Theoretical Study of the Gas Slippage Effect in the Pore Space of Tight Sandstones in the Presence of a Water Phase

Abstract

Compared with the pore throat radius in tight sandstones, the mean free path of a molecule can no longer be neglected. As a result, the gas slippage effect (the Klinkenberg effect) in tight sandstones is quite significant and must be taken into account. The goal of this work was to use an analytical expression to show the effect of pore space structural parameters and temperature on the gas slippage factor, taking into account water saturation in tight sandstones. The mathematical model including water saturation was derived from fractal theory. The calculations of the gas slippage factor (the Klinkenberg constant) using the proposed model agree well with experimental data presented in the literature. We have also studied the effect of pore space structural parameters and temperature on the gas slippage factor for different water saturation values. The gas slippage factor correlates with the tortuosity fractal dimension of the pore channels for high water saturation. This distinguishes the analytical model obtained from the single-phase model neglecting the effect of water saturation.Compared with the pore throat radius in tight sandstones, the mean free path of a molecule can no longer be negligible and so in tight sandstones, the gas slippage effect must be taken into account. Therefore, the process of gas flow through tight sandstones has attracted attention in planning gas field development [1][2][3][4][5]. It has been proven that the mean free path of a gas molecule is on the same order of