Characteristics And Controlling Factors Of T₂l₄³ Reservoir Rocks Of Middle-triassicleikoupo Formation In Longgang Area Of Northeastern Sichuan Basin, China

Research on Middle-Triassic T2l43 reservoir rocks can help to know the characteristics of reservoir controlled by unconformity above Leikoupo formation as well as the effect to upper formation of Leikoupo in other area of Sichuan basin by this unconformity. Combining with logging analysis and reservoir physical property data, this paper studied the characteristics and controlling factors of reservoir rock in Middle-Triassic5s top formation — T2l43 formation in Longgang area of central Sichuan Basin by means of cores, thin section observation, cathodoluminescence,strontium isotope test, carbon and oxygen isotope test. Meanwhile, this paper also briefly discussed the differences of T2l43 reservoir characteristics and controlling factors between different area in Sichuan Basin. The results indicate that the T2l43 reservoir rocks in Longgang area are chiefly composed of gypsum-dissolved breccia dolostone and granular dolostone. Gypsum-dissolved pores, intergranular(intragranular) dissolution pores and intercrystalline dissolution pores are the main reservoir space, reservoir physical property is not good on average. Controlling factors of reservoir are sedimentary facies of evaporative carbonate platform and sedimentation of gypsum, granular carbonate rocks controlled by palaeo geomorphology in the carbonate platform, epigenic karstification and infilling after the tectonic uplift during Indosinian. And in Yuanba area, which is close to Longgang area, has almost the same characteristics. However, in west Sichuan depression and southwest area of Sichuan basin, the effection of epigenic karstification is decreasing.Instead of that, the main controlling factors of these two areas are microbial reefs(beaches) and granular beaches as a result of eustatic movement respectively.