Abstract
Accurate understanding and predicting the flow paths of immiscible two-phase flow in rocky porous structures are of critical importance for the evaluation of oil or gas recovery and prediction of rock slides caused by gas-liquid flow. A 2D phase field model was established for compressible air-water two-phase flow in heterogenous porous structures. The dynamic characteristics of air-water two-phase interface and preferential paths in porous structures were simulated. The factors affecting the path selection of two-phase flow in porous structures were analyzed. Transparent physical models of complex porous structures were prepared using 3D printing technology. Tracer dye was used to visually observe the flow characteristics and path selection in air-water two-phase displacement experiments. The experimental observations agree with the numerical results used to validate the accuracy of phase field model. The effects of channel thickness on the air-water two-phase flow behavior and paths in porous structures were also analyzed. The results indicate that thick channels can induce secondary air flow paths due to the increase in flow resistance; consequently, the flow distribution is different from that in narrow channels. This study provides a new reference for quantitatively analyzing multi-phase flow and predicting the preferential paths of immiscible fluids in porous structures.
Highlights
Since the effect of preferential flow will be remarkable in leading the non-equilibrium fluid flow subsurface, accurate knowledge and description the preferential paths and interfacial dynamic of immiscible two-phase flow in rock mass and its influence factors are of great significance for the evaluation of oil or gas recovery[1,2] and predication of roadway rock disasters[3] due to the gas-liquid flow
Most previous studies relied on simplified models that neglected many of the important parameters of porous structures
Advanced imaging technologies have been used in laboratory to characterize the porous structures of rock mass, e.g. microtomography technology (MT) and X-ray CT scanning[11,12,13,14]
Summary
Since the effect of preferential flow will be remarkable in leading the non-equilibrium fluid flow subsurface, accurate knowledge and description the preferential paths and interfacial dynamic of immiscible two-phase flow in rock mass and its influence factors are of great significance for the evaluation of oil or gas recovery[1,2] and predication of roadway rock disasters[3] due to the gas-liquid flow. Few experimental and numerical studies are available for quantitatively and visually elaborating the fundamental processes of preferential flow in real rock structures through the effect of pore morphology and channel size, due to the complexity and heterogeneity of porous structures of natural rocks. Liu et al.[23] used the X-ray microcomputed tomography to visualize the multiphase glow during core flooding experiments, and investigated the influence of phase morphology on relative permeability Such laboratory methods are widely used in the simulation of two-phase flow in porous structures. Schiedung et al.[44] proposed a combined computational approach based on the multiphase field and the LBM for the simulation of capillary-driven kinetics These last numerical studies investigated two-phase flow in different perspectives, these models assumed that perfect channel thickness is much smaller than the channel width without considering channel size effects. This study presents an efficient numerical method for predicting the preferential paths in porous media and provides a new research reference for studying multiphase flow in rock structures
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