This work extensively investigated global tight sandstone gas, and geologically and geochemically analyzed the tight sandstone gas in China＇s Ordos, Sichuan, and Tarim basins. We compared typical tight sandstone gas ...This work extensively investigated global tight sandstone gas, and geologically and geochemically analyzed the tight sandstone gas in China＇s Ordos, Sichuan, and Tarim basins. We compared typical tight sandstone gas in China with that in North America. We proposed six conditions for the formation of China＇s tight sandstone gas, and illustrated the geological characteristics of tight sandstone gas. In China, gas-bearing tight sandstones were mainly deposited in continental lake deltas and marine-terrigenous facies basin environments, associated with coal-measure strata, and were mostly buried deeper than 2000 in under a formation pressure of 20-30 MPa, with pressure coefficients varying from overpressure to negative pressure. In other countries, tight gas bearing sandstones were dominantly deposited in marine to marine-terrigenous facies environments, occurred in coal-measure strata, and were mostly buried shallower than 2000 m in low-pressure systems. We systematically analyzed tight sandstone gas in the Ordos, Sichuan, and Tarim basins in terms of chemical compositions, geochemical characteristics of carbon isotopes, origins, and sources. Tight sandstone gas in China usually has a hydrocarbon content of 〉95%, with CH4 content 〉90%, and a generally higher dry coefficient. In the three above-mentioned large tight sandstone gas regions,δ13C1 and δJ3C2 mainly ranges from -42%o to -28%o and from -28%o to -21%o, respectively. Type III coal-measure source rocks that closely coexist with tight reservoirs are developed extensively in these gas regions. The organic petrology of source rocks and the carbon isotope compositions of gas indicate that tight sandstone gas in China is dominantly coal-derived gas generated by coal-measure strata. Our analysis of carbon isotope series shows that local isotope reversals are mainly caused by the mixing of gases of different maturities and that were generated at different stages. With increasing maturity, the reversal tendency becomes more apparent. Moreover, natural gas with medium-low maturity （e.g., Xujiahe Formation natural gas in the Sichuan Basin） presents an apparent reversal at a low-maturity stage, a normal series at a medium -maturity stage, and a reversal tendency again at a high-maturity stage. Finally, we proposed four conditions for preferred tight sandstone gas ＂sweep spots,＂ and illustrated the recoverable reserves, proven reserves, production, and exploration prospects of tight sandstone gas. The geological and geochemical characteristics, origins, sources, and exploration potential of tight sandstone gas in China from our research will be instructive for the future evaluation, prediction, and exploration of tight sandstone gas in China and abroad.展开更多
Dear authors and readers,Mission to asteroids is always a hot topic in the field of deep space exploration,since asteroids may have clues from the evolution and formation of the solar system to the origin of life.Plen...Dear authors and readers,Mission to asteroids is always a hot topic in the field of deep space exploration,since asteroids may have clues from the evolution and formation of the solar system to the origin of life.Plenty of asteroid exploration missions have been implemented in recent years,bringing astonishing scientific discoveries that greatly promote our understanding of asteroids.In the meantime,more exploration missions are in progress.Deeply understanding the dynamics environment in the vicinity of asteroids is the first step in mission design.Astrodynamics problem becomes the key to the success of the missions,which goes through the entire mission flow,including target selection,transfer trajectory and mission orbital design,stability analysis for proximity and surface operation,guidance and control for precise landing,and so on.展开更多
In June 2017, BGP’s fleet Explorer started the Origin project in Australia, onboard was a handsome and optimistic Australian electrician James, a light-handed young man at Engine Department.Turning waste into wealth ...In June 2017, BGP’s fleet Explorer started the Origin project in Australia, onboard was a handsome and optimistic Australian electrician James, a light-handed young man at Engine Department.Turning waste into wealth In the fleet, James is a well-known “craftsman”. By turning wastes into useful things, James has saved nearly USD 10,000 for the company. He collected discarded cables from the garbage bin.展开更多
基金supported by the Petro China Major Scientific and Technical Project (No.: 2014B-0608)the National Science and Technology Major Project of China (NO.: 2011ZX5001-001)
文摘This work extensively investigated global tight sandstone gas, and geologically and geochemically analyzed the tight sandstone gas in China＇s Ordos, Sichuan, and Tarim basins. We compared typical tight sandstone gas in China with that in North America. We proposed six conditions for the formation of China＇s tight sandstone gas, and illustrated the geological characteristics of tight sandstone gas. In China, gas-bearing tight sandstones were mainly deposited in continental lake deltas and marine-terrigenous facies basin environments, associated with coal-measure strata, and were mostly buried deeper than 2000 in under a formation pressure of 20-30 MPa, with pressure coefficients varying from overpressure to negative pressure. In other countries, tight gas bearing sandstones were dominantly deposited in marine to marine-terrigenous facies environments, occurred in coal-measure strata, and were mostly buried shallower than 2000 m in low-pressure systems. We systematically analyzed tight sandstone gas in the Ordos, Sichuan, and Tarim basins in terms of chemical compositions, geochemical characteristics of carbon isotopes, origins, and sources. Tight sandstone gas in China usually has a hydrocarbon content of 〉95%, with CH4 content 〉90%, and a generally higher dry coefficient. In the three above-mentioned large tight sandstone gas regions,δ13C1 and δJ3C2 mainly ranges from -42%o to -28%o and from -28%o to -21%o, respectively. Type III coal-measure source rocks that closely coexist with tight reservoirs are developed extensively in these gas regions. The organic petrology of source rocks and the carbon isotope compositions of gas indicate that tight sandstone gas in China is dominantly coal-derived gas generated by coal-measure strata. Our analysis of carbon isotope series shows that local isotope reversals are mainly caused by the mixing of gases of different maturities and that were generated at different stages. With increasing maturity, the reversal tendency becomes more apparent. Moreover, natural gas with medium-low maturity （e.g., Xujiahe Formation natural gas in the Sichuan Basin） presents an apparent reversal at a low-maturity stage, a normal series at a medium -maturity stage, and a reversal tendency again at a high-maturity stage. Finally, we proposed four conditions for preferred tight sandstone gas ＂sweep spots,＂ and illustrated the recoverable reserves, proven reserves, production, and exploration prospects of tight sandstone gas. The geological and geochemical characteristics, origins, sources, and exploration potential of tight sandstone gas in China from our research will be instructive for the future evaluation, prediction, and exploration of tight sandstone gas in China and abroad.
文摘Dear authors and readers,Mission to asteroids is always a hot topic in the field of deep space exploration,since asteroids may have clues from the evolution and formation of the solar system to the origin of life.Plenty of asteroid exploration missions have been implemented in recent years,bringing astonishing scientific discoveries that greatly promote our understanding of asteroids.In the meantime,more exploration missions are in progress.Deeply understanding the dynamics environment in the vicinity of asteroids is the first step in mission design.Astrodynamics problem becomes the key to the success of the missions,which goes through the entire mission flow,including target selection,transfer trajectory and mission orbital design,stability analysis for proximity and surface operation,guidance and control for precise landing,and so on.
文摘In June 2017, BGP’s fleet Explorer started the Origin project in Australia, onboard was a handsome and optimistic Australian electrician James, a light-handed young man at Engine Department.Turning waste into wealth In the fleet, James is a well-known “craftsman”. By turning wastes into useful things, James has saved nearly USD 10,000 for the company. He collected discarded cables from the garbage bin.
