The Research Of Sedimentary Facies And Genetic Types Of Reservoir Sand-body Of Xujiahe Formation In Weidong-Anyue Zone

There is a tremendous potential for exploration & development in Xujiahe Formation of Sichuan foreland basin. While, after a long term exploration which only emphasized Maokou Formation in Permian and Jialingjiang Formation in Trias, Xujiahe Formation has been neglected. So, Weidong-Anyue area(research area) becomes the only region in Shunan zone where with biggish area, lower exploration, good hydrocarbon source and preservation, and many pay zones.Taking the basic theories and methods of Preservation Sedimentology and Petroleum Geology as a direction, through comprehensive analysis of the field section, slices, cores, well logs and other information, the sedimentary microfacies types, characteristics and evolvement process of Xujiahe Formation have been detailedly researched. The lake and delta facies are the main types in research area, the delta and shallow-lake bar consist the framework sand-body. On the basis of contrastive research of sedimentary facies, the strata of research area can be divided into six members, the 1st, 3rd and 5th member correspondingly enrich mudstone, while the 2nd, 4th and 6th member correspondingly enrich sandstone, which are the main reservoir.By the characteristic of Xujiahe Formation of research area, on the basis of detailed research of sedimentary facies and lithofacies paleogeography, two sedimentary models were set up: the lake and the lake-delta sedimentary model. The lake sedimentary model were applied for the 1st, 3rd and 5th member of Xujiahe Formation, and the lake-delta sedimentary model were suited for the 2nd, 4th and 6th member.The physical and lithological characteristics of research area have been comprehensively researched. The reservoir condition of Xujiahe Formation in research area is bad, with low or lower porosity and permeability. Compared among 2nd, 4th and 6th member of Xujiahe Formation, the reservoir condition become more and more worse from 2nd to 6th. Reservoir sand-body are mainly developed in 2nd, 4th and 6th member of Xujiahe Formation, and the genetic types of them are distribution channel underwater distribution channel, estuary bar and shallow lake bar and the combination of them. The clastic composition and genetic type of reservoir sand-body have distinct influence to reservoir, they are the basis of reservoir. Compared with the genetic types of reservoir sand-body, the under-water distribution channel and shallow-lake bar sand-body have better reservoir condition than the distribution channel and estuary bar sand-body. For the development of reservoir, The shap corrosion of feldspar is one of the most constructive diagenesis, and the pore lining and grain coating of chlorite play an important role in protection of porosity. But in all, the reservoir condition of Xujiahe Formation in research area is bad, the reservoir conditions strongly sponge on structure cracks which are caused by tectonic movement.The distribution regulations of reservoir and its properties have been ascertained, and the favourable area of every member of Xujiahe Formation were forecasted through comprehensive study of sedimentary facies/microfacies, lithofacies palaeogeography, genetic types of reservoir sand-body, and reservoir conditions.