Gas Accumulation Regularity Of Yingcheng Formation In Fulongquan Sag,Songliao Basin

The subject of this paper is Yingcheng Formation in Fulongquan sag,Songliao Basin.Comprehensive application of geology,seismology,logging and other means study the sedimentary feature,the structural characteristics,pool-forming history and the pool-forming conditions.First,based on cores,logging and seismic data to establish stratigraphic framework of Yingcheng Formation.The sedimentary feature of Yingcheng Formation,structural history,fracture feature and trap characteristics are analyzed based on the stratigraphic framework.Then,combining with the study of source-reservoir-seal assemblage discusses the regularity of gas enrichment of Yingcheng Formation.The understanding and results obtained are as follows:(1)The study established 26 contrast sections,and divided the Yingcheng Formation into 4 sections and 24 layers.Combining with regional geological background,lithologic characteristics and logging data distinguishes 3 sedimentary facies types including the fan delta,braided river delta and lacustrine facies,and further identifies 6 subfacies and 11 micro-facies.The dark mudstone in the lower part of Yingcheng Formation is good source rocks.The study area mainly develops the siltstone,fine sandstone,coarse sandstone and sandy conglomerate,the sand bodies are extensively distributed.The Yingcheng Formation is mainly developed braided river delta deposits.(2)The study area mainly experiences 4 structural movements.Embryonic form in study area is formed on the late periods of Huoshiling Formation.The formation of Yingcheng Formation entrapment is owing to the superposition and transformation of two structural movement that include in the structural movement of the late periods of Yingcheng Formation and Denglouku Formation,and the entrapment stereotypy is on the periods of Nenjiang Formation.The fault plays a part in adjustment and control to gas accumulations.(3)Through the deep anatomy of high yield gas reservoir in the study area,and combining source-reservoir-seal with the main controlling factors of reservoir formation sum up the following rules: The Shahezi Formation source rocks and Yingcheng Formation source rocks are the material foundations for forming the gas accumulations of Yingcheng Formation.The big rang of sand-body provided good condition for forming the gas accumulation.The entrapment forming time under the control of structural movement is the necessary condition of forming the gas accumulation.The fault nose,broken block and anticline structure area where is less damaged by the structural movement of the periods of Nenjiang Formation and near source rocks are the favorable areas for gas accumulation.