多因素影响下煤层气井生产初期合理排水量确定

生产初期排水量合理与否影响煤层气井整个生产过程中的排水采气效果,无因次含气率为0.25时,认为排水初期阶段结束。为确定新投产煤层气井生产初期合理排水量,建立考虑压敏效应、基质收缩和煤粉剥离、堵塞效应对煤储层物性的影响模型,研究生产初期不同排水量对煤储层物性的影响;并编制了新投产煤层气井合理排水量确定软件。研究结果表明:生产初期结束时的煤储层孔隙度和渗透率随着排水量的加大先增大后减小,峰值处对应的排水量确定为合理排水量。利用该软件确定了某煤层气井排采初期的合理排水量,结合数值模拟结果分析在该排水量控制下该煤层气井的排采效果较好,该模型对新投产井生产初期合理排水量的确定提供理论依据。

Reasonable discharge rate of CBM well in initial production stage under the influence of many factors

To determine the reasonable discharge rate of CBM well in initial production stage, the dynamic permeability model of coal seam is established considering the effect of effective stress, coal matrix shrinkage and migration of pulverized coal. Analyzing the critical flow of fluids suspending coal fines rate in CBM well, minimum discharge rate are determined. During the coal bed methane production, when the discharge rate is higher than the minimum critical discharge rate in favor of the pulverized coal output, the coal bed reservoir permeability rebounds. As the discharge rate increases, the coal reservoir permeability increases first, then decreases at the end of the initial production stage and the reasonable discharge rate is at the peak permeability. Using this mathematical model the reasonable discharge rate of CBM well in initial production stage is achieved.