Verification and Proper Use of Water-Oil Transfer Function for Dual-Porosity and Dual-Permeability Reservoirs

Abstract

Accurate calculation of multiphase fluid transfer between the fracture and matrix in naturally fractured reservoirs is a very crucial issue. In this paper, we will present the viability of the use of a simple transfer function to accurately account for fluid exchange resulting from capillary and gravity forces between fracture and matrix in dual-porosity and dual-permeability numerical models. With this approach, fracture-and matrix-flow calculations can be decoupled and solved sequentially, improving the speed and ease of computation. In fact, the transfer-function equations can be used easily to calculate the expected oil recovery from a matrix block of any dimension without the use of a simulator or oil-recovery correlations.The study was accomplished by conducting a 3-D fine-grid simulation of a typical matrix block and comparing the results with those obtained through the use of a single-node simple transfer function for a water-oil system. This study was similar to a previous study (Alkandari 2002) we had conducted for a 1D gas-oil system.The transfer functions of this paper are specifically for the sugar-cube idealization of a matrix block, which can be extended to simulation of a match-stick idealization in reservoir modeling. The basic data required are: matrix capillary-pressure curves, densities of the flowing fluids, and matrix block dimensions.

Application of the two-stage Markov chain Monte Carlo method for characterization of fractured reservoirs using a surrogate flow model

“…We employ the dual-porosity, dual-permeability model for single-phase flow through a fractured porous medium, denoted by . This type of model first appeared in the sixties (see, e.g., [5,29]) and has continuously evolved since its initial introduction [1,4,19,25].…”

“…Nevertheless, in the interest of focusing our effort on developing the general MCMC framework for fractured reservoirs we will use the more traditional models in [1,4,19,25]. We expect that as our level of understanding matures, exchange of these models in achievable.…”

“…We note that shape factors and applicable shape factor coefficients are a topic in the previous research, and we refer the interested reader to [1,4,19,25,29] for details of extensive discussion on the proper use of transfer terms. We remark that more sophisticated flow scenarios require increasingly difficult transfer functions.…”

“…Most notably, discrete-fracture models allow for easier implementation of more sophisticated multi-component and multi-phase flow scenarios. Dual models, such as those found in [1,4], require an explicit definition of the matrix-fracture exchange term, which becomes increasingly difficult when generalized flow scenarios are considered. However, it is important to note that more sophisticated dual models derived on the basis of mathematical homogenization theory provide a more convenient approach for treating increasingly complicated flow scenarios [3,6,10].…”

A method for the estimation of dual transmissivities from slug tests

“…In general, a dual-permeability aquifer can be envisioned as a special type of dual-porosity reservoirs and should be defined as a medium composed of two subdomains, in which both are responsible for water flow. Fissuredporous rock-if water flow occurs through both (the fissures and the pores)-are classified as dual-permeability reservoirs, as are layered formations with layers of highly permeable sediments (Balogun et al 2009;Leij et al 2012). For example, two different sand layers or a layer of sand and a layer of fissured limestone or even one consolidated but fissured porous material like sandstone can fall under the definition of a dual-permeability medium.…”