Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session M40: Porous Media Flows: CO2 Sequestration and Convection |
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Chair: Farzan Kazemifar, University of Notre Dame Room: Portland Ballroom 253-258-254-257 |
Tuesday, November 22, 2016 8:00AM - 8:13AM |
M40.00001: Experimental quantification of pore-scale flow of water and liquid CO2 in 2D heterogeneous porous micromodels at reservoir conditions Yaofa Li, Farzan Kazemifar, Gianluca Blois, Kenneth Christensen Pore-scale flow interactions between water and supercritical CO$_{2}$ is relevant to large-scale geologic sequestration of CO$_{2}$. Recent studies have provided evidence of strong instabilities at the meniscus resulting in burst events and onset of inertial effects. This supports the notion that pore-scale physics cannot be captured by Darcian models and unsteady events play a defining role in CO$_{2}$ transport/trapping processes and such burst events may generate pressure fluctuations that can be linked to micro-seismic events in the pore structure. To this end, the pore-scale flow of water and liquid/supercritical CO$_{2}$ is investigated under reservoir-relevant conditions in 2D heterogeneous porous micro-models that reflect the complexity of a real sandstone. Fluorescent microscopy and micro-PIV are complemented by a fast differential pressure transmitter, allowing for simultaneous quantification of the flow field within and the instantaneous pressure drop across the micromodels. A number of CO$_{2}$ invasion patterns and corresponding pressure drop variations are observed over a range of wettability conditions, yielding a more comprehensive picture of the CO$_{2}$ drainage processes. [Preview Abstract] |
Tuesday, November 22, 2016 8:13AM - 8:26AM |
M40.00002: A new approach to the stability analysis of transient natural convection in porous media Nils Tilton Onset of natural convection due to transient diffusion in porous media has attracted considerable attention for its applications to CO$_2$ sequestration. Stability analyses typically investigate onset of convection using an initial value problem approach in which a perturbation is introduced to the concentration field at an initial time $t=t_p$. This leads to debate concerning physically appropriate perturbations, the critical time $t_c$ for linear instability, and to the counter-intuitive notion of an optimal initial time $t_p$ that maximizes perturbation growth. We propose a new approach in which transient diffusion is continuously perturbed by small variations in the porosity. With this approach, instability occurs immediately ($t_c=0$) without violating any physical constraints, such that the concepts of initial time $t_p$ and critical time $t_c$ have less relevance. We argue that the onset time for nonlinear convection is a more physically relevant parameter, and show that it can be predicted using a simple asymptotic expansion. Using the expansion, we consider porosity perturbations that vary sinusoidally in the horizontal and vertical directions, and show there are optimal combinations of wavelengths that minimize the onset time of nonlinear convection. [Preview Abstract] |
Tuesday, November 22, 2016 8:26AM - 8:39AM |
M40.00003: Modeling the convective stability of $CO_2$ sequestration by a discontinuous and unstably stratified density profile Taber Wanstall, Layachi Hadji The convective stability associated with carbon sequestration is modeled by adopting an unstably stratified basic profile having a step function density with top heavy carbon saturated layer overlying a lighter carbon free layer. The model takes into account the anisotropy in both permeability and carbon dioxide diffusion, and chemical reactions between the $CO_2$ rich brine and host mineralogy. We carry out a linear stability analysis to derive the instability threshold parameters for a variety of $CO_2$ boundary conditions. We solve for the minimum thickness of the carbon-rich layer at which convection sets in and quantify how its value is influenced by diffusion, anisotropy, permeability, reaction and type of boundary conditions. The discontinuity leads to convective concentration contours that have the shape of an asymmetric lens which we quantify by deriving and making use of the $CO_2$ flux expressions at the interface. The linear problem is extended to the nonlinear regime, the analysis of which leads to the determination of a uniformly valid super critical steady solution. [Preview Abstract] |
Tuesday, November 22, 2016 8:39AM - 8:52AM |
M40.00004: Density driven convection with dissolution in porous media: experiment, simulation and linear stability analysis Xuhui Meng, Xiaofan Yang, Zhaoli Guo Geological storage of the CO2 in subsurface saline aquifers is a promising way to reduce CO2 emissions. During this process, CO2 first dissolves into pure brine. Then the acidic and denser mixture falls down under the gravity and reacts with the rock. In the present work, a microfluidic experiment is conducted to investigate the density-driven convection with dissolution in porous media. Moreover, the linear stability analysis and numerical simulations are further performed to investigate the interfacial instability. The results demonstrate that front instability can be triggered by the density contrast between the two miscible fluids, leading to the Rayleigh-Taylor instability. While this type of instability can be suppressed by the surface reaction between the fluid and solid phases, which prevents the transport of the denser fluid to the deeper region at the beginning. Over the long term, it is found that the interfacial instability can be influenced by the evolution of the porosity due to the dissolution, which will drive the transport of denser fluid further down. Our investigation shows that the transport of the reactive fluid in porous media depends on the competition among the density contrast, the chemical reaction rate and the evolution of the porosity/permeability. [Preview Abstract] |
Tuesday, November 22, 2016 8:52AM - 9:05AM |
M40.00005: Dynamics and mass transport of solutal convection in a closed porous media system Baole Wen, Daria Akhbari, Marc Hesse Most of the recent studies of CO$_2$ sequestration are performed in open systems where the constant partial pressure of CO$_2$ in the vapor phase results in a time-invariant saturated concentration of CO$_2$ in the brine ($C_s$). However, in some closed natural CO$_2$ reservoirs, e.g., Bravo Dome in New Mexico, the continuous dissolution of CO$_2$ leads to a pressure drop in the gas that is accompanied by a reduction of $C_s$ and thereby affects the dynamics and mass transport of convection in the brine. In this talk, I discuss the characteristics of convective CO$_2$ dissolution in a closed system. The gas is assumed to be ideal and its solubility given by Henry's law. An analytical solution shows that the diffusive base state is no longer self-similar and that diffusive mass transfer declines rapidly. Scaling analysis reveals that the volume ratio of brine and gas $\eta$ determines the behavior of the system. DNS show that no constant flux regime exists for $\eta > 0$; nevertheless, the quantity $F/C_s^2$ remains constant, where $F$ is the dissolution flux. The onset time is only affected by $\eta$ when the Rayleigh number $Ra$ is small. In this case, the drop in $C_s$ during the initial diffusive regime significantly reduces the effective $Ra$ and therefore delays the onset. [Preview Abstract] |
Tuesday, November 22, 2016 9:05AM - 9:18AM |
M40.00006: Convective dissolution in anisotropic porous media Marco De Paoli, Francesco Zonta, Alfredo Soldati Solute convection in porous media at high Rayleigh-Darcy numbers has important fundamental features and may also bear implications for geological $CO_2$ sequestration processes. With the aid of direct numerical simulations, we examine the role of anisotropic permeability $\gamma$ (the vertical-to-horizontal permeability ratio) on the distribution of solutal concentration in fluid saturated porous medium. Interestingly, we find that the finite-time (short-term) amount of solute that can be dissolved in anisotropic sedimentary rocks ($\gamma<1$, i.e. vertical permeability smaller than horizontal permeability) is much larger than in isotropic rocks. We link this seemingly counterintuitive effect with the occurring modifications to the flow topology in the anisotropic conditions. [Preview Abstract] |
Tuesday, November 22, 2016 9:18AM - 9:31AM |
M40.00007: Non-Boussinesq Dissolution-Driven Convection in Two- and Three-Dimensional Porous Media at Partially-Saturated Condition Mohammad Amin Amooie, Mohammad Reza Soltanian, Joachim Moortgat Sequestrated carbon dioxide (CO2) into saline aquifers, increases brine density through dissolution, and leads to gravitational instability and convective mixing. Traditionally, only the underlying brine-saturated subdomain is studied to avoid two-phase systems while replacing the gas cap atop with a constant, fully-saturated boundary condition. This violates the interface movement, neglects the capillary transition zone across original phases, and imposes constant density at top boundary insensitive to convective downwelling flow. Moreover, dissolution causes volume swelling, reflected as pressure build-up in absence of interface (movement), which further increases the fluid density --not captured under Boussinesq approximation. Here we accurately model the nonlinear phase behavior of brine-CO2 mixture, altered by dissolution and compressibility. We inject CO2 at a sufficiently low injection rate to maintain the single, partially-saturated phase, with no constraint on pressure and composition, so that density at top is free to change against the rate at which dissolved CO2 migrates downwards. We discover new flow regimes and present quantitative scaling relations for their temporal evolution in both two- and three-dimensional porous media. [Preview Abstract] |
Tuesday, November 22, 2016 9:31AM - 9:44AM |
M40.00008: Transient buoyant convection from a discrete source in porous media Ali Moradi, Morris Flynn The study of porous media filling box flows informs (i) the dissolution of non-aqueous phase liquids or sequestered CO$_2$ into potable groundwater, (ii) leakage of contaminants from waste piles, and (iii) enhanced oil recovery technologies. Here we examine the flow of a negatively buoyant, laminar plume in a box filled with a porous medium, which is connected to an infinite external ambient via upper and lower fissures. As $t \to \infty$, the box contains two uniform layers of different densities. However, the approach towards steady state is characterized by a lower (contaminated) layer that is continuously stratified and is governed by the ratios of the virtual origin correction and lower fissure depth to the box height, and the ratio, $\mu$, of the draining timescale to the filling timescale. Whereas the presence of a continuous stratification in the contaminated layer for finite time poses analytical challenges, we show that it is possible to derive bounds on the range of possible solutions. A separate component of our study considers time-variable forcing where the plume source strength is either abruptly altered or turned on and off with fixed half-period. Throughout, comparisons are drawn against filling boxes driven by turbulent free plumes. [Preview Abstract] |
Tuesday, November 22, 2016 9:44AM - 9:57AM |
M40.00009: Thermo-miscible fluid displacement in a porous media flow Thomas Ward, Tejaswi Soori The an-isoviscous displacement of a generalized Newtonian liquid in an impulsively heated axisymmetric pipe geometry is studied at low to moderate Reynolds numbers using computational analysis. The temperature dependent viscosity is modeled using an empirical correlation that has been shown to fit experimental data for a range of temperature values. The governing Cauchy momentum equations for the generalized Newtonian fluid are solved in primitive variables using a 4th order Runge-Kutta method. For viscous liquids with a high Prandtl number radial and axial variations in temperature are significant leading to modification of the steady state pressure loss when compared to isoviscous displacements. We characterize the steady state pressure loss and average Nusselt number using the Reynolds $0.1 < Re < 10$, viscous Atwood $0 < At < 0.8$, and Peclet $100 < Pe < 10,000$ numbers. [Preview Abstract] |
Tuesday, November 22, 2016 9:57AM - 10:10AM |
M40.00010: Saffman-Taylor instability in a rough fracture: beyond Darcy’s law Amir Pahlavan, Luis Cueto-Felgueroso, Gareth McKinley, Ruben Juanes The interplay between wetting and disorder, as well as the inherent complexity of porous media renders the description of immiscible flows a daunting task. To shed light on this problem, we conduct experiments on rough radial Hele-Shaw cells. We fill the cell with a viscous glycerol, and then inject a less viscous silicone oil at the center of the cell. The surfaces are treated to alter their wettability, allowing us to study both drainage and imbibition regimes. Viscous forces tend to destabilize the interfaces, whereas capillary forces play a stabilizing role; however, the disorder in the medium complicates this balance: 1) it leads to heterogeneities in the permeability field and capillary pressure distribution, and 2) it changes the effective wettability of the medium and leads to contact line pinning and hysteresis. We observe that at high capillary numbers, the disorder only weakly modulates the patterns, whereas at low capillary numbers, it affects the flow pattern significantly; the disorder leads to preferential flow paths in the drainage regime, and pinning and intermittent avalanche-like behavior in the imbibition regime. Inspired by these observations, we construct a phase-field model that takes the chemical potential gradients into account, going beyond Darcy's law. [Preview Abstract] |
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