THE OIL AND GAS GEOLOGICAL CONDITION OF MARINE STRATA IN THE ZIGUI-WUFENG, THE WESTERN XUEFENG MOUNTAINS AREA

There are four sets of high-quality hydrocarbon source rocks in the Zigui-Wufeng,the western Xuefeng Mountain area,including Doushantuo Formation of Lower Sinian,Shuijingtuo Formation of Lower Cambrian,Wufeng Formation of Upper Ordovician-Longmaxi Formation of Lower Silurian,and Qixia and Maokou formations of Lower Permian.The Content of organic carbon usually being 0.21%～9.77%.But organic carbon of Shuijingtuo Formation of Lower Cambrian is more than 1.99%,the max is 9.77%,which is the best hydrocarbon source rocks.Porosity and permeability of the reservoir rocks,the Hamajing Member of Dengying Formation of Sinian,are relatively higher,average is 8.23%,and 3.66×10^-3μm².Hence the Hamajing Member is the best reservoir in the studied area.Based on the development of the source-reservoir-cap rocks in the Sinian-Middle Triassic marine strata,three assemblages can be divided,of which the lower two assemblages belong to the Lower Marine Assemblage,the other belongs to the Upper Marine Assemblage.The assemblage of Sinian-Shipai Formation of Lower Cambrian is well preserved,and can be divided into two secondary assemblages,i.e.,the combination of lower source rocks with upper reservoir rocks and the combination of lower reservoir rocks with upper source rocks.It is concluded that the dolomite reservoir of Sinian Dengying Formation in assemblageⅠis of certain oil and gas exploration prospects.