改进煤层压后压降的渗透率计算方法

CALCULATING METHOD OF THE PERMEABILITY BASED ON THE IMPROVED PRESSURE DROP AFTER THE COAL SEAM FRACTURED

压后压降测试分析是目前获取煤层渗透率的有效方法。通过对压裂停泵后压降测试数据进行分析,在Nolte经典模型基础上,结合裂缝闭合后压力分析的线性流和径向流数学模型,运用Horner法产量等效原则及Duhamel叠加原理,创建了储层渗透率的计算方法。并利用逐步最小二乘法,实现井底压力的自动拟合,提高了储层渗透率的求取准确性和效率。新疆煤层气井的实例计算说明了该方法的准确性和可靠性,并证实了XX区块渗透率较高、物性较好,具有较大的开发价值。

The analysis of the pressure drop test after the fracturing is the main method to obtain the permeability of the coal seam. Based on the analysis of the pressure drop tested data after stopping the fracturing pumps and classical Nolte model,integrated with the linear and radial flow mathematical models of the pressure analysis after the fracture closure,with the help of the production equivalent principle by Horner method and Duhamel superposition principle,the calculating method of the reservoir permeability is initiated. At the same time,by the gradually least square method,the automatic match of the bottom-hole pressure is realized,thus the accuracy and efficiency of the reservoir permeability are improved. The calculation case history in Xinjiang CBM well proves the accuracy and reliability of this method,and moreover the facts of much higher permeability and pretty better physical properties for Block XX are confirmed,so much greater development value of the block is shown.