There have been at least 29 groups of estimates on the global natural gas hydrate(NGH)resource since1973,varying greatly with up to 10,000 times and showing a decreasing trend with time.For the South China Sea(SCS),35...There have been at least 29 groups of estimates on the global natural gas hydrate(NGH)resource since1973,varying greatly with up to 10,000 times and showing a decreasing trend with time.For the South China Sea(SCS),35 groups of estimations were conducted on NGH resource potential since 2000,while these estimates kept almost the same with time,varying between 60 and 90 billion tons of oil equivalent(toe).What are the key factors controlling the variation trend?What are the implications of these variations for the NGH development in the world and the SCS?By analyzing the investigation characteristics of NGH resources in the world,this study divided the evaluation process into six stages and confirmed four essential factors for controlling the variations of estimates.Results indicated that the reduction trend reflects an improved understanding of the NGH formation mechanism and advancement in the resource evaluation methods,and promoted more objective evaluation results.Furthermore,the analysis process and improved evaluation method was applied to evaluate the NGH resources in the SCS,showing the similar decreasing trend of NGH resources with time.By utilizing the decreasing trend model,the predicted recoverable resources in the world and the SCS are(205-500)×10^(12)m^(3)and(0.8-6.5)×10^(12)m^(3),respectively,accounting for 20%of the total conventional oil and gas resources.Recoverable NGH resource in the SCS is only about 4%-6%of the previous estimates of 60-90 billion toe.If extracted completely,it only can support the sustainable development of China for 7 years at the current annual consumption level of oil and gas.NGH cannot be the main energy resource in future due to its low resource potential and lack of advantages in recovery.展开更多
The Qinghai-Tibet Plateau(also referred to as the Plateau)is the largest area bearing alpine permafrost region in the world and thus is endowed with great formation conditions and prospecting potential of natural gas ...The Qinghai-Tibet Plateau(also referred to as the Plateau)is the largest area bearing alpine permafrost region in the world and thus is endowed with great formation conditions and prospecting potential of natural gas hydrates(NGH).Up to now,one NGH accumulation,two inferred NGH accumulations,and a series of NGH-related anomalous indicators have been discovered in the Plateau,with NGH resources predicted to be up to 8.88×10^(12) m^(3).The NGH in the Qinghai-Tibet Plateau have complex gas components and are dominated by deep thermogenic gas.They occur in the Permian-Jurassic strata and are subject to thin permafrost and sensitive to environment.Furthermore,they are distinctly different from the NGH in the high-latitude permafrost in the arctic regions and are more different from marine NGH.The formation of the NGH in the Plateau obviously couples with the uplift and permafrost evolution of the Plateau in spatial-temporal terms.The permafrost and NGH in the Qilian Mountains and the main body of the Qinghai-Tibet Plateau possibly formed during 2.0–1.28 Ma BP and about 0.8 Ma BP,respectively.Under the context of global warming,the permafrost in the Qinghai-Tibet Plateau is continually degrading,which will lead to the changes in the stability of NGH.Therefore,The NGH of the Qinghai-Tibet Plateau can not be ignored in the study of the global climate change and ecological environment.展开更多
To meet the requirements of marine natural gas hydrate exploitation,it is necessary to improve the penetration of completion sand control string in the large curvature borehole.In this study,large curvature test wells...To meet the requirements of marine natural gas hydrate exploitation,it is necessary to improve the penetration of completion sand control string in the large curvature borehole.In this study,large curvature test wells were selected to carry out the running test of sand control string with pre-packed screen.Meanwhile,the running simulation was performed by using the Landmark software.The results show that the sand control packer and screen can be run smoothly in the wellbore with a dogleg angle of more than 20°/30 m and keep the structure stable.Additionally,the comprehensive friction coefficient is 0.4,under which and the simulation shows that the sand control string for hydrate exploitation can be run smoothly.These findings have important guiding significance for running the completion sand control string in natural gas hydrate exploitation.展开更多
基金financially supported by the CAS consultation project(2019-ZW11-Z-035)the National Basic Research Program of China(973)(2006CB202300,2011CB201100)China High-Tech R&D(863)Program Project(2013AA092600)。
文摘There have been at least 29 groups of estimates on the global natural gas hydrate(NGH)resource since1973,varying greatly with up to 10,000 times and showing a decreasing trend with time.For the South China Sea(SCS),35 groups of estimations were conducted on NGH resource potential since 2000,while these estimates kept almost the same with time,varying between 60 and 90 billion tons of oil equivalent(toe).What are the key factors controlling the variation trend?What are the implications of these variations for the NGH development in the world and the SCS?By analyzing the investigation characteristics of NGH resources in the world,this study divided the evaluation process into six stages and confirmed four essential factors for controlling the variations of estimates.Results indicated that the reduction trend reflects an improved understanding of the NGH formation mechanism and advancement in the resource evaluation methods,and promoted more objective evaluation results.Furthermore,the analysis process and improved evaluation method was applied to evaluate the NGH resources in the SCS,showing the similar decreasing trend of NGH resources with time.By utilizing the decreasing trend model,the predicted recoverable resources in the world and the SCS are(205-500)×10^(12)m^(3)and(0.8-6.5)×10^(12)m^(3),respectively,accounting for 20%of the total conventional oil and gas resources.Recoverable NGH resource in the SCS is only about 4%-6%of the previous estimates of 60-90 billion toe.If extracted completely,it only can support the sustainable development of China for 7 years at the current annual consumption level of oil and gas.NGH cannot be the main energy resource in future due to its low resource potential and lack of advantages in recovery.
基金the China Geological Survey entitled Comprehensive Survey of Terrestrial NGH Resources(DD20190102).
文摘The Qinghai-Tibet Plateau(also referred to as the Plateau)is the largest area bearing alpine permafrost region in the world and thus is endowed with great formation conditions and prospecting potential of natural gas hydrates(NGH).Up to now,one NGH accumulation,two inferred NGH accumulations,and a series of NGH-related anomalous indicators have been discovered in the Plateau,with NGH resources predicted to be up to 8.88×10^(12) m^(3).The NGH in the Qinghai-Tibet Plateau have complex gas components and are dominated by deep thermogenic gas.They occur in the Permian-Jurassic strata and are subject to thin permafrost and sensitive to environment.Furthermore,they are distinctly different from the NGH in the high-latitude permafrost in the arctic regions and are more different from marine NGH.The formation of the NGH in the Plateau obviously couples with the uplift and permafrost evolution of the Plateau in spatial-temporal terms.The permafrost and NGH in the Qilian Mountains and the main body of the Qinghai-Tibet Plateau possibly formed during 2.0–1.28 Ma BP and about 0.8 Ma BP,respectively.Under the context of global warming,the permafrost in the Qinghai-Tibet Plateau is continually degrading,which will lead to the changes in the stability of NGH.Therefore,The NGH of the Qinghai-Tibet Plateau can not be ignored in the study of the global climate change and ecological environment.
基金supported jointly by one of the major projects of Basic and Applied Basic Research in Guangdong Province“Key Basic Theory Research for Natural Gas Hydrate Trial Production in Shenhu Pilot Test Area”(2020B0301030003)the project from Southern Marine Science&Engineering Guangdong Laboratory Guangzhou City“Research on New Closed Circulation Drilling Technology without Riser”(GML2019ZD0501)the special project for hydrate from China Geological Survey“Trial Production Implementation for Natural Gas Hydrate in Shenhu Pilot Test Area”(DD20190226)。
文摘To meet the requirements of marine natural gas hydrate exploitation,it is necessary to improve the penetration of completion sand control string in the large curvature borehole.In this study,large curvature test wells were selected to carry out the running test of sand control string with pre-packed screen.Meanwhile,the running simulation was performed by using the Landmark software.The results show that the sand control packer and screen can be run smoothly in the wellbore with a dogleg angle of more than 20°/30 m and keep the structure stable.Additionally,the comprehensive friction coefficient is 0.4,under which and the simulation shows that the sand control string for hydrate exploitation can be run smoothly.These findings have important guiding significance for running the completion sand control string in natural gas hydrate exploitation.
