Comparison of Deeply Buried and High-Quality Reef-Bank Facies Reservoirs of Puguang Gas Field in the Northeast of Sichuan Basin with Tazhong Gas Fields of Tarim Basin

In recent years,deeply buried and high quality reef-bank facies reservoirs have been discovered in the Changxing and Feixianguan Formation in the northeast of Sichuan Basin and the Lianglitage Formation of Tazhong area in the Tarim Basin has brought the hope for the oil-gas exploration in deep marine facies carbonate strata.Although this reef beach body distribution range is broad,the reservoir quality is good,the proving oil gas reserves are big,but these two basin's reef beach body reservoir actually has the big difference.The reservoir thick of the reef-bank facies reservoir in the northeast of Sichuan Basin is bigger,the porosity and permeability is better than the reservoir of Tazhong,and the lithologic character of the former is dolomite,the latter is limestone.The comparison research of the two areas discovered that the difference is controlled in the following factors:The high energy sedimentary environment and eustatic sea level change have the decisive control on the thickness and poroperm capability of reservoir;the gypsum can affect the dolomite occurrence to a certain extent,improve the poroperm capability of reservoir;the hydrocarbon charge time,the reservoir burial evolution,as well as hydrocarbon-fluid-rock interaction and so on have obvious control on the formation and preservation of the secondary pore,hole and fracture.Because in the northeast of Sichuan Basin when the reef-bank body is growing,the eustatic sea level change is comparatively steady and the water energy is very high,are advantages to grow thick and clean reef-flat body;dolomite is more,recrystallization is common;hydrocarbon is early charge,the reservoir fast bury deeply at the front and in uplift at last,these are advantages to grow the second porosity,so the storage quality of reef-bank reservoir in the northeast of Sichuan Basin is better than Tazhong area.