CHARACTERISTICS OF OIL-BEARING DOLOMITE RESERVOIR IN MID-DLE JURASSIC BUQU FORMATION,SOUTH QIANGTANG DEPRESSION
Based on the dolomite outcrop and core samples from the Middle Jurassic Buqu Formation in the South Qiangtang Depression,this study investigates petrology,porosity,permeability characteristics,fluid inclusions,and diagenesis to elucidate unclear reservoir characteristics.The key findings are as fol-lows:1)Dolomite Types:The Buqu Formation exhibits at least five types of dolomites,including pow-dery,fine,medium,coarse,and unequal crystalline dolomites.2)Porosity and Permeability:Well-devel-oped pores and fractures characterize the formation,indicating it as a medium porosity and medium perme-ability reservoir.3)Fluid Inclusions:Oil and gas inclusions primarily occur in two stages,distributed within dolomites,calcite,and late-filled calcite veins.During the early stage,oil and gas inclusions are mainly found in powdery and fine crystalline dolomites with medium maturity and blue-green fluorescence.Homogenization temperatures range from 45 to 75 ℃.In the late stage,these inclusions are present in medium and coarse crystalline dolomites with high maturity and blue fluorescence,with homogenization temperatures of 105 to 120 ℃.Some inclusions exhibit abnormally high temperatures,suggesting poten-tial thermal event influence during the charging process.4)Diagenesis:Significant diagenesis processes in-clude compaction,pressure dissolution,fracture,dissolution,and metasomatism.The relationship be-tween diagenesis and oil and gas charging involves fine and powdery dolomite,followed by oil and gas fill-ing,saddle-shaped dolomite formation or dolomite enlargement at pore edges,and subsequent oil and gas filling,fissure filling,calcite filling,and residual asphalt formation.This comprehensive study on the res-ervoir characteristics of the Middle Jurassic Buqu Formation in the South Qiangtang Depression holds guid-ing significance and practical value for future oil and gas exploration efforts in the area.
万方数据
维普
