Transport in Porous Media最新文献

To meet the extensive demand for lithium (Li) for rechargeable batteries, it is crucial to enhance Li production by diversifying its resources. Recent studies have found that produced water from shale reservoirs contains various organic and inorganic components, including a significant amount of Li. In this study, findings from hydrothermal reaction experiments were analyzed to fully understand the release of Li from organic-rich shale rock. Subsequently, numerical algorithms were developed for both pore-scale and continuum-scale models to simulate the long-term behavior of Li in shale brines. The experimental conditions considered four different hydrothermal solutions, including the solutions of KCl, MgCl₂, CaCl₂, and NaCl with various concentrations under the temperature of 130 °C, 165 °C, and 200 °C. The release of Li from shale rock into fluid was regarded as a chemical interaction of cation exchange between rock and fluid. The reactive transport pore-scale and upscaled continuum-scale models were developed by coupling the chemical reaction model of Li interaction between rock and fluid. The model was first implemented to investigate the release and transport of Li in the pore scale. Continuum-scale properties, such as effective diffusivity coefficients and Li release rate, were obtained as the field-averaged pore-scale modeling results. These properties were used as the input data for the upscaled continuum-scale simulation. The findings of this study are expected to provide new insight into the production of Li from shale brines by elucidating the release, fate, and transport of Li in subsurface formations.

Colloid particle size plays an important role in contaminant adsorption and clogging in the hyporheic zone, but it remains unclear how the particle size changes during the transport of colloids. This study investigated the variation of the particle size of colloids in the overlying water and the effects of settlement and hyporheic exchange via laboratory experiments and numerical simulations with two main factors settlement and hyporheic exchange being considered. The results show that the particle size distribution varies when colloids transport in hyporheic zone, and both settlement and hyporheic exchange are involved in the exchange of colloids between stream and streambed. Large-sized particles are mainly controlled by settlement and advection and thus their concentration in the overlying water decreases more quickly; but small-sized particles are mainly controlled by hyporheic exchange and thus their concentration decreases more slowly, and some particles can be resuspended. The increase of retention coefficient and settling velocity will accelerate the transfer of colloids into the streambed. This study may provide important insights into the variation of the particle size of colloids in the overlying water and the effects of settlement and hyporheic exchange.

The pore-scale numerical modeling of CO₂ injection into natural rock saturated with oil–water mixture was performed using the density functional hydrodynamics approach. The detailed 3D digital model of the sandstone core sample contained over 7 billion cells, which allowed us to perform analysis of oil displacement efficiency at different scales. Utilization of large-size detailed numerical models make it possible to characterize, both qualitatively and quantitatively, the processes at pore scale to the level of detail not achievable on smaller models. The obtained results indicate large-scale effects even on relatively heterogeneous core indicating possible need for multiscale hierarchical models even in heterogeneous cases. This fact imposes the demand for scalability performance on both the software and hardware used in such simulations, as well as the need for adequate modeling upscaling methods.

Natural fractures in subsurface reservoirs are frequently partially cemented with mineral precipitates, and it is unclear if fracture permeability models developed for rough barren fractures are applicable for fractures where roughness originates from cement linings. Here, we use a digital rock physics workflow to quantify the error in fracture permeability predicted by these models for five digitally synthesized rough fractures and four fractures imaged using three-dimensional X-ray computed microtomography. Samples include a rough, artificially-induced barren fracture in sandstone, a cement-lined natural fracture in limestone sampled from outcrop, and two cement-bridged natural fractures in tight-gas sandstones sampled from reservoir core. The images are then processed, segmented, characterized to determine statistical moments of the aperture distribution, and used in lattice Boltzmann model flow simulations. We address complications in measuring aperture distributions from images when the fracture pore space morphology deviates from the typical theoretical description of rough fractures and evaluate three different methods of measuring local aperture. The alternative cubic law using the nominal mean aperture is found to overestimate fracture permeability by upwards of one to two orders of magnitude, while the fracture permeability models using statistical moments of the aperture distribution are far more accurate for both rough barren and partially cemented fractures. We also define an empirical description of the upper and lower bounds of fracture permeability estimates as a function of relative roughness that is applicable to both rough barren and partially cemented fractures.

Much of the continental margins in the world oceans provide the necessary thermodynamic conditions to store CO(_2) as ice-like hydrates (CO(_2cdot)6 H(_2)O). While resistant to buoyant migration and leakage, the fundamental growth mechanisms that control the injection, capacity, and security of CO(_2) hydrates stored in the seafloor remain unresolved. Extensive field and laboratory testing give rise to conflicting views on the kinetics and growth configurations of hydrates, where mechanistic models reconciling the formation of hydrates observed in nature remain missing. This work elucidates a fundamental pore-scale reactive transport mechanism that underpins the rate and morphology of hydrate formation. We reveal a previously unrecognized mode of hydrate formation in porous seafloor sediments, hydrate film growth via reaction-imbibition, where superhydrophilic hydrate crystallites ((theta sim 0^circ)) formed at water–CO(_2) interfaces create a secondary microporous medium ((sim) 10 to 100 nm pores) within lithologic sediment pores ((sim) 10 to 100 (mu)m pores) to promote further hydrate growth. Unlike past diffusion-controlled models, we show that spontaneous water imbibition into the hydrate micropores establishes rapidly new water–CO(_2) interfaces (i.e., hydrate formation surfaces) via capillary-driven convection and is the dominant mechanism for supplying water to the hydrate formation interface.

The capillary pressure defines pressure difference between non-wetting and wetting fluids. The capillary pressure is part of the flow governing equations, and its definition can have a profound impact on the nature of fluids displacement in a multiphase flow environment. Conventionally, capillary pressure–saturation relationships are determined under equilibrium conditions which signify that all the fluid–fluid interfaces that exist at the pore scale maintain a static configuration at a certain instant in time. However, there exist experimental and numerical evidences that state that the dynamic nature of fluid flows indeed plays a prominent role in defining the trends of the capillary pressure–saturation relationships. In this paper, we develop a first of a kind semi-analytical model to predict the capillary pressure–saturation curves during drainage displacement by integrating the dynamics of fluid flow based on fundamental laws of fluid mechanics. The proposed semi-analytical model can potentially be incorporated into existing multiphase flow simulators to rapidly compute the capillary pressure at various saturations of the flow medium under dynamic flow conditions. The presented semi-analytical model has been validated against experimental and numerical data sets available in the literature at various flow conditions and considering different sets of fluid properties. We noticed a satisfactory match of the results predicted by the proposed semi-analytical model against the literature data. After performing a holistic sensitivity analysis, we notice that the properties of the porous medium, and the fluid–solid interactions play a significant role in defining the trends of the capillary pressure–saturation curves.