复杂岩性储层渗透率-应力敏感性及其对气井产能的影响

采用变流压定围压试验方式,在高温、高压条件下模拟了气藏开发过程,研究了复杂火山岩气藏储层渗透率应力敏感性,对比了变流压定围压与常规的定流压变围压方式评价储层应力敏感性的异同。试验结果表明,火山岩储层渗透率随着孔隙压力的减小而减小,渗透率减小主要发生在孔隙压力从40 MPa下降至25 MPa的变化区间,渗透率损失率与其初始渗透率之间的相关性较差,这与常规沉积砂岩储层具有一定的差别。变流压定围压试验评价的应力敏感性强于定流压变围压评价结果,气藏储层有效应力变化范围内两种试验评价的应力敏感性结果差异更大。基于渗流力学理论,推导得到考虑应力敏感性的气井产能方程。计算结果表明,考虑应力敏感性时气井无阻流量约为不考虑应力敏感性时的63.28%,应力敏感性对气井产能的影响随着生产压差的增大而增大。

Permeability-stress sensitivity of complex lithology reservoir and its effect on gas well productivity

Permeability-stress sensitivity of complex volcanic reservoir has been studied using the variable pore pressure-constant confining pressure method. Meanwhile, permeability stress-sensitivity obtained from two different experimental methods also has been compared. The experimental results indicate that the volcanic reservoir permeability declines with the decrease of reservoir pore pressure. Decrease of reservoir permeability mainly occurs in the pore pressure from 40 MPa to 25 MPa. There is no good relationship between rock initial permeability and its loss rate, which is different from that of the sedimentary sandstone reservoir. Permeability-stress sensitivity of tight volcanic gas reservoir obtained from variable pore pressure-constant confining pressure is much stronger than that obtained from constant pore pressure-variable confining pressure. And this difference becomes larger during the actual gas reservoir effective stress range. The gas well productivity equation has been mathematically derived taking permeability-stress sensitivity into consideration. Numerical results show that the absolute open flow potential(AOF) when considering the permeability-stress sensitivity is about 63.28% of that when the permeability is considered as constant during the gas reservoir production.