Gravity‐Induced Bubble Ripening in Porous Media and Its Impact on Capillary Trapping Stability

Xu, Ke; Mehmani, Yashar; Shang, Luoran; Xiong, Qingrong

doi:10.1029/2019gl085175

Cited by 26 publications

(21 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Garing et al (25) experimentally measured the equilibrium capillary pressure of trapped air bubbles inside sandstone and bead-pack samples. They found that, unlike bubbles within a bulk fluid, the P c of trapped bubbles shows no clear dependence on V and seems to fall within a bounded interval, except for vanishingly small V. Xu et al (40) proposed an empirical correlation for the P c trapped bubbles based on microfluidic observations. In this correlation, as V increases, P c decreases until a minimum is reached and then increases linearly.…”

mentioning

confidence: 99%

Capillary equilibrium of bubbles in porous media

Wang

Mehmani

2021

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

In geologic, biologic, and engineering porous media, bubbles (or droplets, ganglia) emerge in the aftermath of flow, phase change, or chemical reactions, where capillary equilibrium of bubbles significantly impacts the hydraulic, transport, and reactive processes. There has previously been great progress in general understanding of capillarity in porous media, but specific investigation into bubbles is lacking. Here, we propose a conceptual model of a bubble’s capillary equilibrium associated with free energy inside a porous medium. We quantify the multistability and hysteretic behaviors of a bubble induced by multiple state variables and study the impacts of pore geometry and wettability. Surprisingly, our model provides a compact explanation of counterintuitive observations that bubble populations within porous media can be thermodynamically stable despite their large specific area by analyzing the relationship between free energy and bubble volume. This work provides a perspective for understanding dispersed fluids in porous media that is relevant to CO2 sequestration, petroleum recovery, and fuel cells, among other applications.

show abstract

mentioning

confidence: 99%

Capillary equilibrium of bubbles in porous media

Wang

Mehmani

2021

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…questions about basis for the extrapolation to "field rates" for estimating critical gas saturation. It is possible that at field scale large column height can lead gravity-induced ripening [51] creating possible connected paths and associated mobility. The growth kinetics, however, is diffusion limited which is expected to occur on a time scale of years at relevant length scales [51].…”

Section: Discussionmentioning

confidence: 99%

“…Even though diffusion is only impacted in the percent range by the geometric constraint of the pore space, the increase in curvature and the associated (capillary) pressure for growth past a pore throat causes a de-facto anti-ripening effect with pore throats acting as barriers for growth [49] which can only be overcome by a significant driving forces, e.g. significant gravity potential over large column height [51]. Ultimately, both phenomena of ripening and anti-ripening are the result of the same underlying physical process of coarsening in porous media.…”

Section: Pore Scale Fluid Configuration In the 2-component Systemmentioning

confidence: 99%

Capillarity and phase-mobility of a hydrocarbon gas–liquid system

Gao

Georgiadis

Brussee

et al. 2021

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

View full text Add to dashboard Cite

When oil fields fall during their lifetime below the bubble point gas comes out of solution. The key questions are at which saturation the gas becomes mobile (“critical gas saturation”) and what the gas mobility is, because mobile gas reduces the production of oil significantly. The traditional view is that the gas phase becomes mobile once gas bubbles grow or expand to a size where they connect and form a percolating path. For typical 3D porous media the saturation corresponding to this percolation limit is on the order of 20%. However, significant literature report on gas mobility below lower limits of percolation thresholds i.e. below 0.1%. A direct experimental insight for that is lacking because laboratory measurements are notoriously difficult since the formation of gas bubbles below the bubble point includes thermodynamic and kinetic aspects, and the pressure decline rates achievable in laboratory experiments are orders of magnitude higher than the decline rates in the field. Here we study the nucleation and transport of gas coming out of solution in-situ in 3D rock using X-ray computed micro tomography which allows direct visualization of the nucleation kinetics and connectivity of gas. We use either propane or a propane–decane mixture as model system and conduct pressure depletion in absence of flow finding that – consistent with the literature – observation of the bubble point in the porous medium is decreased and becomes pressure decline rate dependent because of the bubble nucleation kinetics. That occurs in single-component systems and in hydrocarbon mixtures. Pressure depletion in absence of flow results in critical gas saturations between 20 and 30% which is consistent with typical percolation thresholds in 3D porous structures. That does not explain experimentally observed critical gas saturations significantly below 20%. Also, the respective pore level fluid occupancy where pores are filled with either gas or liquid phase but not partially with both as in normal 2-phase immiscible systems rather diminishes connectivity of gas and liquid phases. This observation indicates that likely other mechanisms play a role in establishing gas mobility at saturations significantly below 20%. Experiments under flow conditions, where gas is injected near the bubble point suggest that diffusion may significantly contribute to the transport of gas and may even be the dominant transport mechanism at field relevant flow rates. The consequence of diffusive transport are compositional gradients where locally the composition is such gas nucleation may occur. That would lead to a disconnected but mobile gas distribution ahead of the convective front. Furthermore, diffusive exchange leads to ripening and anti-ripening effects which influences the distribution for which we see evidence in pressure depletion experiments but not so much at low rate gas injection. Respective relative permeability computed from the imaged fluid distributions using a lattice Boltzmann approach show distinctly different behavior between pressure depletion and flowing conditions. These findings suggest that capillarity in a gas–liquid hydrocarbon mixture is far more complex than in a 2-phase immiscible system. Capillarity is coupled to phase behavior thermodynamics and kinetics on a fast time scale and diffusion-dominated mechanisms such as ripening and anti-ripening effects at a slow time scale. While the consequences for the current experimental and field modelling approaches are not yet fully clear, this shows that more research is needed to fully understand these effects and their implications.

show abstract

“…The selected simulation parameters are listed in Table S1 in Supporting Information . The liquid and gas phases are brine and scCO 2 , and some parameters are obtained from the literature(Busch & Amann‐Hildenbrand, 2013; Liu et al., 2012; Xu et al., 2019).…”

Section: Numerical Analysismentioning

confidence: 99%

“…A study using an isothermal gravity/chemical equilibrium model found that the composition of oil and gas mixtures stored in deep strata changed significantly with the depth, and gravity affected the chemical potential of the phase, resulting in the redistribution of the gas‐liquid composition in the vertical direction (Wheaton, 1991; Whitson & Belery, 1994). A gravity‐induced ripening bubble model was proposed for the first time to investigate the temporal variation of the bubbles in different pore structures during ripening in the mass transfer process (Xu et al., 2019). The theoretical mass transfer time obtained by this theoretical model is relatively long, and gravity can affect the process by altering the magnitude and direction of chemical potential gradients.…”

Section: Introductionmentioning

confidence: 99%

The Influence of the Hypergravity Field During Bubble Ripening in Porous Media

Chen

et al. 2022

Geophysical Research Letters

View full text Add to dashboard Cite

Carbon dioxide (CO 2 ) geological storage is an appropriate long-term option to reduce carbon emissions. CO 2 in the supercritical (sc) state is injected into abandoned oil and gas deposit areas or deep brine layers at depths below 1 km (Bachu, 2016;Dai et al., 2014). The deep brine layer is considered a potential carbon storage area due to its permeable sedimentary rock structure saturated with brine and the lower permeability of the caprock (Gilfillan et al., 2009;Mbia et al., 2014). Studies have shown that CO 2 injected into deep geologic formations is sequestered by four processes: structural trapping, residual trapping, dissolution trapping, and mineral trapping. The safety of these four processes is continuously improving (Ampomah et al., 2016;S. Krevor et al., 2015). However, the bubbles in the stable residual trapping state undergo secondary migration due to dissolution and diffusion to the continuous gas layer in the structure trapping state, that is, the Ostwald ripening process occurs, which adversely affects the safety of the carbon sequestration process.As a major mechanism of the long-term safety of a carbon storage project, residual trapping is traditionally considered an efficient and safe method (Benson & Cole, 2008). The resistance generated by the pore structure causes bubbles with a radius of the same order of magnitude or higher as the pore size to be trapped in the porous medium in the form of ganglia, which is referred to as the residual trapping state (Andrew et al., 2015; S. C. M. Krevor et al., 2011). A small number of adjacent ganglia can reach the local capillary equilibrium rapidly, the gradients in the fluid pressure and buoyancy occur predominantly at spatial scales of meters and greater (Jackson & Krevor, 2020).Ostwald ripening describes the process of mass transfer from small bubbles to large bubbles through dissolution in the liquid phase driven by the capillary pressure or the chemical potential gradient in a gas-liquid two-phase system (Voorhees, 1985(Voorhees, , 1992. Ripening, which reduces the potential energy of the entire system by merging bubbles, is a thermodynamically stable process in the long term. Some bubbles continue to expand until they are squeezed and deformed by the pore structure. The capillary force of the bubbles is correlated with the geometric characteristics of the pores (Garing et al., 2017). Xu et al. ( 2017) developed a kinetics model for a group of bubbles to describe the ripening and mass transfer of bubbles in porous media and designed a 2.5D microfluidic chip for verification. Li et al. (2020) put forward a mathematical model and observed that the Ostwald ripening process came to equilibrium in several years on the millimeter to centimeter scale in a geological system.

show abstract

Gravity‐Induced Bubble Ripening in Porous Media and Its Impact on Capillary Trapping Stability

Cited by 26 publications

References 35 publications

Capillary equilibrium of bubbles in porous media

Capillary equilibrium of bubbles in porous media

Capillarity and phase-mobility of a hydrocarbon gas–liquid system

The Influence of the Hypergravity Field During Bubble Ripening in Porous Media

Contact Info

Product

Resources

About