Multiporosity/multipermeability approach to the simulation of naturally fractured reservoirs

Abstract

This paper presents an array of deformation‐dependent flow models of various porosities and permeabilities relevant to the characterization of naturally fractured reservoirs. A unified multiporosity multipermeability formulation is proposed as a generalization of the porosity‐ or permeability‐oriented models of specific degree. Some new relationships are identified in the parametric investigation for both single‐porosity and dual‐porosity models. A formula is derived to express Skempton's constant B by Biot's coefficient H and relative compressibility ϕ*. It is found that the recovery of the original expression for Skempton's constant B is largely dependent on the choice of ϕ*, representing relative compressibility. The dual‐porosity/dual‐permeability model is evaluated through an alternative finite element approximation. The deformation‐dependent fracture flow mechanism is introduced where the rock matrix possesses low permeability and fracture flow is dominant. A preliminary study of the reservoir simulation identifies the strong coupling between the fluid flow and solid deformation.