Lithofacies Characteristics And Petroleum Geological Conditions Of Cretaceous In Jiayin Fault Depression

Jiayin Fault Depression is located in the east of Sunwu-Jiayin Basin,Which is located in Jiayin County,northeast of Yichun City,Heilongjiang Province,with an area of 3656 km~2.It is one first-level tectonic unit of the Sun Wu-Jiayin Basin,which is a Mesozoic-Cenozoic basin.On the basis of 2D seismic data of Jiayin fault depression,combined with the drilling data of Jia D2(JD2)well and field outcrop data,beginning from the geological structure and stratigraphic characteristics of the fault depression,useing the seismic inversion technique based on logging constraints firstly.The Jiayin fault depression was comprehensively studied by the aspects of basic geological conditions;lithofacies development and evolution characteristics,and the geological characteristics of the reservoirs and reservoirs,and the favorable areas were predicted,Reached the following conclusions:It is held that six facies types:fluvial facies,fan delta facies,delta facies,lacustrine facies,explosive facies and effluent facies are developed in Jiayin Drepression,which are further divided into 10 subfacies and 14 microfacies.The volcanic facies developed mainly in Ningyuancun Formation,the fan delta facies developed mainly in Taoqihe Formation,the delta facies developed mainly in Yongancun Formation,the lacustrine facies developed mainly in Taipinglinchang Formation,and the fluvial facies developed mainly in Yuliangzi Formation.On the whole,Jiayin Depression is a volcanic,fan delta-lake,lake-delta,delta-lake-flue sedimentary system,its source supply comes mainly from the eastern and the western in the early stage,and mainly from the west in the later stage,and its sedimentary center gradually expanded from the center to the periphery of the basin.Using log binding seismic inverting technique is used in virtual 2D work area to carry out the inversion.on the basis of Seismic inversion,the results can be listed as following:The thickness of the Taoqihe Formation is about 100m~340m,the thickness of sand body is about 50m~200m,the thickness of mudstone is about20m~150m;the thickness of Yongancun Formation is about 30m~200m,the thickness of sand body is about 20m~120m,the thickness of mudstone is about 20m~150m;the thickness of Taipinglinchang Formation is about 60m~400m,the thickness of sand body is about 20m~100m,and the thickness of mudstone is about 60m~220m.The reservoir property inversion of each target layer show that the study area belongs to the Medium porosity and low permeability reservoir.The organic matter abundance of the source rocks of Taipinglinchang Formation is better,followed by Yongancun Formation and Taoqihe Formation.The kerogen type is mainly type II-III,which is in the stage of mature evolution.The mainly combination types of source-reservoir-seal assemblages are self source rocks and self reservoirs type and lowernsource rocks and upper reservoirs type.And eventually,it is determined that the central part of the Wulaga is the most favorable zone for oil and gas in Jiayin fault depression.