基于生产数据的煤层气井解吸区动态预测模型

Prediction models of dynamic desorption area for CBM well based on production data

准确预测解吸区有助于刻画煤层气储量动用范围,为后期开发方案调整与针对性部署提供参考.基于煤层微元割理系统内物质守恒原理,考虑煤基质内气体解吸向煤割理的供气效应、应力敏感与基质收缩对割理孔隙度的影响以及气水两相流对解吸区压力展布的控制作用,建立适用于(未)压裂煤层气直井的解吸区动态预测模型.研究表明:压裂煤层气井的解吸区扩展形态会逐渐由椭圆形演化为圆形;在相同储层条件下,压裂煤层气井的解吸区范围大于未压裂煤层气井;在相同产气条件下,解吸能力较强的煤层对应的解吸区扩展速度较慢.本研究为煤层气井解吸区准确评价奠定理论基础.

Accurate prediction of desorption area is helpful to depict effective exploitation range of coalbed methane reserves,and provides reference for later development plan adjustment and targeted deployment.Based on the principle of material conservation in micro-element coal cleat system,considering the gas supply effect induced by gas desorption from coal matrix to the cleat system,the influence of stress sensitivity and matrix shrinkage on the cleat porosity,and the control effect of gas-water two-phase flow on the pressure distribution in the desorption area,prediction models of desorption area suitable for(unfractured)CBM(coal bed methane)vertical well were established.The results show that the expansion geometry of desorption area of the fractured CBM well will gradually change from ellipse to circle.Under the same reservoir conditions,desorption area of the fractured CBM well is larger than that of unfractured CBM wells.Under the same production performance,desorption area corresponding to the coal seam with stronger desorption capacity expands slower.This article lays a theoretical foundation for accurate evaluation of desorption area for CBM wells.