Wettability impact on supercritical CO 2 capillary trapping: Pore‐scale visualization and quantification

Geophysical Research Letters

et al. 2018

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As externally imposed flow rate increases during imbibition, viscous force increasingly dominates displacement over capillarity and imbibition shifts from capillary to capillary‐viscous regimes. Previous studies focused on capillary regime, lacking a fundamental understanding of regime transition. Here we study the imbibition transition via flow rate‐controlled experiments in a rough fracture. By analyzing energy balance in multiphase flow system, we find a fundamental link between regime transition and energy conversion. In capillary regime, surface energy is partially transformed into external work and an amount of 51−58% is dissipated via local rapid, irreversible events; while in capillary‐viscous regime, surface energy together with external work is transformed into kinetic and dissipated energies. This transition, corresponding to critical capillary number, is evidenced by quantitative analysis of invasion morphologies. Our work bridges the gap between energy conversion/dissipation and multiphase flow and has important implications for identifying imbibition regimes in enhanced oil recovery and geological CO2 sequestration.

Section: Resultsmentioning

confidence: 99%

Energy Conversion Reveals Regime Transition of Imbibition in a Rough Fracture

Geophysical Research Letters

et al. 2018

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“…Since the viscosity of brine is higher than that of supercritical (sc)CO 2 , the displacement front tends to become compact and stable as flow rate increases. However, change in wettability of rock surfaces resulting from the sorption of natural organic matter and hydrocarbons, or the long‐term exposure to CO 2 (El‐Maghraby & Blunt, ; Iglauer et al, ; Kim et al, ) significantly affects the stability of displacement fronts and directly impacts the scCO 2 capillary trapping (Chaudhary et al, ; Hu et al, ). Therefore, quantifying the competing effects of wettability and flow rate on the displacement front instability during the postinjection stage becomes a critical issue to be addressed.…”

Section: Introductionmentioning

confidence: 99%

Wettability and Flow Rate Impacts on Immiscible Displacement: A Theoretical Model

Wan

Geophysical Research Letters

et al. 2018

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118

When a more viscous fluid displaces a less viscous one in porous media, viscous pressure drop stabilizes the displacement front against capillary pressure fluctuation. For this favorable viscous ratio conditions, previous studies focused on the front instability under slow flow conditions but did not address competing effects of wettability and flow rate. Here we study how this competition controls displacement patterns. We propose a theoretical model that describes the crossover from fingering to stable flow as a function of invading fluid contact angle θ and capillary number Ca. The phase diagram predicted by the model shows that decreasing θ stabilizes the displacement for θ≥45° and the critical contact angle θc increases with Ca. The boundary between corner flow and cooperative filling for θ < 45° is also described. This work extends the classic phase diagram and has potential applications in predicting CO2 capillary trapping and manipulating wettability to enhance gas/oil displacement efficiency.

“…Immiscible displacement patterns have been shown to be influenced by the wetting conditions (e.g., Dou et al, ; Holtzman & Segre, ; Hu et al, , ; Jung et al, ; Trojer et al, ). Here, we have also simulated the displacement patterns under weak drainage condition (contact angle 60°), as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

Modeling Immiscible Two‐Phase Flow in Rough Fractures From Capillary to Viscous Fingering

Water Resources Research

Méheust

Neuweiler

et al. 2019

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We develop an efficient computational model for simulating fluid invasion patterns emerging in variable aperture fractures. This two‐dimensional model takes into account the effect of capillary force on the fluid‐fluid interfaces and viscous pressure drop in both fluid phases. The pressure distribution is solved at each time step based on mass balance and local cubic law, considering an imposed pressure jump condition at the fluid‐fluid interface. This pressure jump corresponds to the Laplace pressure which includes both terms related to the out‐of‐plane (aperture‐spanning) curvature and to the in‐plane curvature. Simulating a configuration that emulates viscous fingering in two‐dimensional random porous media confirms that the model accounts properly for the role of viscous forces. Furthermore, direct comparison with previously obtained experimental results shows that the model reproduces the observed drainage patterns in a rough fracture reasonably well. The evolutions of tip location, the inlet pressures, and the invading phase fractal dimensions are analyzed to characterize the transition from capillary fingering to viscous fingering regimes. A radial injection scenario of immiscible invasion is also studied with varying modified capillary number and viscosity ratio, showing displacement patterns ranging from capillary fingering to viscous fingering to stable displacement. Such simulations using two contact angles show that the invading phase becomes more compact when the wetting condition changes from strong to weak drainage, as already observed in 2‐D porous media. The model can be used to bridge the gap in spatial scales of two‐phase flow between pore‐scale modeling approaches and the continuum Darcy‐scale models.