| Based on the observation of cores and the analyses of logging,organic geochemistry,mineral component,porosity and permeability data of Chang Ye Well No.1(one of the Parameter Well for shale gas in Meishan Area,Changxin,Zhejiang),the sequence stratigraphy framework of Longtan Formation is built up;sedimentary facies,organic geochemical characteristics,petrological and mineralogical characteristics and gas-bearing properties are analyzed;the controlling factors of shale gas accumulation are discussed;and then find out targets for shale gas exploring.According to sedimentology and sequence stratigraphy,3 third order sequences are divided:the upper(L1),the middle(L2)and the lower(L3)member of Longtan Formation.Each member of Longtan Formation develops different sedimentary facies,which are neritic facies,littoral facies and delta facies.Through studying the organic carbon content(TOC),the vitrinite reflectance(Ro),the elemental and maceral composition of kerogen and the rock pyrolysis parameters,it is thought that the shale of Longtan Formation in Meishan Area has high TOC(which rangs from 0.5%to 2%)in the mature stage with Ro values of 0.5%-1.3%,and that most of the organic matters belong to the Type ?B and Type ?.Through the analysis of rock mineral composition,porosity and permeability,it is known that the shale mainly composed of clay and quartz,and the clay mineral concentration is more than 50%.The porosity and permeability of the rocks are very low,but the microporositis and the micro fractures are well-developed.Based on the research of gas-bearing properties of shale,the controlling factors of shale gas accumulation in Meishan Area are found out.They are TOC,Ro,kerogen type,mineral composition,porosity,permeability,shale thickness,buried depth,etc.And then according to influence degree of each facter,4 favorable layers for shale gas are divided.the lower member of L1 and the middle member of L3 will be the targets for shale gas exploring in Meishan Area. |
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