)High production wells in the deep shale gas reservoirs are those in areas where Long11-Long13 sub-beds are more than 10 m thick,with 1500 m long horizontal section,grade-I reservoirs penetration rate of over 90%,and fractured by dense cutting+high intensity sand injection+large displacement+large liquid volume.(5)The relatively deep-water area in the deep-water shelf and the area at depth of 3500–4500 m well overlap in the southern Sichuan,and the overlapping area is the most favorable shale gas exploration and development zones in the southern Sichuan in the future.With advancement in theory and technology,annual shale gas production in the southern Sichuan is expected to reach 450×108 m3.展开更多
Based on temperature and pressure of fluid inclusion, phase of organic inclusion in calcite and quartz filled in vug in the deep carbonate reservoir and the natural gas composition in Weiyuan （威远） gas field in Sic...Based on temperature and pressure of fluid inclusion, phase of organic inclusion in calcite and quartz filled in vug in the deep carbonate reservoir and the natural gas composition in Weiyuan （威远） gas field in Sichuan （四川） basin, research indicates that water soluble gas exists in deep carbonate reservoir, which reconstructs development and effusion process of water soluble gas. The overpressure formed during oil thermal cracking can reach 105-170 MPa in Sinian and Cambrian reservoir in Central Sichuan and 78-86 MPa in Cambrian reservoir in Southeast Sichuan. The high temperature caused by deep burial and overpressure caused by thermal cracking make thermal cracking gas dissolve in water so that it becomes water soluble gas. The ratios of gas to water can reach 50-90 m^3/m^3 and 10-30 m^3/m^3, respectively, in deep carbonate reservoir in Central and Southeast Sichuan. Methane dissolving in water exists in form of liquid phase. Until now, the decreases in temperature and pressure due to the uplift during 74 Ma make water soluble gas separate from water, water soluble gas pool or mixed gas pool of thermal-cracking gas and water soluble gas are modified or even destroyed in varying degrees.This may be the case of Weiyuan gas field.展开更多
The paleo-temperature evolution of Sinian reservoir of Anping （安平） 1 well was rebuilt by taking the method of apatite fission track and Easy%Ro model. The result of apatite fission track determines the accurate bu...The paleo-temperature evolution of Sinian reservoir of Anping （安平） 1 well was rebuilt by taking the method of apatite fission track and Easy%Ro model. The result of apatite fission track determines the accurate burial history and overcomes the flaw that the vitrinite reflectance is taken as paleo-temperature indicator simply. The authors used the laser Raman technique to analyze the methane present in the calcite and quartz fluid inclusions of Sinian reservoir, finding that the methane is water soluble gas. The authors also simulated the paleo-pressure of fluid inclusion by using PVTsim software and finally worked out the methane solubility in water.展开更多
基金Supported by the China National Science and Technology Major Project(2016ZX05062)the PetroChina Science and Technology Major Project(2016E-0611)
文摘Marine shale gas resources have great potential in the south of the Sichuan Basin in China.At present,the high-quality shale gas resources at depth of 2000–3500 m are under effective development,and strategic breakthroughs have been made in deeper shale gas resources at depth of 3500–4500 m.To promote the effective production of shale gas in this area,this study examines key factors controlling high shale gas production and presents the next exploration direction in the southern Sichuan Basin based on summarizing the geological understandings from the Lower Silurian Longmaxi Formation shale gas exploration combined with the latest results of geological evaluation.The results show that:(1)The relative sea depth in marine shelf sedimentary environment controls the development and distribution of reservoirs.In the relatively deep water area in deep-water shelf,grade-I reservoirs with a larger continuous thickness develop.The relative depth of sea in marine shelf sedimentary environment can be determined by redox conditions.The research shows that the uranium to thorium mass ratio greater than 1.25 indicates relatively deep water in anoxic reduction environment,and the uranium to thorium mass ratio of 0.75–1.25 indicates semi-deep water in weak reduction and weak oxidation environment,and the uranium to thorium mass ratio less than 0.75 indicates relatively shallow water in strong oxidation environment.(2)The propped fractures in shale reservoirs subject to fracturing treatment are generally 10–12 m high,if grade-I reservoirs are more than 10 m in continuous thickness,then all the propped section would be high-quality reserves;in this case,the longer the continuous thickness of penetrated grade-I reservoirs,the higher the production will be.(3)The shale gas reservoirs at 3500–4500 m depth in southern Sichuan are characterized by high formation pressure,high pressure coefficient,well preserved pores,good pore structure and high proportion of free gas,making them the most favorable new field for shale gas exploration;and the pressure coefficient greater than 1.2 is a necessary condition for shale gas wells to obtain high production.(4)High production wells in the deep shale gas reservoirs are those in areas where Long11-Long13 sub-beds are more than 10 m thick,with 1500 m long horizontal section,grade-I reservoirs penetration rate of over 90%,and fractured by dense cutting+high intensity sand injection+large displacement+large liquid volume.(5)The relatively deep-water area in the deep-water shelf and the area at depth of 3500–4500 m well overlap in the southern Sichuan,and the overlapping area is the most favorable shale gas exploration and development zones in the southern Sichuan in the future.With advancement in theory and technology,annual shale gas production in the southern Sichuan is expected to reach 450×108 m3.
基金supported by the National Basic Research Program of China (No. 2005CB422106)
文摘Based on temperature and pressure of fluid inclusion, phase of organic inclusion in calcite and quartz filled in vug in the deep carbonate reservoir and the natural gas composition in Weiyuan （威远） gas field in Sichuan （四川） basin, research indicates that water soluble gas exists in deep carbonate reservoir, which reconstructs development and effusion process of water soluble gas. The overpressure formed during oil thermal cracking can reach 105-170 MPa in Sinian and Cambrian reservoir in Central Sichuan and 78-86 MPa in Cambrian reservoir in Southeast Sichuan. The high temperature caused by deep burial and overpressure caused by thermal cracking make thermal cracking gas dissolve in water so that it becomes water soluble gas. The ratios of gas to water can reach 50-90 m^3/m^3 and 10-30 m^3/m^3, respectively, in deep carbonate reservoir in Central and Southeast Sichuan. Methane dissolving in water exists in form of liquid phase. Until now, the decreases in temperature and pressure due to the uplift during 74 Ma make water soluble gas separate from water, water soluble gas pool or mixed gas pool of thermal-cracking gas and water soluble gas are modified or even destroyed in varying degrees.This may be the case of Weiyuan gas field.
基金supported by the National Basic Research Program of China (No. 2005CB422106)
文摘The paleo-temperature evolution of Sinian reservoir of Anping （安平） 1 well was rebuilt by taking the method of apatite fission track and Easy%Ro model. The result of apatite fission track determines the accurate burial history and overcomes the flaw that the vitrinite reflectance is taken as paleo-temperature indicator simply. The authors used the laser Raman technique to analyze the methane present in the calcite and quartz fluid inclusions of Sinian reservoir, finding that the methane is water soluble gas. The authors also simulated the paleo-pressure of fluid inclusion by using PVTsim software and finally worked out the methane solubility in water.
