全油气系统源储侧接式致密油藏主控因素及成藏模式OA

The southern slope of the Mahu Sag is a critical replacement area for unconventional oil and gas exploration in the Junggar Basin.Based on data from well logging,core analysis,laboratory tests,and production tests in the study area,research was conducted on the main controlling factors and accu-mulation model of tight oil reservoirs in the second member of the Fengcheng Formation(P1f2)in the southern slope area,according to reservoir types and distribution patterns.The results indicate that the P1f2 reservoirs in the southern slope are tight oil accumulations within a total petroleum system,charac-terized by lateral source-reservoir juxtaposition,overall oil-bearing potential,and local enrichment.Sweet spots are primarily distributed in the second sub-layer(P1f2 2-2)and the third sub-layer(P1f22-3)of the second member interval of P1f2.The reservoirs are jointly controlled by reservoir quality,source rock thickness,and abnormal pressure.Reservoir quality governs the degree of hydrocarbon enrich-ment.Based on pore-throat structure,the reservoirs can be classified into three categories,with class Ⅰreservoirs having coarser grain size and better pore-throat structure,serving as the preferred areas for hydrocarbon enrichment.In the thick-reservoir and thin-source assemblage,the development of thin-layer source rocks not only provides the material basis for reservoir formation but also facilitates accu-mulation by altering reservoir wettability or generating microfractures through hydrocarbon-generation pressurization.Abnormal high pressure controls the spatial distribution of oil-bearing potential and pro-ductivity,with overpressured zones exhibiting higher oil saturation and productivity in horizontal wells.The accumulation model in the study area is defined as lateral source-reservoir juxtaposition,high-quali-ty reservoirs controlling enrichment,and overpressure-driven charging.These findings provide guidance for subsequent development and production in the study area.