Factors controlling Oiliness of Jurassic Lianggaoshan tight sands in central Sichuan Basin, SW China

Abstract By comprehensively analyzing oil-bearing and non-oil-bearing tight sandstone reservoir properties, pore structure characteristics and contact between source rock and reservoir, reservoir fluorescent photographs of typical wells of Jurassic Lianggaoshan Formation in central Sichuan Basin, the research tries to find out factors controlling the oiliness of the Jurassic Lianggaoshan tight sandstone reservoir. The oiliness of the Jurassic Lianggaoshan tight sandstone reservoir in central Sichuan Basin is controlled by the following factors: (1) The migration pathway between the source rock and reservoir: when there exist sandstone and mudstone transition zones with high mud content and poor physical property between the source rock and reservoir, without fracture connection, it is difficult for oil and gas to migrate into the overlying reservoir; (2) The reservoir physical property: if the reservoir contacts directly with source rock and has good physical properties, oil and gas can migrate and accumulate directly in the reservoir. (3) Development degree of fractures: when the reservoir physical properties are poor, rich fractures can improve porosity and permeability of the reservoir, oil and gas can still migrate and accumulate in the reservoir; if the reservoir physical property is poor and no fractures developed, oil and gas are difficult to migrate and accumulate in the reservoir. Based on the sedimentary and reservoir characteristics of Jurassic Lianggaoshan Formation in central Sichuan Basin and the distribution of source rocks, Yingshan-Guang'an and Hechuan-Baimiao-Luodu two favorable exploration zones are selected.