A Research On Tight Sandstone Reservoir Heterogeneity Of He 2-3 Member Of Lower Shihezi Formation In Tabamiao Block

As an unconventional gas reservoir, tight sandstone gas reservoir can efficiently make up thedecreaseof conventional natural gas reserves for its latent huge amount of resources. Thus it hasalready attracted many domestic and overseas scholars'attention and been the research hot andfront question in the development of tight sandstone gas. He 2-3 member of lower ShiheziFormation in Tabamiao area just have the typical characteristics of tight sandstone reservoir, suchas tight lithology, low porosity, low permeability, low –normal pressure , low trap amplitude andlow natural production. Preliminary study has indicated that reservoir heterogeneity is one of themajor causes of production discrepant distribution. Therefore, it is of vital importance for theexploration and development of natural gas to strengthen the study on tight sandstone reservoirheterogeneity in order to find out the inner mechanism and controlling factors. Be aimed at characters of tight sandstone reservoir in He 2-3 member of lower Shiheziformation, Tabamiao area, the study focus on the reservoir heterogeneity. Based on the loggingdata, analysis in lab of core, and well testing data, and by the aid of advanced technology andmethod of computer mapping and statistics, tight sandstone reservoir heterogeneity has beenstudied in the aspects of macro and micro-scale. And further, the formation mechanism andheterogeneity distribution characters of tight sandstone reservoir have been revealed. On the basisof above research, the evaluation parameters of both macro and micro-scale heterogeneity areselected to develop the reservoir multiparametric integrated evaluation so as to discuss further therelationship between reservoir heterogeneity and production anisotropic distribution, which canserve as the exploration and development of gas reservoir. Achievements of the paper are as follows: (1)He 2-3 member of Shihezi formation of Tabamiao block mainly develop braided riversedimentary system, and partly have the character of meandering river, which can be subdividedinto braided river channel, river channel brim and floodplain. The braided river channel sandbodyis the major storage body with characteristics such as great horizontal and vertical variance, greatplane discrepant distribution of lithology, porosity and permeability, high heterogeneity, and soon. The spacial distribution of sedimentary microfacies has dominated the geometry shape ofsandbody and discrepant distribution of lithology, porosity, permeability and production. And thevariance of sedimentary microfacies, lithology and its mineral component, along withheterogeneity of microcosmic pore structure are all the major causes of tight sandstone reservoir. (2)Through the synthetic analysis of vertical and plane heterogeneity of lithology, sandratio and reservoir density in six members of the work area, the order of lithology heterogeneityextent from big to small are as follows: H2-2(2)>H3-2>H2-2(1)>H2-1(2)>H3-1>H2-1(1).And the order of member connectivity is H2-1(1)H2-2(1)>H2-1(2),H3-1>H3-2>H2-2(2).(3)He 2-3 member reservoir have large content of rock debris with average content of26.5%, and mainly develop french grey medium-grained and medium to coarse grain lithic quartzsandstone, french grey medium-grained lithic sandstone, and a small quantity of fine to mediumgrained felspathic lithic sandstone. The pore structure heterogeneity is serious for thedevelopment of secondary dissolved pores, such as intergranular dissolved pore, intragranulardissolved pore, intercrystal micro pore and intercrystal seam, along with middle-thin throat type.And by means of cluster analysis, the pore structure is classified as three major types, of whichType Ⅰhas high quality for its homogeneous pore structure and fine property, Type Ⅱ is thesecondary, and Type Ⅲ is the worse one. The capillary pressure curve of Type Ⅰ reservoirpresents a flat section, coarse skewness, fine sorting, low displacement pressure, bigg...