Study On The Characteristics Of Marine Shale Reservoir Development In Southern Sichuan

In southern Sichuan,a large number of organic-rich dark mud shales are distributed,which is one of the important blocks for shale gas exploration and development in China.The paper takes the Lower Cambrian Qiongzhusi Formation and the Lower Silurian Longmaxi Formation shale as the research object,and uses the drilling,logging,core,and analysis data as the basis to analyze the characteristics of the organic matter in the formation and the mineral characteristics,analysis of pore structure characteristics,physical properties,and its relationship with gas-bearing properties,summarizing the influencing factors of the gas-bearing characteristics of marine shale intervals,and conducting in-depth research on shale reservoir development characteristics.The main achievements of the research are as follows:1.The average TOC content of the shale in the Qiongzhusi Formation of the Jinshi-1 well is 0.39%;the average TOC content of the shale in the Jinye 1 well of the Qiongzhusi formation is 0.69%;The average TOC content of the shale in the Longmaxi Formation in the Weiye 1 Well is 1.66%,and the average TOC content in the shale in the Longmaxi Formation in the Yongye 1 Well is 1.89%.The test result of TOC and brittle mineral content shows that the correlation of TOC and DEN in Longmaxi Formation was the highest,while the correlation of TOC and GR in Qiongzhusi Formation was the highest,the strength of diagenesis is the main reason for this difference.When calculating the brittle mineral content with the logging curve,due to the complex composition of brittle minerals,the factors affecting logging are more;2.In the study area,the medium-carbon and medium-silicon rock phases and the rock with higher organic carbon content are favorable rock-facies types,in Longmaxi Formation,the favorable rock phase mainly appears at the bottom,while in the Qiongzhusi Formation it appears at the midle section;3.Development and characterization of quantitative pore consider that organic pore is the main type,and the results show that the organic pore is the main body of the effective reservoir space in the shale reservoir section of the marine facies,with the clay minerals in the hole and the lowest contribution of the brittle mineral hole;4.The porosity of rock samples in the study area is mostly less than 2%,and the overall porosity is small,which is a compact reservoir type.The correlation between porosity and permeability is not obvious,reflecting its poor pore structure and poor connectivity.Organic carbon content has a positive effect on the development of pores,especially micropores;5.The average gas content of the Jinye 1 well in the study area is 0.72m~3/t;the average gas content of the Weiye 1 well is 2.91m~3/t.Overall,the gas content of the Qiongzhusi Formation is low,and the high values of individual gas content occur at the top of the 2nd and 3rd submembers(around 3578m)and the 2nd submember of the 3rd member of the Qiongsan Member(near 3297m);The gas content of the Longmaxi formation is overall higher,and the gas content from the top to the bottom shows an increasing trend,and the gas content at the bottom of the Longmaxi formation can reach about 6m~3/t.Whether in the LongmaxiFormation or in the Qiongzhusi Formation,the content of organic matter is to control the determinants of gas content in size,and with the increase of organic carbon content,the porosity will increase and the gas content increases too.