A Novel Multirate Dual-Porosity Model for Improved Simulation of Fractured and Multiporosity Reservoirs

Abstract

A major part of the world's remaining oil reserves is in fractured carbonate reservoirs, which are dual-porosity (fracture-matrix) or multiporosity (fracture/vug/matrix) in nature. Fractured reservoirs suffer from poor recovery, high water cut, and generally low performance. They are modeled commonly by use of a dual-porosity approach, which assumes that the high-permeability fractures are mobile and low-permeability matrix is immobile. A single transfer function models the rate at which hydrocarbons migrate from the matrix into the fractures. As shown in many numerical, laboratory, and field experiments, a wide range of transfer rates occurs between the immobile matrix and mobile fractures. These arise, for example, from the different sizes of matrix blocks (yielding a distribution of shape factors), different porosity types, or the inhomogeneous distribution of saturations in the matrix blocks. Thus, accurate models are needed that capture all the transfer rates between immobile matrix and mobile fracture domains, particularly to predict late-time recovery more reliably when the water cut is already high. In this work, we propose a novel multi-rate mass-transfer (MRMT) model for two-phase flow, which accounts for viscous-dominated flow in the fracture domain and capillary flow in the matrix domain. It extends the classical (i.e., singlerate) dual-porosity model to allow us to simulate the wide range of transfer rates occurring in naturally fractured multiporosity rocks. We demonstrate, by use of numerical simulations of waterflooding in naturally fractured rock masses at the gridblock scale, that our MRMT model matches the observed recovery curves more accurately compared with the classical dual-porosity model. We further discuss how our multi-rate dual-porosity model can be parameterized in a predictive manner and how the model could be used to complement traditional commercial reservoir-simulation workflows.

Simulation of chemical reaction localization using a multi-porosity reactive transport approach

“…The most widely used are the Multi-Rate Mass Transfer (MRMT) and Continuous Time Random Walk (CTRW). MRMT is a non-local in time continuous formulation that simulates mass transfer between a mobile and multiple immobile regions by diffusive or first-order mass transfer terms (Benson and Meerschaert, 2009;Carrera et al, 1998;Donado et al, 2009;Fernandez-Garcia and Sanchez-Vila, 2015;Geiger et al, 2013;Gouze et al, 2008;Haggerty and Gorelick, 1995;Haggerty et al, 2000;Roth and Jury, 1993;Wang et al, 2005;Willmann et al, 2010;Zhang et al, 2007). Models similar to MRMT exist for diffusion from a fracture into the matrix of the rock (Cvetkovic et al, 1999;Gerke and van Genuchten, 1996;Grisak and Pickens, 1980;Małoszewski and Zuber, 1985;Moreno and Neretnieks, 1993;Shapiro, 2001).…”

3D non-conforming mesh model for flow in fractured porous media using Lagrange multipliers

“…First, the implementation of the LM-L 2 method is tested by comparing the obtained results to 2D benchmark results presented by Flemisch et al [20]. Benchmark 1, which was first introduced by Geiger et al [24], is chosen as a representative example for this study. Emphasis is placed on the validation of the presented method with reference results from Geiger et al [24], Flemisch et al [20], while results of alternative approaches can be found in the listed references.…”

Convective‐Reactive CO2 Dissolution in Aquifers With Mass Transfer With Immobile Water

“…Having a pure calcium carbonate system with no chemical heterogeneity, the partitioning of the porous medium is only due to the physical heterogeneity at pore scale (fracture/matrix), and therefore, no localization of reactions is assumed. We consider one immobile zone only, to align the formulation with the time‐dependent single‐rate mass transfer model as opposed to multiple rate mass transfer model where multiple mass transfer processes occur simultaneously in a porous medium (see, e.g., Fernandez‐Garcia & Sanchez‐Vila, ; Geiger et al, ; Maier et al, ; Soler‐Sagarra et al, ; Tecklenburg et al, ). As such equation (3) can be rewritten as …”

“…Having a pure calcium carbonate system with no chemical heterogeneity, the partitioning of the porous medium is only due to the physical heterogeneity at pore scale (fracture/matrix), and therefore, no localization of reactions is assumed. We consider one immobile zone only, to align the formulation with the time-dependent singlerate mass transfer model as opposed to multiple rate mass transfer model where multiple mass transfer processes occur simultaneously in a porous medium (see, e.g., Fernandez-Garcia & Sanchez-Vila, 2015; Geiger et al, 2013;Maier et al, 2013;Soler-Sagarra et al, 2016;Tecklenburg et al, 2016). As such equation (3) can be rewritten as…”