Abstract:

An accurate calculation of lost gas of shale is of great significance for determining total shale gas content, evaluating the potential of shale gas resources and predicting favorable areas.On the basis of a detailed analysis of pressure history and temperature history of the drilling shale core, we use the geological model of lost gas to fix the method of calculating lost gas content and the module of transient thermal analysis of ANSYS to determine the initial moment of lost gas.Based on the above, we propose an improved method of USBM and use an example to verify the reliability.For a certain sample, this study shows lost gas content is positively related to lost time, and the lost time is related to the density of formation water, the density of the drilling mud and the pressure coefficient of formation.For a certain sample, this study also shows lost gas content is also positively related to the initial moment, and the initial moment can reduce the randomness of selecting data points.This improved method has a strong feasibility.Few lost time and low initial moment are the main reasons for little lost gas content of gas shale in Member Chang 7, Ordos Basin.

Key words: lost gas content, lost time, improved method of USBM, Ordos Basin, Member Chang 7