煤层气开采过程中渗透率模型比较研究

为了得到煤层气开采过程中渗透率的准确预测模型，分析了不同泊松比和孔隙压力下的储层孔隙率变化规律，通过理论分析对4种经典渗透率模型进行了比较研究。研究结果表明: P&M模型和C&B模型对泊松比敏感度较小，改进P&M模型和S&D模型对泊松比敏感度较大；改进P&M模型能有效反映渗透率变化趋势，在p＜1.4 MPa和p＞4.1 MPa时k/k0数值拟合度较高；P&M模型和S&D模型不能准确描述p＜1.4 MPa时k/k0变化情况，而在p＞1.4MPa时k/k0数值拟合度较高；煤层渗透率随孔隙压力增大表现为“U”型趋势，包含低孔隙压力骤减区、中孔隙压力稳定区和高孔隙压力稳步升高区3个阶段，改进P&M和S&D模型更能表现煤层气渗透率随孔隙压力变化趋势。

Comparative study on permeability models in coalbed methane exploitation

In order to obtain an accurate prediction model of permeability in the exploitation process of coalbed methane, the change laws of reservoir porosity under different Poisson's ratios and pore pressures were studied, and four classical permeability models were compared by the theoretical analysis. The results showed that the P&M model and C&B model were less sensitive to the Poisson's ratio, while the improved P&M and S&D model were more sensitive to the Poisson's ratio. The improved P&M model could effectively reflect the change trend of permeability, and the k/k0 numerical fitness were higher when p<1.4 MPa and p>4.1 MPa. The P&M model and S&D model could not accurately describe the change of k/k0 when p<1.4 MPa, however, the k/k0 numerical fitness was higher when p>1.4 MPa. The permeability of coal seam presented an “U” shape trend with the increase of pore pressure, including three stages of low pore pressure sharp reduction zone, medium pore pressure stability zone and high pore pressure steady rise zone. The improved P&M model and S&D model were more able to express the change trend of coalbed methane permeability with pore pressure.