1- Computational Modeling of Multiphase Flow in Porous Media

I study modeling and characterization of multiphase flow in porous media with application in the areas of energy and environment. I have developed a pore-scale fluid flow simulator using the lattice Boltzmann method. Our simulator is a powerful tool, which can handle multiphase flow simulations in geometric features obtained from the X-ray tomography image data of realistic rock formations. To improve the computational efficiency of simulations, the model has been applied to a parallel scheme written in C++ using the Message Passing Interface (MPI). I use high performance computing facilities of the Texas Advanced Computing Center (TACC) to perform the intensive simulations.

To learn more, please see Bakhshian et al.,  Sci. Rep., 2019.


1.1. Wettability Effects on Dynamics of Two-Phase Flow in Heterogeneous Porous Medi

Wettability plays an important role in the dynamics of the immiscible displacement at pore-scale.  To provide an improved understanding of pore-scale mechanisms controlling two-phase flow under a wide range of wettability conditions, quantifying the effect of wettability on the invasion patterns is performed through calculating the recovery efficiency of the defending fluid and curvature distribution of the interface. Our findings show how the geometrical and topological properties of porous media influence the optimal wetting conditions for maximizing the recovery of the defending fluid.

The corresponding publication is coming out soon ….



2- CO2 Sequestration in the Subsurface

Multiphase flow behavior is a key parameter in terms of assessing the economics and technical feasibility of carbon capture and storage (CCS) projects. Using the developed pore-scale fluid flow simulator, I study multiphase flow displacement in realistic three-dimensional (3D) rock samples for modeling of CO2 geo-sequestration in saline acquirers.

To learn more, please see Bakhshian et al., ADWR, 2019.




2.1. Dynamics of Counter-Current Imbibition in Fractured Rocks

Imbibition which is a process of displacing a non-wetting fluid by a wetting fluid in porous media is of great interest in applications including oil and gas recovery, geologic carbon sequestration, paper industry, and soil science. We study the dynamics of the counter-current imbibition in fractured rock samples with the application of CO2 geo-sequestration, as the rock matrix is saturated with CO2 and brine exists in the adjacent micro-fracture. When employing the lattice Boltzmann model for two-phase flow simulations, we examine the matrix-fracture interaction by performing spontaneous and forced imbibition tests.

The corresponding publication is coming out soon ….



3- Reactive Transport in Porous Media

CO2 enriched brine interaction with reservoir minerals and the subsequent mineral trapping of CO2 alters the morphology of pore structure. Such changes in the pore space modify the storage capacity of reservoirs and increase the long-term security of CO2 storage. The extent of pore space modification depends on the relative weight of advection, diffusion, and reaction mechanisms. We present a general framework for direct simulation of reactive transport in digitized reservoir rock samples based on pore-scale modeling in 2D and 3D pore throat networks. We implement a modified version of the marker-based watershed segmentation to extract the pore-network of 3D micro-CT scan images. The extracted network is used to simulate the reactive solute transport and dissolution on real rock samples. We implement our approach to study the CO2 injection in the Cranfield site, Mississippi, USA.

To learn more, please see Dashtian et al., Comput. Geosci., 2019.


4- Simulation of Adsorption-induced Deformation in Porous Media

Swelling of porous materials due to their liquid content, or by storage of gases in their pore space, is a widespread phenomenon. In this study, I proposed a novel framework by coupling the lattice gas density functional theory (DFT) coupled with the equation for elastic deformation and finite-element (FE) computations to study adsorption-induced deformation in disordered porous media.


4.a- Adsorption-induced Structural Deformation in Metal-Organic Frameworks (MOFs)

Metal-organic frameworks (MOFs) have recently attracted considerable attention as new nanoporous materials with applications to the separation of fluid mixtures, catalysis, gas capture and storage, and drug delivery. A subclass of MOFs, the MIL-53 family, exhibits a complex structural phase transition, often referred to as the breathing transition, which occurs when gas molecules are adsorbed in its pore space. In this phenomenon, the material morphology oscillates between two distinct phases, usually referred to as the narrow-pore (np) and large-pore (lp) phases. In this study, I describe a statistical mechanical model based on the energetics of the system that couples the adsorbates with the host framework and the ensuing structural deformation of the materials. The model is used to study the adsorption of CO2 and CH4 in MOF frameworks.

To learn more, please see Bakhshian et al., JPCC, 2018.


4.b- Gas Adsorption and Deformation in Geological Formations

One example of adsorption-induced deformation is swelling of coal seams and shale formations upon gas adsorption during the storage of CO2 and enhanced recovery of coalbed methane. Although the deformation is very small, the associated stresses may mount up to high values and induce large external forces on the formations. Moreover, adsorption-induced swelling of underground formations has been identified as one of the main factors that affect porosity, permeability,  diffusivity, and surface area of the pore space. Due to the importance of this phenomenon in the oil and gas industry, it is imperative to understand how microstructural, flow, and transport properties of a formation vary in response to the mechanical deformation.

To learn more, please see Bakhshian et al., Int. J. Greenhouse Gas Control, 2017, and,  Bakhshian et al., Sci. Rep., 2018.



5- Dynamics of Slip Weakening in Granular Gouge

Using Discrete Element Method (DEM), I model shear strength loss at frictional asperity contacts induced by flash heating or flash weakening in granular gouge. I developed a parallelized DEM code using the OpenMP framework. I assess the shear response of the granular medium to different sliding velocities. Variation of local friction coefficient in the medium and evolution of frictional strength which is induced by slip weakening, has been investigated.