Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session G31: Porous Media Flows V: CO2 Sequestration |
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Chair: Alfredo Soldati, University of Udine Room: 402 |
Monday, November 25, 2013 8:00AM - 8:13AM |
G31.00001: Experimental investigation of the infiltration of liquid CO2 into water-saturated, two-dimensional porous micro-models using micro-PIV F. Kazemifar, G. Blois, D.C. Kyritsis, K.T. Christensen A novel experimental apparatus has been developed to study the interaction of two immiscible fluids in a two-dimensional porous micro-model. The two fluids considered are liquid CO$_2$ and water. This flow process is relevant to many engineering applications such as sequestration of CO$_2$ in geological formations as well as enhanced oil recovery operations. Saline aquifers have very high potential for geological sequestration of CO$_2$ based on several factors, including high capacity, economics and minimum environmental impact. In such a process, CO$_2$ must displace the resident fluid of the porous structure; i.e. brine. The lower viscosity and density of CO$_2$ compared to brine results in complex mechanisms of brine displacement. While early studies focused on qualitative observations of fluid--fluid interactions, in this study, the microscopic particle image velocimetry technique is employed to simultaneously quantify the flow fields within each fluid phase. The interface dynamics, migration and trapping mechanisms are of particular interest. In such flows, viscosity and interfacial tension are the controlling parameters which, in the vicinity of the critical point, become very sensitive to changes in pressure and temperature. [Preview Abstract] |
Monday, November 25, 2013 8:13AM - 8:26AM |
G31.00002: Capillary pinning of immiscible gravity currents in porous media Benzhong Zhao, Christopher MacMinn, Herbert Huppert, Ruben Juanes Gravity currents in porous media have attracted interest recently in the context of geological carbon dioxide (CO$_2$) storage. Capillarity can be important in the spreading and migration of the buoyant CO$_2$ after injection because the typical pore size is very small, but the impact of capillarity on these flows is not well understood. Here, we study the impact of capillarity on the buoyant spreading of a finite gravity current of non-wetting fluid into a dense, wetting fluid in a vertically confined, horizontal aquifer. We show via simple, table-top experiments using glass bead packs that capillary pressure hysteresis pins a portion of the fluid-fluid interface. The horizontal extent of the pinned portion of the interface grows over time and this is responsible for ultimately stopping the spreading of the buoyant current after a finite distance. In addition, capillarity blunts the leading edge of the buoyant current. We demonstrate through micromodel experiments that the characteristic height of the nose of the current is controlled by the pore throat size distribution and the balance between capillarity and gravity. We develop a theoretical model that captures the evolution of immiscible gravity currents and predicts the maximum migration distance. [Preview Abstract] |
Monday, November 25, 2013 8:26AM - 8:39AM |
G31.00003: Onset of nonlinear convection in transient diffusive boundary layers: application to CO$_2$ sequestration Nils Tilton, Amir Riaz The linear stability of transient diffusive boundary layers in porous media has been studied extensively for applications to carbon dioxide sequestration. The onset of nonlinear convection, however, remains understudied because the transient base-state invalidates traditional weakly nonlinear stability methods. We study the onset of nonlinear convection using complementary asymptotic expansions and high-order direct numerical simulations (DNS). We first demonstrate by DNS that when a boundary layer is perturbed with a single Fourier mode, nonlinear mechanisms generate a zero-wavenumber response that becomes equal-order with the fundamental mode after the onset of nonlinear convection. This invalidates traditional weakly nonlinear methods that assume the zero-wavenumber response is small. Nevertheless, we demonstrate that the initial onset time of nonlinear convection can be accurately determined from a regular asymptotic expansion that is two orders-of-magnitude faster than DNS. Using the expansion, we find there is an optimal perturbation wavenumber and initial perturbation time that minimize the onset time of nonlinear convection. We obtain analytical relationships for these optimal parameters in terms of typical aquifer properties and initial perturbation magnitude. [Preview Abstract] |
Monday, November 25, 2013 8:39AM - 8:52AM |
G31.00004: Dissolution patterns from geochemical reactions during Rayleigh-Benard convection in porous media Xiaojing Fu, Luis Cueto-Felgueroso, Diogo Bolster, Ruben Juanes Convective mixing is an essential trapping mechanism during CO$_2$ sequestration in deep saline aquifers. Upon injection, buoyant CO$_2$ enters the geologic formation and mixes with the underlying brine, which leads to a local density increase that triggers density-driven flow; meanwhile, the presence of CO$_2$ disturbs the geochemical equilibrium of brine with respect to the formation, which can lead to dissolution or precipitation of carbonate minerals. Dissolution/precipitation reactions result in changes in porosity, which in turn induce changes in permeability that impact the flow dynamics. Motivated by the process of CO$_2$ convective mixing in deep saline aquifers, here we study the formation of rock-dissolution patterns that arise from geochemical reactions during Rayleigh-B\'enard convection in porous media. We perform high-resolution simulations to analyze the interplay between the density-driven hydrodynamic instability and the formation of high-porosity channels, explain the emergence of a characteristic length scale in the dissolution channels, and quantify the impact of the channelization process on the macroscopic convection rate. [Preview Abstract] |
Monday, November 25, 2013 8:52AM - 9:05AM |
G31.00005: Transient diffusive boundary layers in heterogeneous porous media Don Daniel, Amir Riaz The onset of convection of gravitationally unstable transient, diffusive boundary layers in saline aquifers has been extensively investigated due to its importance in carbon dioxide sequestration. However, due to theoretical complexities, the onset of convection in heterogeneous porous media with span-wise variation in permeability (varying crosswise to direction of gravity) has been relatively less explored. Unlike homogeneous porous media, we demonstrate that the onset of convection in such heterogeneous media is simultaneously triggered by a combination of several individual span-wise perturbation modes. Using a combination of linear stability analysis and numerical simulations, we obtain the dominant two dimensional global perturbation structures for different spatially varying permeability fields. We compare our results with previous literature for homogeneous porous media, and conclude whether the onset of convection in heterogeneous media is enhanced or delayed. [Preview Abstract] |
Monday, November 25, 2013 9:05AM - 9:18AM |
G31.00006: Stability of High Rayleigh-Number Equilibrium Solutions of the Darcy--Oberbeck--Boussinesq Equations Baole Wen, Lindsey Corson, Gregory Chini There has been significant renewed interest in dissolution-driven convection in porous layers owing to the potential impact of this process on carbon dioxide storage in terrestrial aquifers. In this talk, we present some numerically-exact equilibrium solutions to the porous medium convection problem in small laterally-periodic domains at high Rayleigh number $Ra$. The ``uni-cellular'' equilibrium solutions first found by Corson and Chini (2011) by solving the steady Darcy--Oberbeck--Boussinesq equations are recovered and, in the interior (i.e. away from upper and lower boundary layers), are shown to have the same horizontal-mean structure as the ``heat-exchanger'' solutions identified by Hewitt et al. (2012). Secondary stability analysis of the steady solutions is performed, and implications for high-Ra porous medium convection are discussed. [Preview Abstract] |
Monday, November 25, 2013 9:18AM - 9:31AM |
G31.00007: Dissolution driven convection for carbon dioxide sequestration: the stability problem Shreyas Mandre, Xinjun Guo, Anja Slim The dissolution-driven convection in porous media is potentially a rate limiting process for sequestering carbon dioxide in underground aquifers. Super critical carbon dioxide introduced in the aquifer is lighter than the water that fills the surrounding porous rock, and hence quickly rises to the top. However, the solution of carbon dioxide in water is heavier than water. Hence, as the layer of carbon dioxide dissolves in the water, convection may ensue. The threshold criteria for convection is obscured by the continually changing background density profile as the carbon dioxide diffuses through the pores. Commonly used techniques such as frozen coefficient analysis or non-modal theories using transient amplifications yield substantially different results for the threshold, which has been the cause of a debate in the scientific community. We present a general theory for the linear stability of non-autonomous systems and apply it to dissolution driven convection. The theory unifies the classical modal stability theory using eigenvalues, the non-modal approaches using optimal growth of energy and the frozen coefficient analysis. We settle the debate, and demonstrate the existence of a threshold time for convection to commence. [Preview Abstract] |
Monday, November 25, 2013 9:31AM - 9:44AM |
G31.00008: Hazards from a massive release of CO2 such as the 1986 Lake Nyos event Diana Sher, Andrew Woods We report a series of new experiments exploring the dynamics of gravity currents in which a volume of dense fluid is released from a lock gate and spreads along a flume into the ambient fluid. Using new experimental data, we develop a model for the evolution of the current with time, and in particular, the evolution of the flow passing through a given point with time. We apply this to interpret the hazards associated with a large release of dense gas, such as occurred in 1986 at Lake Nyos, Cameroon, when about 0.1 cubic km of CO2 was released from the lake and travelled down a valley as a dense gravity current. [Preview Abstract] |
Monday, November 25, 2013 9:44AM - 9:57AM |
G31.00009: Impact of wettability on two-phase displacement patterns in granular media Ruben Juanes, Mathias Trojer, Michael Szulczewski, Ran Holtzman Two phase flow in porous media controls many natural processes like geological CO2 sequestration, enhanced oil recovery, water infiltration in soil, and methane venting from organic-rich sediments. While the wetting properties of rocks can vary drastically, the effect of wettability on fluid displacement in porous media remains poorly understood. Here, we study experimentally how wettability affects the fluid-fluid displacement pattern in rigid granular media within the capillary and viscous fingering regime. We inject a less viscous fluid into a thin bed of glass beads, initially fully saturated with a more viscous one. By keeping all control parameters constant and changing the contact angle of the substrate systematically, we visually explore and quantify the impact of the wetting properties on the invasion morphology. For fixed capillary number, we show that the invasion pattern becomes more stable as the contact angle increases (i.e., as we transition from drainage to imbibition) both in the capillary-fingering and in the viscous-fingering regime. We quantify the dependence of the lengthscale of the instability on contact angle, and propose a mechanistic pore-scale model that explains the macroscopic observations. [Preview Abstract] |
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