欠饱和煤层气藏的生产动态预测方法

将煤层气藏的物质平衡方程和产能方程相结合可建立生产动态预测方法，但目前人们没有考虑原始煤层的吸附饱和度，所建立的动态储量评价和生产动态预测方法仅适用于饱和或超饱和的煤层气藏。在考虑吸附饱和度的基础上重新推导物质平衡方程，然后建立了生产动态预测方法，使得该法可用于欠饱和的煤层气藏。通过验证表明，当煤层气井处于排水降压期时，该法预测的日产水量平均相对误差为8%，当煤层气井进入产气期时，该法预测的日产气量平均误差为–13%，基本满足工程应用的精度要求。

Production Performance Prediction Method for UndersaturatedCBM Reservoirs

The prediction method for CBM reservoir production performance could be developed by combining the materialbalance equation and productivity equation. When this method was developed by previous researchers，the initial adsorbingsaturation of CBM reservoir is neglected，making the previous method applicable to only the saturated or supersaturated CBMreservoir. In this paper，the material balance equation is re-derived by taking initial adsorbing saturation into consideration，and then the production predicting method was established，applicable to under-statured CBM reservoir. It is demonstratedthat during water drainage period，this method can predict water rate with an average relative error of 8%，and then duringgas production period，it can predict gas rate with an error of –13%，which can meet the accuracy requirement of productionengineering.