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.