The Developmental Features And Shale Gas Potential Of Permian Source Rocks In Jiangsu Province

Organic-rich shale is widespread in Permian strata of Jiangsu area,which shows strong material basis for the formation of shale gas.However,the research of shale gas is lagging behind and the exploration degree is relatively low.Then basic data collection,drilling core observation,field sections survey and experimental tests have been conducted to investigate and study the structure and sedimentary background,development and distribution characteristics,geochemical characteristics and reservoir physical characteristics of the dark shales in Jiangsu and its adjacent areas.Finally,the geological characteristics of the source rocks and shale gas enrichment conditions in the study area have been basically examined,the preferred reference standard for favorable areas of shale gas in Jiangsu area was put forward and the favorable areas were selected.Our main understanding and results are as follows:1?The organic-rich shales developed in the Gufeng Formation,Longtan Formation and Dalong Formation in the Lower Yangtze region of Jiangsu Province and Lower Shihezi Formation and the Shanxi Formation in North China region of Jiangsu Province.which are favorable for the formation of shale gas and have good resource potential.2?he Gufeng formation developed basin facies,the thickness of source rocks is 20-50m;the Longtan Formation is dominated by delta facies,and the thickness of the source rocks is 100-300 m;the Dalong formation developed deep water shelf-basin facies and the source rock thickness is generally less than 20 m.The upper Permian Lower Shihezi Formation and the Shanxi formation in the North China formation region of Jiangsu are mainly transitional facies.The thickness of the source rocks of Shanxi formation in the study area is less than 80m,while the Lower Shihezi Formation is more than 100m.3?The organic geochemical analysis shows that the value of TOC in the Longtan and Gufeng formation shales in the lower Yangtze strata is 2.0-6.0%,and the mean value of TOC in the Dalong formation shales is more than 3%.The organic matter of the Gufeng formation is mainly type ?1,the Dalong formation is mainly type ?2 and the Longtan formation is mainly ?2-?.The value of Ro in Permian shales is mostly distributed in 0.7-2%.The Shanxi formation has high content of organic matter,and the value of TOC is generally more than 2%,while The value of TOC in Lower Shihezi Formation is 1%-2%.The organic matter in this area is mainly type III.The value of Ro is 1.5%-2%,which suggests mature to high mature stage.4.X-ray diffraction and scanning electron microscopy results show that the Permian shale pores in the lower Yangtze formation area of Jiangsu are developed,the content of quartz and feldspar is generally 40%to 60%,the clay mineral content is usually less than 50%,which have better shale gas reservoir.and exploitation potential.The pores and fissures of the Permian dark mudstones in the North China formation area of Jiangsu are developed,but the content of brittle minerals is low,which is unfavorable for the later fracturing.5.The assessment criteria of organic-rich shales are put forward,and the favorable blocks of shale gas are selected.By comprehensive researchs,it is believed that the Jiangyin-Wuxi area in southern Jiangsu Province and Haian-Rugao area in northern Jiangsu Province of the Longtan Formation are proposed to be the most favorable exploration areas in the future.