The Investigation of Threshold Pressure Gradient of Foam Flooding in Porous Media

Porous media were simplified as a series of constricted capillary tubes related to particle size and arrangement, and the distribution of pore diameter and pore volume factor in the pore cell was calculated. Based on mechanics theory, the models of threshold pressure gradient (TPG) for a pore cell and porous media were obtained that provided a comprehensive consideration of pore structure, gas-liquid ratio (GLR), gas liquid interfacial tension, and the deformation characteristics of bubbles in throat and pore. Moreover, the experiments on the TPG of foams at steady state were investigated. The results showed that the TPG decreases sharply as the particle size increases up to 400 mu m and then decreases slightly. The greater the interfacial tension, the higher the TPG, and there exists a approximate linear correlation between them. In addition when the GLR is lower than 20:1, the TPG increases rapidly as the GLR increases, and then the TPG remains almost steady.