Abstract:

Abstract:Based on a detailed comparative study on reservoir petrology and fluid flow characteristics of waterrock between paleohigh and slope in the Sichuan Basin,the author characterized the features of the Ordovician reservoir and its major controlling factors by using petrographic and geochemical methods,and discussed the exploration potential of the Ordovician in the study area from the perspective of hydrocarbon accumulation.The matrix of the Ordovician reservoir is relatively tight.The reservoir spaces in central Sichuan Basin are dominated by intragranular dissolution pores,intergranular dissolution pores and intercrystalline pores,while that in southwestern Sichuan Basin are dominated by intercrystalline pores and mircofractures.Reservoir development is significantly controlled by the initial sedimentary environment,paleokarstification,oil charging and cracking,and fracturing.The sealing conditions were relatively good during oil and gas generation,leading to the formation of paleooil/gas pools which were completely destructed later due to the uplifting since the YanshanianHimalayan period.Shallow shoal limy or dolomitic grainstone occur in the Honghuayuan and Nanjinguan Formations in southern and eastern Sichuan Basin,and are potential highquality reservoirs.In addition,the gas from cracking of oil in the paleo oil pools in the Sinian and Cambrian is an important gas sources for the gas accumulation in overlying Ordovician.Therefore,the southern and eastern Sichuan Basin may be the most favorable areas for oil and gas exploration in the Ordovician.