Experimental Study On The Characteristics Of Acoustic, Gas Adsorption And Seepage Flow Of Shale In Jiaoshiba

Shale gas is a kind of unconventional natural gas, which mainly exists in the shale layer with adsorption and free state. Shale gas in the United States and other countries the successful exploitation of shale gas is more and more attention by countries around the world. China has the world’s first shale gas reserves, so the prospect of shale gas exploitation is huge. In the next period of time,shale gas will become a very important natural gas resource to ease the energy crisis in our country. Because of the difference of the physical properties of shale in different areas, it is necessary to do further research on the physical properties of the shale.Shale gas reserves in the Fuling, Sichuan basin is rich in shale gas reserves, is the first in China to have industrial shale gas production capacity.In this study, the research object of a outcrop shale in the Sichuan basin is studied. The acoustic characteristics of shale were studied by the method of measuring the P-wave velocity in shale; The gas adsorption characteristics of shale were measured by static volumetric method, and the factors affecting the adsorption of shale were investigated and the influence factors; The pore structure of shale was analyzed and tested, and the Darcy’s law of gas in shale was studied by means of experiment.The results show that the p-wave velocity in shale is mainly affected by temperature, axial pressure, water content and gas saturation. The higher the temperature, the smaller the p-wave velocity; The higher the axial pressure, the greater the p-wave velocity; The higher the water content, the greater the p-wave velocity; The greater the gas saturation, the greater the p-wave velocity.The gas adsorption capacity of shale is influenced by pressure, temperature, size of shale, water content, gas species and total organic carbon. Under the isothermal condition, with the increase of pressure, the adsorption capacity of the gas increases first and then tends to be stable; The gas adsorption capacity decreases with the increase of temperature; The smaller the size of shale,the greater the gas adsorption capacity; The higher the water content, the smaller the gas adsorption capacity; The adsorption of nitrogen, methane and carbon dioxide in shale is increased in turn; The adsorption and desorption of the three gases in shale lag behind, and carbon dioxide lags the most; The higher the total organic carbon, the greater the gas adsorption capacity of shale.In the shale, the main pore size is smaller than 50 nm. Pore structure is divided into: intergranular pore, intragranular pore, organic matter pore and fracture. The apparent permeability of methane, carbon dioxide and nitrogen in shale decreased with the increase of gas permeation pressure, that the slippage effect exists; Under the same permeation pressure, the apparent permeability rank is CO2>CH4>N2; The absolute permeability of the gas in the shale after the slip correction is KN2=0.274 mD, KCH4 =0.182 mD, KCO2 =0.165mD; The greater the confining pressure is, the smaller the apparent permeability; The shale has a certain plasticity.