7,688 research outputs found
A continuum model of multi-phase reactive transport in igneous systems
Multi-phase reactive transport processes are ubiquitous in igneous systems. A
challenging aspect of modelling igneous phenomena is that they range from
solid-dominated porous to liquid-dominated suspension flows and therefore
entail a wide spectrum of rheological conditions, flow speeds, and length
scales. Most previous models have been restricted to the two-phase limits of
porous melt transport in deforming, partially molten rock and crystal settling
in convecting magma bodies. The goal of this paper is to develop a framework
that can capture igneous system from source to surface at all phase proportions
including not only rock and melt but also an exsolved volatile phase. Here, we
derive an n-phase reactive transport model building on the concepts of Mixture
Theory, along with principles of Rational Thermodynamics and procedures of
Non-equilibrium Thermodynamics. Our model operates at the macroscopic system
scale and requires constitutive relations for fluxes within and transfers
between phases, which are the processes that together give rise to reactive
transport phenomena. We introduce a phase- and process-wise symmetrical
formulation for fluxes and transfers of entropy, mass, momentum, and volume,
and propose phenomenological coefficient closures that determine how fluxes and
transfers respond to mechanical and thermodynamic forces. Finally, we
demonstrate that the known limits of two-phase porous and suspension flow
emerge as special cases of our general model and discuss some ramifications for
modelling pertinent two- and three-phase flow problems in igneous systems.Comment: Revised preprint submitted for peer-reviewed publication: main text
with 8 figures, 1 table; appendix with 3 figures and 2 table
Finite element analysis of non-isothermal multiphase porous media in dynamics
This work presents a mathematical and a numerical model for the analysis of the
thermo-hydro-mechanical (THM) behavior of multiphase deformable porous materials
in dynamics. The fully coupled governing equations are developed within the
Hybrid Mixture Theory. To analyze the THM behavior of soil structures in the low
frequency domain, e.g. under earthquake excitation, the u-p-T formulation is advocated
by neglecting the relative acceleration of the fluids and their convective terms.
The standard Bubnov-Galerkin method is applied to the governing equations for the
spatial discretization, whereas the generalized Newmark scheme is used for the time
discretization. The final non-linear and coupled system of algebraic equations is
solved by the Newton method within the monolithic approach. The formulation and
the implemented solution procedure are validated through the comparison with
other finite element solutions or analytical solutions
A GPU-accelerated package for simulation of flow in nanoporous source rocks with many-body dissipative particle dynamics
Mesoscopic simulations of hydrocarbon flow in source shales are challenging,
in part due to the heterogeneous shale pores with sizes ranging from a few
nanometers to a few micrometers. Additionally, the sub-continuum fluid-fluid
and fluid-solid interactions in nano- to micro-scale shale pores, which are
physically and chemically sophisticated, must be captured. To address those
challenges, we present a GPU-accelerated package for simulation of flow in
nano- to micro-pore networks with a many-body dissipative particle dynamics
(mDPD) mesoscale model. Based on a fully distributed parallel paradigm, the
code offloads all intensive workloads on GPUs. Other advancements, such as
smart particle packing and no-slip boundary condition in complex pore
geometries, are also implemented for the construction and the simulation of the
realistic shale pores from 3D nanometer-resolution stack images. Our code is
validated for accuracy and compared against the CPU counterpart for speedup. In
our benchmark tests, the code delivers nearly perfect strong scaling and weak
scaling (with up to 512 million particles) on up to 512 K20X GPUs on Oak Ridge
National Laboratory's (ORNL) Titan supercomputer. Moreover, a single-GPU
benchmark on ORNL's SummitDev and IBM's AC922 suggests that the host-to-device
NVLink can boost performance over PCIe by a remarkable 40\%. Lastly, we
demonstrate, through a flow simulation in realistic shale pores, that the CPU
counterpart requires 840 Power9 cores to rival the performance delivered by our
package with four V100 GPUs on ORNL's Summit architecture. This simulation
package enables quick-turnaround and high-throughput mesoscopic numerical
simulations for investigating complex flow phenomena in nano- to micro-porous
rocks with realistic pore geometries
The XDEM Multi-physics and Multi-scale Simulation Technology: Review on DEM-CFD Coupling, Methodology and Engineering Applications
The XDEM multi-physics and multi-scale simulation platform roots in the Ex-
tended Discrete Element Method (XDEM) and is being developed at the In- stitute
of Computational Engineering at the University of Luxembourg. The platform is
an advanced multi- physics simulation technology that combines flexibility and
versatility to establish the next generation of multi-physics and multi-scale
simulation tools. For this purpose the simulation framework relies on coupling
various predictive tools based on both an Eulerian and Lagrangian approach.
Eulerian approaches represent the wide field of continuum models while the
Lagrange approach is perfectly suited to characterise discrete phases. Thus,
continuum models include classical simulation tools such as Computa- tional
Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended
configuration of the classical Discrete Element Method (DEM) addresses the
discrete e.g. particulate phase. Apart from predicting the trajectories of
individual particles, XDEM extends the application to estimating the thermo-
dynamic state of each particle by advanced and optimised algorithms. The
thermodynamic state may include temperature and species distributions due to
chemical reaction and external heat sources. Hence, coupling these extended
features with either CFD or FEA opens up a wide range of applications as
diverse as pharmaceutical industry e.g. drug production, agriculture food and
processing industry, mining, construction and agricultural machinery, metals
manufacturing, energy production and systems biology
Sedimentation and Flow Through Porous Media: Simulating Dynamically Coupled Discrete and Continuum Phases
We describe a method to address efficiently problems of two-phase flow in the
regime of low particle Reynolds number and negligible Brownian motion. One of
the phases is an incompressible continuous fluid and the other a discrete
particulate phase which we simulate by following the motion of single
particles. Interactions between the phases are taken into account using locally
defined drag forces. We apply our method to the problem of flow through random
media at high porosity where we find good agreement to theoretical expectations
for the functional dependence of the pressure drop on the solid volume
fraction. We undertake further validations on systems undergoing gravity
induced sedimentation.Comment: 22 pages REVTEX, figures separately in uudecoded, compressed
postscript format - alternatively e-mail '[email protected]' for
hardcopies
Microfluidic Pore Model Study on Physical and Geomechanical Factors Influencing Fluid Flow Behavior in Porous Media
Fluid flow in porous media is a subject of fundamental importance and relevant to numerous engineering applications. The comprehensive description of fluid interaction parameters containing wetting properties, fluid-fluid displacement ratio, and capillary pressure, are inevitably needed. Moreover, the fine-grained sedimentsā response to various pore fluids and migration in porous media influences reservoir geomechanical properties and pore clogging is essential to a better understanding of fluids flow behavior.
This dissertation provides a detailed study of physical and geomechanical factors influencing fluids flow behavior in porous media. The two-dimensional micromodel tests have been conducted under a wide selection of fluids flow conditions. The experiments combined with pore network modeling are added to predict the fluid-fluid displacement ratio and capillary curves regarding different fluids. The finesā geomechanical properties such as electrical sensitivity, compressibility, and hydraulic conductivity, together with pore plugging criteria are measured through various experiments including sedimentation, electrical sensitivity, and consolidation tests.
Results of this research show that increase in injection fluid velocity, viscosity, contact angle, and a decrease in fluidās interfacial tension can result in higher viscosity and capillary numbers, which leads to an improvement of the fluid-fluid displacement ratio in porous media. Experiments with the subsequently conducted simulation corroborate a higher capillary pressure is expected with a decrease in contact angle and an increase in interfacial tension. Meanwhile, estimation of capillary pressure can be achieved with measured fluidsā wetting properties at different stress levels. Besides, the findings indicate that fine sedimentsā geomechanical properties and clogging criteria can be altered due to finesā response to distinct pore fluids. The geomechanical properties of the different fine sediments also vary with pore fluid chemistry changes. And, fines clogging in porous media is observed under conditions of a lower pore throat width/fine size ratio, a higher fine concentration, a relatively higher flow rate, and the changed pore fluids. Additionally, the presence of a moving gas/liquid meniscus increases the fines clogging potential. In summary, an understanding of fluidsā physical and geomechanical properties, in addition to an identification of fines influences, can help to evaluate the performance of fluids flow in porous media
Advances and challenges in shale oil development: A critical review
Ā Ā Ā Ā Different from the conventional oil reservoirs, the primary storage space of shale is micro/nano pore networks. Moreover, the multiscale and multi-minerals characteristics of shale also attract increasing attentions from researchers. In this work, the advances and challenges in the development of shale oil are summarized from following aspects: phase behavior, ļ¬ow mechanisms, reservoir numerical simulation and production optimization. The phase behavior of ļ¬uids conļ¬ned in shale nanopores are discussed on the basis of theoretical calculations, experiments, and molecular simulations. The ļ¬uid transport mechanisms through shale matrix are analyzed in terms of molecular dynamics, pore scale simulations, and experimental studies. The methods employed in fracture propagation simulation and production optimization of shale oil are also introduced. Clarifying the problems of current research and the need for future studies are conducive to promoting the scientiļ¬c and effective development of shale oil resources.Cited as: Feng, Q., Xu, S., Xing, X., Zhang, W., Wang, S. Advances and challenges in shale oil development: A critical review. Advances in Geo-Energy Research, 2020, 4(4),Ā 406-418, doi: 10.46690/ager.2020.04.0
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