Multiporosity Flow in Fractured Low-Permeability Rocks

TL;DR

This paper introduces a flexible multiporosity flow model for fractured low-permeability rocks, extending classical models to better simulate complex flow behaviors with multiple rock matrix continua.

Contribution

It develops a general multiporosity model adapting multirate solute transport concepts to viscous flow, incorporating multiple rock matrix continua with probabilistic exchange coefficients.

Findings

The model can simulate double and triple porosity flow behaviors.

Semi-analytical solutions demonstrate the model's versatility.

The approach is conceptually simple yet highly flexible.

Abstract

A multiporosity extension of classical double and triple porosity fractured rock flow models for slightly compressible fluids is presented. The multiporosity model is an adaptation of the multirate solute transport model of Haggerty and Gorelick (1995) to viscous flow in fractured rock reservoirs. It is a generalization of both pseudo-steady-state and transient interporosity flow double porosity models. The model includes a fracture continuum and an overlapping distribution of multiple rock matrix continua, whose fracture-matrix exchange coefficients are specified through a discrete probability mass function. Semi-analytical cylindrically symmetric solutions to the multiporosity mathematical model are developed using the Laplace transform to illustrate its behavior. The multiporosity model presented here is conceptually simple, yet flexible enough to simulate common conceptualizations of double and triple porosity flow. This combination of generality and simplicity makes the multiporosity model a good choice for flow in low-permeability fractured rocks.