Abstract:

Adsorbed gas content under the condition of the reservoir temperature and pressure is of great significance for shale gas resource evaluation and target area selection. Therefore, it is necessary to obtain the shale adsorbed gas content and its transformation law under the double variable factors of the reservoir temperature and pressure. By reasonable utilization of isothermal adsorption experiment data under different temperatures, the temperature and pressure double variable factors turn into the single factor of burial depth. We choose one sample A do the isothermal adsorption experiment under different temperatures, rational utilization of different temperature points and experimental pressure, to finish the conversion between temperature, pressure and buried depth through the parameters of temperature gradient, pressure coefficient. Further predicting the corresponding adsorbed gas content of other temperature points, so as to build the adsorbed quantitative prediction model with the burial depth. We use the model to calculate the adsorbed gas content of untested temperature, and the result is relatively accurate. The model is seen as a new reliable method to calculate adsorbed gas content. The research shows that the adsorbed gas content increases first and then decreases with the burial depth increases, and there exists a depth turning point. Above the depth turning point, pressure has more important effect on adsorbed gas content than temperature, and below the depth turning point, temperature has more important influence than pressure. The method makes the best of the experimental data, reflecting the adsorbed gas content transformation law directly, and it has an important guiding significance for resource evaluation.

Key words: isothermal adsorption, adsorbed gas content, temperature, pressure, burial depth, prediction model