Degree of Oil-Gas Charged in Lens-Shaped Sand Body in Jiyang Depression and Its Main Controlling Factors

Lens-shaped sand body oil-gas reservoir is an important kind of lithological oil-gas reservoir. It is widely distributed in Jiyang depression. The statistical data of the degree of oil-gas charged in the lens-shaped sand body (the ratio of the volume of the sand body charged by oil and/or gas to the volume of lens-shaped sand body) in Jiyang depression shows that the degree of oil-gas charged is between 26.8% and 94.1% with an average of 55%. While the degree of oil-gas charged in the overwhelming majority of lens-shaped sand bodies is over 40%, and the degree of most of lens-shaped sand bodies is over 60%. lens-shaped sand body oil-gas reservoir is mainly distributed in the Fourth, the Third and the Second sections of Shahejie Formation. It is found that the degree of oil-gas charged in the Third Section of Shahejie Formation is the highest, averaged at 59%, and the next is in the Second Section with an average of 50%. The degree of oil-gas charged in the Fourth Section is the lowest; its average is only 33%. The primary factor analysis of main controlling factors for the degree of oil-gas charged in the lens-shaped sand bodies suggests that the most important controlling factors are geometry of the lens-shaped sand bodies (thickness and area of the lens-shaped sand body) and the oil-gas migration conditions (the quantity of fault within the lens-shaped sand bodies, the distance between the lens-shaped sand body and source rock and the surplus pressure within the lens-shaped sand bodies). The second important controlling factor is the porosity and permeability of the lens-shaped sand body.