Multiphysics and Multiscale Methods for Modeling Fluid Flow Through Naturally Fractured Vuggy Carbonate Reservoirs

Abstract

We present a novel approach for flow simulations through naturally-fractured vuggy carbonate reservoirs. This approach generalizes upscaling methods which have been successfully used to perform reservoir simulations on geological (fine) scales. Typically, vugular porous media is described using both Stokes and Darcy's equations at the fine-scale. We propose the use of simplified model based on StokesBrinkman equations. Stokes and Darcy equations can be obtained from these equations by appropriate choice of parameters. Moreover, in the presence of damaged zones between vugular regions and Darcy regions, Stokes-Brinkman equations allow a seamless transition.The upscaling of fine-scale equations is addressed within homogenization theory. Appropriate local problems are solved to compute the effective permeabilities, which are further used for the simulations on the field scale. We present numerical results for homogeneous and heterogeneous background permeability fields. Our results show that the coarse-scale permeability field is greatly affected when the background permeability is heterogeneous. This is due to the fact that the high flow channels connecting some of the vugs significantly alter the upscaled permeability. We compare the coarse-scale pressure obtained from upscaled equations with the averaged fine-scale pressure. The results are in agreement which indicates that the upscaled models are accurate for practical purposes.

The digital rock analysis of biogenically induced reservoir heterogeneities in Cretaceous reservoirs of Saudi Arabia

“…Darcy's model is to approximate pressure and fluxes on a coarse grid in large-scale discontinuities, whereas fine-scale effects are captured through basis functions computed numerically by solving local Stokes-Brinkman flow problems on the underlying fine-scale geocellular grid. The Stokes-Brinkman equations give a unified approach to simulating free-flow and porous regions using a single system of equations, they avoid explicit interface modeling, and reduce to Darcy or Stokes flow in certain parameter limits [3]. The modeling demonstrates how fine-scale flow in bioturbated pore networks can be represented within a coarse-scale Darcy-flow model in fractures of the burrow to matrix interface and multi-scale elements.…”

Residual oil distribution characteristic of fractured-cavity carbonate reservoir after water flooding and enhanced oil recovery by N2 flooding of fractured-cavity carbonate reservoir

“…Strong heterogeneity of reservoir, complex structure of reservoir space and oil/water flow relationship is main characteristics of fractured-cavity carbonate reservoir. Moreover the main storage space and seepage path possesses the features of discontinuous and random distributions of fractures (width in millimeter level) and caves (diameter in meter level), big scale difference of caves and large dip angle of fractures (Popov et al, 2007;Lu et al, 2010;Chen et al, 2010). With the development, many shortcomings such as short period of stable production, early water breakthrough, fast increasing of water cut, high natural decline rate and low degree of development are exposed gradually.…”

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