CHARACTERISTICS AND TYPES OF MIDDLE-TRIASSIC RESERVOIR IN CENTRALSICHUAN BASIN

The lithological characteristic,reservoir space types,physical features,reservoir types and their formationmechanisms of middle Triassic reservoir rocks in central Sichuan basin are studied through massive coreobservation,thin section analysis and geochemical testing. The middle Triassic reservoir can be divided into threetypes,which are weathering karst reservoir,bank-facies dolomite reservoir and hydrothermal dolomite reservoir.This paper analyzes that the most advantageous district of karst reservoir rock of the east of Moxi and the west ofLongnusi,which is influenced by tectonic uplifting and late diagenesis. The bank-facies dolomite reservoir rockis mainly located in the base of Leikoupo Formation (T2l11),which was mainly developed in Moxi gasfield. Thereservoir rocks are chiefly diverse grain dolostone. Intercrystal pores and solution pores are their main reservoir space.The reservoir is the medium porosity and low permeability,controlled by facies and diagenesis. Hydrothermalminerals are pervasive in the studied area,which implies that there may be reservoir rock related to hydrothermaldolostone in the central Sichuan Basin.