Abstract:

Gas shales are important unconventional gas reservoirs in which much of the gas is stored in the adsorbed state.The amount of shale adsorbed gas is not only a key parameter of shale gas resource evaluation and target area selection,but also an important standard to evaluate the economic mining value of shale.In order to study the main controlling factors of adsorbed gas content of the Fifth Member of Xujiahe Formation from Well Xinye HF-1 in the western Sichuan Depression,we do the isothermal adsorption experiment to obtain the curve of shale adsorption and the parameters of Langmuir volume and Langmuir pressure.We discuss the influence of pressure on shale adsorbed gas and use the Langmuir model to calculate the amount of shale adsorbed gas under formation pressure conditions. In the Fifth Member of Xujiahe Formation from Well Xinye HF-1 in the western Sichuan Depression,shale adsorbed gas content may be influenced by various factors such as specific surface area,porosity,density,maturity,humidity of shale and pressure.Based on the experimental data,we performed a correlative analysis of factors that may influence shale adsorbed gas content.Correlation and principal component analysis were adopted to obtain the main controlling factors including specific surface area, humidity of shale and pressure. Finally,we establish a new model to calculate the amount of shale adsorbed gas as considering specific surface area, humidity of shale,pressure.The new model has a potential ability to calculate the amount of the unknown shale adsorbed gas and the calculation result is found to be in consistent with the experimental data,so it is accurate and reliable.This study is a good method for evaluation of shale adsorbed gas content under isothermal condition,which has a certain guiding significance.

Key words: Well Xinye HF-1, adsorbed gas content, pressure, specific surface area, main controlling factor, new model