Controlling Factors Of Chang 6 Tight Oil Accumulation In The Central Oil Area Of Yanchang Oilfield

Guoqi zhaizigou area is located in the Middle East of Northern Shaanxi Slope of Ordos Basin.The main oil layer is Triassic Yanchang 6 oil layer group.With the deepening of development and the continuous increase of recovery degree,the understanding of sedimentation and reservoir can not provide favorable support for exploring the reservoir characteristics of this area.In this paper,the chang-61 and chang-64 reservoirs of Chang-6reservoir in Guoqi zhaizigou area,the central oil area of Yanchang oilfield,are taken as the research object.Combined with the regional geological situation,the distribution characteristics and control factors of the reservoir are deeply studied by making full use of the drilling,logging,logging and experimental analysis data,in order to provide a favorable geological basis for the next development.Carry out stratigraphic correlation division according to the existing data,and determine the sand body correlation standard(auxiliary)layer;Summarize the types of sedimentary microfacies and the development characteristics of sedimentary facies;Study and evaluate the rock type,reservoir type,pore structure,reservoir physical properties and heterogeneity of the reservoir;Analyze and study the "four property relationship" of reservoir,and clarify the distribution characteristics of Chang 61 and Chang 64 reservoirs;Combined with the basic geological characteristics,the control factors of Chang 6 reservoir are summarized and analyzed.The results show that the Chang 6 structure in the study area is a gentle monocline as a whole,the direction is from east to west,and the local part is a low amplitude nose structure uplift formed by differential compaction.Chang 61 and Chang 64 belong to delta front deposits,and the developed microfacies are mainly underwater distributary channel and inter distributary Bay,in which the underwater distributary channel is the framework sand body of delta front.The reservoir lithology is medium and fine-grained quartz sandstone,with poor pore throat sorting,coarse skewness,uneven distribution of pore throat,poor physical properties and strong heterogeneity.It belongs to low porosity and low permeability reservoir.Chang 61 and Chang 64 in the study area are lithologic structural tight reservoirs with rich oil.Sedimentary facies affect reservoir development,provide favorable places for oil and gas accumulation and control reservoir distribution;In terms of the stacking style of sand bodies,the vertical stacking style of cut stack and alternative sand bodies and the plane contact style of butt joint,side cut and alternative sand bodies provide reservoir conditions for the reservoir and control the reservoir scale;Reservoir development characteristics affect the reservoir by controlling the oil-bearing degree of sand layer;The configuration relationship between reservoir and caprock determines the reservoir.The nose structure will affect the oil-water distribution to a certain extent,while the reservoir physical properties have a weak impact on the reservoir.