Review on pore-network modeling studies of gas-condensate flow: Pore structure, mechanisms, and implementations

Gas-condensate flow is a critical process in the near-well region where the well production efficiency is strongly affected by the production of condensate dropout. Pore-scale simulations have provided an understanding of the underlying processes such as snap-off and the effect of the interplay between viscous and capillary forces on gas-condensate flow and its induced blockage within the pore spaces. Among various modeling approaches used to explore these phenomena, pore-network modeling, due to its computational efficiency and the ability to simulate relatively large sample sizes, has appealed to researchers. This article presents a review of the development of pore-network models to simulate gas-condensate flow, particularly in the near wellbore regions. This contribution reviews pore-scale mechanisms that should be included in simulating the gas-condensate flow, together with the involved processes and the peculiarities pertinent to such modeling efforts. After a brief review of different pore scale studies and their differences, advantages, and disadvantages, the review focuses on pore-network modeling, and the application of pore-network modeling in gas-condensate flow in the recent studies. The employed methodologies, highlights, and limitations of each pore network study are examined and critically discussed. The review addresses pore-space evolution, flow mechanisms, and the involved flow and transport parameters. The formulations of capillary entry pressure in different pore geometries, the corresponding conductance terms, snap-off criteria, and conditions for the creation of condensate bridging in different pore structures are presented. Additionally, three major approaches used in pore-network modeling of gas condensation, namely quasi-static, dynamic methods and dynamic compositional pore-network modeling, are presented and their main governing equations are provided using various tables. Finally, the significance of gas-condensate flow modeling including its modeling challenges together with the main similarities and differences among pore-network studies are provided

A Discrete‐Element‐Based Pore‐Scale Hydromechanical Approach to Investigate the Hysteresis Effect on the Unsaturated At‐Rest Earth Pressure Coefficient

ABSTRACT Accurate design of several geotechnical structures, such as retaining walls and piles, necessitates a thorough understanding of the dependence of earth pressure on various soil conditions. Designing resilient earth structures in a rapidly changing climate requires consideration of soil moisture variations caused by droughts or intense rainfall. Therefore, saturation‐dependent alterations in the soil's mechanical behavior, such as lateral earth pressure, are crucial to consider. In this study, a pore scale approach, namely, a coupled discrete element‐pore network method, was utilized to study the volumetric behavior of unsaturated sandy soils under at‐rest conditions. The simulated oedometer tests indicated that the behavior of the soil under study is nonlinear, regardless of variations in the degree of saturation and the hydraulic hysteresis, in which the elastic and elastoplastic regions can be vividly captured. The higher the suction level, the more stretched the elastic region, highlighting the suction‐induced effects on the lateral pressure variation with vertical stress; moreover, the increase in suction results in lower values for the at‐rest earth pressure coefficient. Finally, the effect of the hysteresis phenomenon and cycles of drying–wetting on the at‐rest pressure coefficient was examined. The effect of drying–wetting cycles was assessed in terms of a new quantity, the so‐called degree of hysteresis in K0. The results indicate that the earth pressure coefficient is highly dependent on the hydraulic path as well as the drying–wetting cycles, where a considerable reduction in the degree of hysteresis in K0 was observed during the second cycle of drying–wetting and this reduction is more prominent in the samples of lower density