Study on reservoir characteristics of He8 tight gas reservoir in Yanchang east area of Yan'an Gasfield
In order to deepen the geological understanding of the tight gas reservoir in Yanchang East Area,Yan'an Gas field,the petrology,physical properties and pore structure characteristics of the He8 reservoir in the study area were studied,and the main controlling factors of physical properties were analyzed.The results show that:1)The type of sandstone is mainly lithic quartz sandstone,the clastic component is mainly quartz,and the clay minerals are mainly chlorite and illite.The brittleness index and composition maturity are higher,the porosity and permeability show a strong exponential positive correlation and asymmetric bimodal distribution,and the permeability was mainly controlled by macro pores.The mean porosity and permeability were 5.3％and 0.101×10-3 μm2 respectively,and the lower limit of effective physical property was 2.3％porosity and 0.035×10-3 μm2 permeability,the permeability was mainly controlled by macro pores.2)The average throat radius was 0.41 μm,and the average pore radius was 135.38 μm.The loss of primary pore space is large,and pore radius,effective pore volume and pore-throat ratio are the main controlling factors of reservoir space,and effective throat volume was the main controlling factor of seepage capacity.The pore structure of reservoir can be divided into Ⅰ high quality reservoir,Ⅱ general reservoir and Ⅲpoor reservoir.3)Reservoir physical properties were mainly controlled by strong compaction,weak cementation and weak dissolution.The initial porosity is 38.61％,the apparent compaction rate is 71.83％,the porosity reduced by compaction is 26.44％,the apparent cementation rate is 24.50％,the porosity reduced by cementation is 9.02％,the apparent dissolution rate is 9.48％,and the porosity increased by dissolution is 3.49％.The research results can provide some geological basis for efficient exploration and development of tight gas reservoirs in the study area and even Yan'an Gasfield.
reservoir characteristicsHe8 reservoir grouptight gas reservoirYan'an GasfieldOrdos Basin
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