Shale Gas Occurrence And Seepage Characteristics Research

There is a huge deposit of shale gas resource in the whole world. It is clean, with which the carbon discharge after burned is almost a half of that by coal or petroleum. The shale gas development was started first in America, and it has become the most successful development in the world, while, in China the shale gas is still under exploration, that we still have many pre-works to do. In this paper, fundamental geology characters of shale gas reservoir is studied based on the shale gas samples and geology documents in Sichuan Basin. The occurrence or status of shale gas in formation is studied by focus, and seepage flow in shale is studied by the consideration of effective stress effect. Through the study on shale gas occurrence, geological reserves can be evaluated more precisely. Moreover, by the study of seepage flow in shale media, more reasonable and effective way to develop the shale can be easier to be carried out. First, the fundamental seepage flow space characters of shale gas reservoir in Sichuan Basin are studided. Accumulation mechanism of shale gas reservoir, seepage flow space characters, fracture character, imbibitions ability and wettability are studied based on the shale outcrop samples and core form downhole in Sichuan Basin. Second, based on the Langmuir isothermal adsorption theory, the adsorption characters and the gas occurrence are studied. Theoretical formula to illustrate the relationship among specific surface, pore diameters and adsorption amount are established. In the paper, the pore structure in the matrix is assumed to be balls with the same size, and based on the assuming, the relationship between pore diameters and specific surface, and the relationship between pore diameters and adsorption amount are built up, with which the status of shale gas occurrence can be studied. Through the study, the adsorption gas is more than the free gas when the pore diameter reaches a certain degree. Last, diffusion equation in the shale maaix is solved and used to calculate the flow diffusion rule in the matrix under steady flow conditions. Based on the seepage flow characters of dual media shale, the effective stress is coupled into the dual media seepage flow model, and the seepage flow ability in shale of micropore and microstructure coposition is studied. Through the study, seepage flow ability declined when the effective stress is considered, and there is a smaller influence of seepage flow in matrix than that in the fracture. Based on the study, the determination of drilling and expliotarion methods, and reserves evaluation can be studied theoretically.