Pore-to-core simulations of flow with large velocities using continuum models and imaging data

We consider computational modeling of flow with small and large velocities at porescale and at corescale, and we address various challenges in simulation, upscaling, and modeling. While our focus is on voxel-based data sets from real porous media imaging, our methodology is verified first on synthetic geometries, and we analyze various scaling and convergence properties. We show that the choice of a voxel-based grid and REV size can lead up to 10-20% difference in calculated conductivities. On the other hand, the conductivities decrease significantly with flow rates, starting in a regime usually associated with the onset of inertia effects. This is accompanied by deteriorating porescale solver performance, and we continue our experiments up until about 50% reduction in conductivities, i.e., to Reynolds number just under 1. To account for this decrease, we propose a practical power-based fully anisotropic non-Darcy model at corescale for which we calculate the parameters by upscaling.Keywords: Upscaling, Inertia effects, Anisotropy, Forchheimer model, Flow in porous media, 76S05, 76M45, Navier–Stokes equations, Convergence, Porescale simulations, 76M50, Non-Darcy flo

Computational upscaling of inertia effects from porescale to mesoscale

This paper is included in the Proceedings, Part 1, of the International Conference on Computational Science 2009 (ICCS 2009) held in Baton Rouge, LA, USA, May 25-27, 2009.We propose algorithms for computational upscaling of flow from porescale (microscale) to lab scale (mesoscale). In particular, we solve Navier-Stokes equations in complex pore geometries and average their solutions to derive properties of flow relevant at lab scale such as permeability and inertia coefficients. We discuss two variants of tra-ditional discretizations: a simple algorithm which works well in periodic isotropic media and can be used when coarse approximations are needed, and a more complex one which is well suited for nonisotropic geometries. Convergence of solutions and averaging techniques are major concerns but these can be relaxed if only mesoscopic parameters are needed. The project is a proof-of-concept computational laboratory for porous me-dia which delivers data needed for mesoscale simulations by performing microscale computational simulations

Modeling non-Darcy flows in realistic pore-scale proppant geometries

The ability to evaluate the effective permeability of proppant packs is useful in predicting the efficiency of hydraulic fracture installations. In this paper we propose a computational approach combining microimaging data from X-ray computed microtomography, the simulations of flow at pore-scale, and an upscaling process which identifies the effective model parameters at the core-scale. With this computational approach applied to proppant pack we confirm the reduction in the fracture conductivity and subsequent reduction in the productivity of a hydraulically fractured reservoir due to the high flow rates and to the migration of fine particles resulting in pore throat bridging

Darcy’s and Forchheimer’s laws in practice. Part 2. The numerical model

Our study is based on a column experiment of water flow through a porous granular bed. In Part 1 we propose eight methods to derive parameters of flow models based on measurement data. These parameters are permeability and Forchheimer coefficient for Darcy’s and Forchheimer’s laws. The approach presented in this part uses two numerical models to perform simulations of flow. One model is based on the Finite Element Method implemented in the authors’ code. The second model, which is ANSYS/Fluent package, uses the Finite Volume Method. Results of numerical computations are compared with experimental data that allows determination of the best method of parameter evaluation (in which the error was less than 3% over the whole range of filtration velocities). The problem of identification of ranges of applicability of the Darcy’s and Forchheimer’s laws is also addressed. In the conclusions, a set of guidelines is given, which should facilitate planning a similar experiment and its computational processing

Discretisation of Thermal Diffusion Equation in Multilayer Structures with Variable Material Parameters and Different Thicknesses

The paper presents details of discretisation of a thermal diffusion equation in one-dimensional space in terms of the Finite Volume Method. In the following sections, the method of space discretisation is discussed along with the approximation of a spatial derivative, matrix notation of a system of equations, special cases, approximation of three types of boundary conditions and derivative approximation over time. Much attention is also given to the issue of averaging material properties which can generally be different in adjacent cells.The study aims to analyse various multilayer structures for their suitability as heat storage. The launch of studies described in the paper has been driven by the lack of methods for effective heat storage, which is currently one of the key problems faced by the renewable energy industry

Darcy’s and Forchheimer’s laws in practice. Part 1. The experiment

The aim of this study is to derive flow parameters, which are permeability and Forchheimer coefficient, based on experimentally measured flow rates and pressure drops. When flow rates used in measurements exceed the limits of linear Darcy’s flow regime we discuss what needs to be taken into account while processing the measurements. The study consists of two parts. In this part we briefly recall Darcy’s and Forchheimer’s laws and address the issue of detecting transition between ranges of their applicability. Then we describe the experiment and discuss 8 different ways to process measurement data, four for Darcy’s, and four for Forchheimer’s models. The main topic of the second part is to provide recommendations for the best ways to process data, so that the results obtained with numerical models are in the best agreement with the experimental data. The results shown in the two papers belong to a larger work devoted to modeling fluid flows through porous media, with a special interest in granular beds