煤层气藏产能动态预测方法及参数敏感性分析

煤层气体在开发阶段经历了解吸—扩散—渗流的复杂过程,会引起孔隙结构的变化,对产能造成一定影响。因此,研究煤层气藏的物质平衡时,需要考虑自调节效应对孔隙变化的影响。通过建立模型,推导了煤层气藏的物质平衡方程,结合气、水产能方程以及相渗曲线,并且考虑偏差因子随压力的变化,对煤层气藏产能进行动态预测,预测结果通过与实际生产数据历史拟合,验证了模型具有较高的可靠性。通过参数敏感性分析,得出煤层气井生产中后期不同敏感性条件下储层压力与时间成指数对应关系及其对气井生产的影响。综合分析结果表明,自调节效应好、渗透率高、朗氏压力高和煤层厚度大的煤层气藏产能相对较高。

Study on dynamic prediction method and parameter sensitivity analysis of coalbed methane reservoir production

Coalbed Methane (CBM) gas has a complex process of desorption-diffusion-seepage in the stage of development, causing the changes of pore structure and impaction on production to some extent. Therefore, it is necessary to take the self-regulating effect on pore changes into consideration when studying the material balance of CBM reservoirs. On the basis of the establishment of the model, we infer the CBM reservoir material balance equation. Combined with gas, aquatic energy equation and the relative permeability curves as well as the deviation factor with increasing pressure, we conduct dynamic predict of CBM reservoir production. It is of high reliability by matching the predicted results and the actual production data. Based on the parameter sensitivity analysis,we obtain that in the late production of CBM wells, on the condition of different sensitivity, reservoir pressure and time exhibit an exponential correlation, and the impaction of reservoir pressure on gas well production. Comprehensive analysis of the results showsthat the CBM reservoir production of good self-regulating effect, high permeability, high Langerhans pressure and big seam thickness is relatively high.