Carboniferous carbonate reservoirs at the eastern edge of the Pre-Caspian Basin have undergone complex sedimentation,diagenesis and tectonism processes,and developed various reservoir space types of pores,cavities and...Carboniferous carbonate reservoirs at the eastern edge of the Pre-Caspian Basin have undergone complex sedimentation,diagenesis and tectonism processes,and developed various reservoir space types of pores,cavities and fractures with complicated combination patterns which create intricate pore-throats structure.The complex pore-throat structure leads to the complex porosity-permeability relationship,bringing great challenges for classification and evaluation of reservoirs and efficient development.Based on the comprehensive analysis on cores,thin sections,SEM,mercury intrusion,routine core analysis and various tests,this paper systematically investigated the features and main controlling factors of pore-throats structure and its impact on the porosity-permeability relationship of the four reservoir types which were pore-cavity-fracture,pore-cavity,pore-fracture and pore,and three progresses are made.(1)A set of classification and descriptive approach for pore-throat structure of Carboniferous carbonate reservoirs applied to the eastern edge of the Pre-Caspian Basin was established.Four types of pore-throat structures were developed which were wide multimodal mode,wide bimodal mode,centralized unimodal mode and asymmetry bimodal mode,respectively.The discriminant index of pore-throat structure was proposed,realizing the quantitative characterization of pore-throat structure types.(2)The microscopic heterogeneity of pore reservoir was the strongest and four types of pore-throat structures were all developed.The pore-fracture and pore-cavity-fracture reservoirs took the second place,and the microscopic heterogeneity of pore-cavity reservoir was the weakest.It was revealed that the main controlling factor of pore-throat structure was the combination patterns of reservoir space types formed by sedimentation,diagenesis and tectonism.(3)It was revealed that the development of various pore-throat structure types was the important factor affecting poroperm relationship of reservoirs.The calculation accuracy of permeability of reservoirs can be improved remarkably by subdividing the pore-throat structure types.This study deepens the understanding of pore-throat structure of complicated carbonate reservoirs,and is conducive to classification and evaluation,establishment of precise porosity-permeability relationship and highly efficient development of carbonate reservoirs.展开更多
High resolution seismic data and newly acquired logging data reveal the presence of gas hydrates in the deep-water area in the northeastern Bay of Bengal.Bottom Simulating Reflectors(BSRs)appear at 430 ms beneath the ...High resolution seismic data and newly acquired logging data reveal the presence of gas hydrates in the deep-water area in the northeastern Bay of Bengal.Bottom Simulating Reflectors(BSRs)appear at 430 ms beneath the seafloor,with the features of typical gas hydrates reported elsewhere except for some discontinuity.The BSR distribution is closely related to the position of anticline structures and turbidite channels.Anticlines provide conduits for the upward migration of gases from deeper intervals,while the turbidite sands within channels act as reservoirs for gas hydrate accumulation.High sedimentation rates in the Bengal Fan were ge-nerally favorable to produce a great amount of methane gas,providing favorable preconditions for the formation of gas hydrates.The discovery of gases in adjacent area indicates the contribution of the biogenic gas to the formation of gas hydrates.Meanwhile,seismic sections provide the evidence for the potential thermogenic gas kitchen in deep intervals.The anticline structures and the associated vertical fractures may constitute vertical fluid flowing conduits,which hydraulically connect the two deeper thermogenic petroleum systems(i.e.,rifting and Eocene-Oligocene source rocks)with the turbidite reservoirs and thus facilitate the fluid migration from the sources to the reservoirs,generating favorable conditions for gas-hydrate accumulation in such foreland setting.展开更多
基金Supported by the China Science and Technology Major Project(2017ZX05030-002)China National Petroleum Corporation Scientific Research and Technology Development Project(2019D-4309)
文摘Carboniferous carbonate reservoirs at the eastern edge of the Pre-Caspian Basin have undergone complex sedimentation,diagenesis and tectonism processes,and developed various reservoir space types of pores,cavities and fractures with complicated combination patterns which create intricate pore-throats structure.The complex pore-throat structure leads to the complex porosity-permeability relationship,bringing great challenges for classification and evaluation of reservoirs and efficient development.Based on the comprehensive analysis on cores,thin sections,SEM,mercury intrusion,routine core analysis and various tests,this paper systematically investigated the features and main controlling factors of pore-throats structure and its impact on the porosity-permeability relationship of the four reservoir types which were pore-cavity-fracture,pore-cavity,pore-fracture and pore,and three progresses are made.(1)A set of classification and descriptive approach for pore-throat structure of Carboniferous carbonate reservoirs applied to the eastern edge of the Pre-Caspian Basin was established.Four types of pore-throat structures were developed which were wide multimodal mode,wide bimodal mode,centralized unimodal mode and asymmetry bimodal mode,respectively.The discriminant index of pore-throat structure was proposed,realizing the quantitative characterization of pore-throat structure types.(2)The microscopic heterogeneity of pore reservoir was the strongest and four types of pore-throat structures were all developed.The pore-fracture and pore-cavity-fracture reservoirs took the second place,and the microscopic heterogeneity of pore-cavity reservoir was the weakest.It was revealed that the main controlling factor of pore-throat structure was the combination patterns of reservoir space types formed by sedimentation,diagenesis and tectonism.(3)It was revealed that the development of various pore-throat structure types was the important factor affecting poroperm relationship of reservoirs.The calculation accuracy of permeability of reservoirs can be improved remarkably by subdividing the pore-throat structure types.This study deepens the understanding of pore-throat structure of complicated carbonate reservoirs,and is conducive to classification and evaluation,establishment of precise porosity-permeability relationship and highly efficient development of carbonate reservoirs.
基金We wish to thank the China National Oil and Gas Exploration and Development Company(CNODC)and Hangzhou Research Institute of Geology research team for providing the seismic data and approving this publication.The research is funded by the National Natural Science Foundation of China(Nos.92055211,42076219,42006067)the Construction Project of China ASEAN Marine Seismic Data Platform and Research Center(No.1212010050017001).
文摘High resolution seismic data and newly acquired logging data reveal the presence of gas hydrates in the deep-water area in the northeastern Bay of Bengal.Bottom Simulating Reflectors(BSRs)appear at 430 ms beneath the seafloor,with the features of typical gas hydrates reported elsewhere except for some discontinuity.The BSR distribution is closely related to the position of anticline structures and turbidite channels.Anticlines provide conduits for the upward migration of gases from deeper intervals,while the turbidite sands within channels act as reservoirs for gas hydrate accumulation.High sedimentation rates in the Bengal Fan were ge-nerally favorable to produce a great amount of methane gas,providing favorable preconditions for the formation of gas hydrates.The discovery of gases in adjacent area indicates the contribution of the biogenic gas to the formation of gas hydrates.Meanwhile,seismic sections provide the evidence for the potential thermogenic gas kitchen in deep intervals.The anticline structures and the associated vertical fractures may constitute vertical fluid flowing conduits,which hydraulically connect the two deeper thermogenic petroleum systems(i.e.,rifting and Eocene-Oligocene source rocks)with the turbidite reservoirs and thus facilitate the fluid migration from the sources to the reservoirs,generating favorable conditions for gas-hydrate accumulation in such foreland setting.
