Abstract: The theoretical absorption gas amount in shale is an important index to judge whether shale has economic exploitation value. It is significant for shale gas-bearing property evaluation to study isothermal adsorption features of shale and calculate shale adsorption capacity. In order to find the isothermal adsorption features of Chang 7 shale in Ordos Basin, eight shale samples of Chang 7 were selected to carry out high temperature and high pressure methane isothermal adsorption experiments, then the adsorption gas content and adsorption heat were calculated according to the isothermal adsorption characteristic curves, and its influencing factors were analyzed. The results show that the isothermal adsorption of the eight samples from Chang 7 shale is in accord with Langmuir adsorption theory. The theoretical adsorption gas content of the eight shale samples is 0.57-4.35 m3/t, with an average value of 1.98 m3/t. The adsorption heat of Chang 7 shale samples is 10.67-37.67 kJ/mol, the average value is 21.73 kJ/mol, therefore, its adsorption type is physical adsorption. The shale adsorption gas content is mainly affected by specific surface area, TOC content and clay mineral content, among which the specific surface area is the most direct influencing factor. Key words： nonmarine shale； adsorption features； influencing factors； Chang 7 oil reservoir set； Ordos Basin

Key words:  grey system, unbiased optimization model, power function method, metabolism method, production prediction