Methods for Determining Threshold Pressure Gradient of Tight Sandstone
Low-velocity non-Darcy percolation is a common phenomenon when the fluid flow in the tight sandstone,which is often characterized by the threshold pressure gradient.The 2-phase gas-wa-ter experiment is conducted on 4 cores to precisely obtain the value of threshold pressure gradient of oil field in Nanpu.Based on the experiment data,nonlinear percolation feature is shown between gas percolation velocity and pressure gradient.The threshold pressure gradient is calculated by plotting the relationship between gas effective permeability and the inverse of mean pressure as well as gas velocity and difference of pressure square curves.Meanwhile,the numerical model of 4 cores are built to model threshold pressure gradient considering and regardless of the capillary pressure.Re-sults show that the measured value of threshold pressure gradient is greater than the simulated value,and the value considering capillary pressure is greater than the value regardless of capillary pressure.Eventually,we can conclude that the capillary pressure is the foremost factor causing the threshold pressure gradient.
万方数据
维普
