Unconventional gas in the Sichuan Basin mainly includes shale gas and tight gas.The development of shale gas is mainly concentrated in the Ordovician Wufeng Formation-Silurian Longmaxi Formation,but has not made any s...Unconventional gas in the Sichuan Basin mainly includes shale gas and tight gas.The development of shale gas is mainly concentrated in the Ordovician Wufeng Formation-Silurian Longmaxi Formation,but has not made any significant breakthrough in the Cambrian Qiongzhusi Formation marine shale regardless of exploration efforts for years.The commercial development of tight sandstone gas is mainly concentrated in the Jurassic Shaximiao Formation,but has not been realized in the widespread and thick Triassic Xujiahe Formation.Depending on the geological characteristics of the Qiongzhusi Formation and Xujiahe Formation,the feedback of old wells was analyzed.Then,combining with the accumulation mechanisms of con-ventional gas and shale gas,as well as the oil/gas shows during drilling,changes in production and pressure during develop-ment,and other characteristics,it was proposed to change the exploration and development strategy from source and reservoir exploration to carrier beds exploration.With the combination of effective source rock,effective carrier beds and effective sand-stone or shale as the exploration target,a model of unconventional gas accumulation and enrichment in carrier beds was built.Under the guidance of this study,two significant results have been achieved in practice.First,great breakthrough was made in exploration of the silty shale with low organic matter abundance in the Qiongzhusi Formation,which breaks the traditional approach to prospect shale gas only in organic-rich black shales and realizes a breakthrough in new areas,new layers and new types of shale gas and a transformation of exploration and development of shale gas from single-layer system,Longmaxi For-mation,to multi-layer system in the Sichuan Basin.Second,exploration breakthrough and high-efficient development were re-alized for difficult-to-produce tight sandstone gas reserves in the Xujiahe Formation,which helps address the challenges of low production and unstable production of fracture zones in the Xujiahe Formation,promote the transformation of tight sandstone gas from reserves without production to effective production,and enhance the exploration and development potential of tight sandstonegas.展开更多
Effective carrier system comprises carrier beds which transport hydrocarbons.The spatial and temporal effectiveness of carrier system is identified according to the relevance of hydrocarbon show,hydrocarbon inclusion ...Effective carrier system comprises carrier beds which transport hydrocarbons.The spatial and temporal effectiveness of carrier system is identified according to the relevance of hydrocarbon show,hydrocarbon inclusion and sealing ability of fault to hydrocarbons distribution,together with matching relation of activity history of fault and hydrocarbon generation history of source rock.On the basis of the above considerations,transporting ability of effective carrier system can be evaluated using parameters such as fluid potential,porosity and permeability,spatial coefficient of effective pathway as well as activity rate of fault.Additionally,a new concept of "transporting threshold porosity" was proposed.Five styles of effective carrier systems were established in Gaoyou Sag,displaying either layered or zonal distribution characteristics,and transporting time ranges from the sedimentary time of E2d2 to early stage of sanduo uplift.Effective carrier systems can be described to be lowly-efficient and highly-efficient.Major faults (convex or steep fault plane) with activity rate greater than 20 m/Ma and structure ridges of sand layers with spatial coefficient of effective pathway greater than 25% are defined to be highly-efficient carrier beds.Hydrocarbons are concentrated around high-efficient carrier beds and E1 f traps of northern shanian area are predicted to have great potential.展开更多
基金Sinopec Science and Technology Major Project (P22081)China National Science and Technology Major Project (2016ZX05002-004)
文摘Unconventional gas in the Sichuan Basin mainly includes shale gas and tight gas.The development of shale gas is mainly concentrated in the Ordovician Wufeng Formation-Silurian Longmaxi Formation,but has not made any significant breakthrough in the Cambrian Qiongzhusi Formation marine shale regardless of exploration efforts for years.The commercial development of tight sandstone gas is mainly concentrated in the Jurassic Shaximiao Formation,but has not been realized in the widespread and thick Triassic Xujiahe Formation.Depending on the geological characteristics of the Qiongzhusi Formation and Xujiahe Formation,the feedback of old wells was analyzed.Then,combining with the accumulation mechanisms of con-ventional gas and shale gas,as well as the oil/gas shows during drilling,changes in production and pressure during develop-ment,and other characteristics,it was proposed to change the exploration and development strategy from source and reservoir exploration to carrier beds exploration.With the combination of effective source rock,effective carrier beds and effective sand-stone or shale as the exploration target,a model of unconventional gas accumulation and enrichment in carrier beds was built.Under the guidance of this study,two significant results have been achieved in practice.First,great breakthrough was made in exploration of the silty shale with low organic matter abundance in the Qiongzhusi Formation,which breaks the traditional approach to prospect shale gas only in organic-rich black shales and realizes a breakthrough in new areas,new layers and new types of shale gas and a transformation of exploration and development of shale gas from single-layer system,Longmaxi For-mation,to multi-layer system in the Sichuan Basin.Second,exploration breakthrough and high-efficient development were re-alized for difficult-to-produce tight sandstone gas reserves in the Xujiahe Formation,which helps address the challenges of low production and unstable production of fracture zones in the Xujiahe Formation,promote the transformation of tight sandstone gas from reserves without production to effective production,and enhance the exploration and development potential of tight sandstonegas.
基金Project(P08045)supported by Geological Research Institute of Jiangsu Oilfield Company,SINOPEC,China
文摘Effective carrier system comprises carrier beds which transport hydrocarbons.The spatial and temporal effectiveness of carrier system is identified according to the relevance of hydrocarbon show,hydrocarbon inclusion and sealing ability of fault to hydrocarbons distribution,together with matching relation of activity history of fault and hydrocarbon generation history of source rock.On the basis of the above considerations,transporting ability of effective carrier system can be evaluated using parameters such as fluid potential,porosity and permeability,spatial coefficient of effective pathway as well as activity rate of fault.Additionally,a new concept of "transporting threshold porosity" was proposed.Five styles of effective carrier systems were established in Gaoyou Sag,displaying either layered or zonal distribution characteristics,and transporting time ranges from the sedimentary time of E2d2 to early stage of sanduo uplift.Effective carrier systems can be described to be lowly-efficient and highly-efficient.Major faults (convex or steep fault plane) with activity rate greater than 20 m/Ma and structure ridges of sand layers with spatial coefficient of effective pathway greater than 25% are defined to be highly-efficient carrier beds.Hydrocarbons are concentrated around high-efficient carrier beds and E1 f traps of northern shanian area are predicted to have great potential.
