An Experimental Study of Single-Phase and Two-Phase Fluid Flow in Horizontal Wells

Compressed air energy storage in porous media (PM-CAES) has recently been suggested as a promising alternative to existing CAES plants. PM-CAES incurs repetitive two-phase fluid flow caused by the cyclic injection and withdrawal of air to/from the porous medium that is initially saturated with the formation water during the operation. Therefore, predicting the overall macro-scale performance of porous media for energy storage requires a better understanding of repetitive two-phase fluid flow in the pore network at the fundamental pore-scale level. To answer this need, we conducted an experimental study using the microfluidics technology; we constructed polydimethylsiloxane (PDMS)-based micromodels with two different geometries (Type I: circular solids and Type II: square solids) and three different structural heterogeneities (coefficient of variation: COV=0, 0.25 and 0.5). Then, we applied a total of ten injection-withdrawal cycles to each micromodel (i.e., ten cyclic drainage-imbibition processes) at different flow rate conditions (Q=0.01 and 0.1 ml/min). It was observed that the displacement patterns of the initially residing fluid (wetting fluid; oil in this study) and the injected fluid (non-wetting fluid; water in this study) were greatly influenced by the geometry and heterogeneity of the pore structure, and imposed flow rate. Results such as the effective sweep efficiency and residual saturation of the non-wetting fluid were analyzed at each drainage-imbibition cycle to aid in understanding the impact of repetitive fluid flow. The experimental observations imply that the flow rate and structural heterogeneity may influence the efficiency of PM-CAES more than the pore geometry does.

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Effects of coupled hydro-mechanical model considering two-phase fluid flow on potential for shallow landslides: a case study in Halmidang Mountain, Yongin, South Korea

10.5194/nhess-2019-271 ◽

2019 ◽

Author(s):

Sinhang Kang ◽

Byungmin Kim

Keyword(s):

Fluid Flow ◽

Slope Stability ◽

Single Phase ◽

Flow Model ◽

Coupled Model ◽

Shallow Landslides ◽

Single Phase Flow ◽

Two Phase ◽

Fully Coupled ◽

Phase Fluid

Abstract. More than 30 shallow landslides were caused by heavy rainfall that occurred on July 26 and 27, 2011, in Halmidang Mountain, Yongin-si, Gyeonggi Province, South Korea. To precisely analyze shallow landslides and to reflect the mechanism of fluid flow in void spaces of soils, we apply a fully coupled hydro-mechanical model considering two-phase fluid flow of water and air. The available GIS-based topographic data, geotechnical and hydrological properties, and historical rainfall data are used for infiltration and slope stability analyses. Changes in pore air and water pressures and saturations of air and water are obtained from the infiltration analysis, which were used to calculate the safety factor for slope stability assessment. By comparing the results from numerical models by applying a single-phase flow model and a fully coupled model, we investigate the effects of air flow and variations in hydraulic conductivity affected by stress–strain behavior of soil on slope stability. Our results suggest that air flow and hydro-mechanical coupling affects the rate of increase in pore water pressure, thus influencing the safety factor on slopes when ponding is more likely to occur during heavy rainfall. Finally, we conduct slope failure assessments using the fully coupled model, slightly more consistent with actual landslide events than the single-phase flow model.

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