Study On Micro - Pore Structure Model And Adsorption Capacity Of Shale Reservoir

With the development of technology, unconventional resource development has made great progress. As one of the most important part of unconventional gas reservoir, shale gas reservoir has received extensive attention. This thesis focuses on the microscopic pore structure and adsorption capacity of shale gas reservoir by theoretical and experimental study.Combined with researches domestic and overseas, this paper takes Longmaxi formation shale from Sichuan Basin as research object. X-ray diffraction, X-ray fluorescence, SEM (Scanning Electron Microscopy), nuclear magnetic resonance, low nitrogen adsorption, high pressure methane adsorption experiments were done to support the research. Through research and analysis, relevant parameters of Longmaxi shale lithology, geochemical characteristics, pore structure and adsorption capacity are yielded, a suitable method for shale indoor core experiments is summarized.With SEM observation, pore structure of Longmaxi formation is classified as inorganic pore and organic pore. The former mainly consists of granular intergranular pore, clay intergranular pore, intracrystaline pore, marginal pore, intragranular dissolved pore and biological pore. The fracture is classified as tectonic tension fracture, structural shear fracture, interlayer lamellation fracture and diagenetic contraction fracture.Pore structure model is established based on fractal theory, and the characteristic parameters of pore structure model is yielded by analyzing shale pore fractal characteristics combined with experimental results. By establishing multi-fractal adsorption model, comparison to Langmuir monolayer adsorption model, BET multilayer adsorption model and D-A model is done to analyze the applicability of each model in shale gas reservoir. At the same time, with the introduction of pseudo-saturated vapor pressure in supercritical pressure adsorption experiments, the wider range of temperature can be applied to BET model and D-A model. With the help of characteristic curve and net adsorption heat, D-A model and BET model can be used to forecast the adsorption isothermal of shale, the relative coefficient is0.99.The adsorption amount of shale is determined by the inner composition and environment. Adsorption capacity of shale is determined by its pore structure and specific surface area, which are affected by the composition of shale, including clay minerals, quartz and organic matter. Temperature, pressure, and moisture content can also affect the adsorption process of shale.