考虑基质水的欠饱和煤层气藏物质平衡方程

Material balance equation considering matrix water in undersaturated coal bed methane reservoir

欠饱和煤层气藏中存在基质水,该类气藏开发过程中的自调节效应会影响基质水的含量,进而影响利用物质平衡方程预测出的地质储量。在分析自调节效应对孔隙度及基质水影响的前提下,推导出考虑基质水情况下的煤层气藏物质平衡方程。通过实例分析得出:考虑基质水时,对预测的吸附气地质储量影响较小,但预测的游离气地质储量明显小于不考虑基质水时的地质储量;随着煤体基质最大收缩系数的增大,预测得到的吸附气和游离气地质储量均呈递减趋势,其中游离气地质储量的递减更为明显。

There is matrix water in the undersaturated coal bed methane reservoir.The self-adjustment effect existing in the process of development of coal bed influences the content of matrix water.And it will affect the geological reserves predicted with material-balance equation.In this paper,the material balance equation for coal bed methane reservoir is derived on the basis of considering the impact of self-adjustment effect on porosity and matrix water.The example analysis shows that the influence on the predicted reserves of adsorbed gas is less than free gas,the predicted reserves of free gas is obviously less than the predicted reserves that matrix water is neglected.It also shows that the predicted reserves of absorbed gas and free gas both decline with the increase of the maximum contraction coefficient of coal matrix.The declination of free gas reserves is more obvious.