Structure Characteristics Of Shale And Its Control On Gas Of Shanxi Formation In Yan-Chang Exploration Area

Shale gas content is of great significance for evaluation of resource potential and prediction of favorable horizons,especially for Shanxi Formation in Yan-Chang petroleum exploration area.In this article,structure characteristics including geochemistry,minerals,physical properities,pore structure and laminae are clarified,the gas content is calculated and the main factors are analyzed,finally,the resources potential and favorable horizons are evaluated and predicted respectively.The article suggests that the mean value of TOC is 1.95%,organic matter is mainly ?,the mean value of Ro is 2.59%,Shanxi Formation shale has huge gas capaicity.The clay and quartz are main mineral compositions,which have the percentage of 54.62% and 39.72%,respectively.The mean value of shale porosity is 3.13% and the permeability is 0.0562×10-3mD.Interparticle micropores and microfracture are mainly distributed,while the organic matter pore are limited,and the mesopore make the most contribution to the total pore volume,while the micropore and mesopore have the most pore specific surface area.Shale gas content in Shanxi Formation is 1.5m3/t on average,and laminae has larger gas content than mudstone.And the gas content is largely influenced by the TOC,Ro,clay and pore diameter.The content of different occurrence state of shale gas between laminae and mudstone is different,laminae often has more free gas and less absorbed gas.By volumetric method,the resources potential calculated by Monte Carlo Simulation suggests that Shanxi Formation has a huge shale gas exploration potential with an expected value of 10983.25×108m3.And based on the lithology-electrical property relationship,the article predicts that laminae is mainly distributed in the bottom of Shan 1 member and the top of Shan 2 member,which are favorable for exploration and exploitation.