A Research Of Geological Controlling Factors Of Gas Well Productivity In Tight Gas Reservoir

The SuX area is located in the north of Sulige gasfield.The main target strata in this area are He₈ member of Shihezi Formation and Shan1 member of Shanxi Formation.The gas reservoir in Su X area is characterized by low pressure,low porosity,low permeability,low abundance and high water content.Due to the lack of understanding of reservoir characteristics in this area,the productivity of production Wells is irregular.Therefore,it is very important to know the main controlling factors of gas well productivity.Based on the theory of sequence stratigraphy,sedimentology,petroleum geology and reservoir petrology,and based on the analysis of outcrop,core observation,SEM and thin section data,this paper systematically studies the stratigraphic characteristics,macroscopic sedimentary characteristics and microscopic reservoir geological characteristics of the He₈ member of Permian Shihezi Formation and the Shan₁ member of Shanxi Formation in Su X of Sulige area.Combined with production data,dynamic analysis and other contents,the static geological characteristics and dynamic production data are compared.To understand the distribution characteristics of gas and water,discuss the main controlling factors of gas well productivity,and describe the law of gas enrichment.The He8 submember is divided into lower He8 and upper He8,and Shanxi component Shan-1 and Shan-2.It is believed that the lower He-8 member belongs to braided river deposition,and the upper He-8 and Shanxi Formation belong to meandering river deposition.In braided river deposition,channel and central bank are the main reservoirs,and"isolated"channel along the edge bank is distributed in the NWS-SE direction.Lithic quartz sandstone and lithic sandstone are the main rock types in the reservoir,and the main pore type is secondary pore,mainly intergranular dissolved pores,followed by primary residual intergranular pores.The physical properties of the lower member of Box 8 are the best.The reservoir sand body is mainly distributed in narrow strips with poor continuity,strong plane heterogeneity,low effective thickness of a single layer,and multi-stage sand bodies are stacked in the longitudinal direction.In terms of production,the proved geological reserves of Su X area are 1466.04×108m3,the average daily gas production of 95 Wells is 5.68×104m3,and the test gas production is 1.00-4.00×104m3,which is the main production well,and the high production Wells of class I and class II are locally enriched.The western structural point of the block is dominated by low-lying water,while the eastern structural point is dominated by retention water.The accumulation pattern is first accumulation and then compaction,and the macrostructure has no obvious effect on gas-water differentiation.Through the comparison of reservoir geological characteristics and dynamic production data,there is a significant positive correlation between unobstructed flow and porosity,and a positive correlation between accumulated production and effective thickness of sand body.The thickness and grain size of sand body are determined by sedimentary microfacies,and the reservoir and physical properties of reservoir are controlled by diagenesis.The structural conditions directly affect the continuity of sand body,trapping and other conditions conducive to the preservation of natural gas.It is proved that the productivity is affected by diagenesis,sedimentary microfacies,tectonism and other main control factors.Therefore,the effective thickness,physical properties and structural conditions of sand bodies under the influence of sedimentary environment,diagenesis and tectonism control the productivity of gas Wells in the study area.