一种改进的页岩气损失气含量估算方法

页岩气损失气含量的准确估算对于页岩气总气量的确定、页岩气资源潜力评价和有利区预测有着重要的意义。在厘定页岩气现场解析过程中岩心压力史和温度 史的基础上，利用损失气逸散地质模型修正了损失时间的计算方法，利用ANSYS软件瞬态热分析模块确定了损失气量恢复时的初始时刻，进而提出了改进的USBM法，通过实例分析验证了该方法的可靠性。 研究认为：对固定的解析样品，损失气量与损失时间呈正相关关系，损失时间受地层水密度、钻井泥浆的密度和地层压力系数的综合影响；对固定的解析样品进行损失气量恢复时，损失气量与初始时刻 也呈正相关关系，利用ANSYS软件确定的初始时刻可以有效地减少最初不稳定数据点舍去的人为性；改进的USBM法具有较强的可行性，损失时间偏小和初始时刻偏低是造成对鄂尔多斯盆地东南部长7段页 岩样品利用USBM法估算的损失气量偏小的主要原因。

An Improved Method of Calculating Lost Gas Content of Shale Gas

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.