Combining Geomechanics with Multi-Phase Flow Simulations in Naturally Fractured Reservoirs
Geomechanics plays a very important role in understanding and predicting the behaviour of naturally fractured reservoirs (NFRs) where most of the flow occurs through the fractures. Conceptually, the reservoir is composed of two domains: a flowing high permeability region representing the fracture network; and a stagnant low permeability region that represents the rock matrix. The interaction between the fractures and the surrounding permeable matrix and the orientation of conductive fractures and faults with respect to far-field stress field is crucially important. In order to develop the predictive capability of the physical phenomena that occur in NFRs including compaction related to production, reservoir subsidence, induced fracturing, reactivation of pre-existing fractures and faults, the interaction between rock matrix and the fractures, it is necessary to couple reservoir simulations with geomechanics.
In this study, we present a novel approach which considers both the static and dynamic behaviour of the fracture network based on length, orientation and their spatial distribution. For simulating single phase and multiphase flow simulations, we use combined Finite Element - Finite Volume Method (FEM-FVM) in which the pressure equation is solved using the finite-element method and the transport equation using finite-volume method. For capturing the dynamics of the fractured system, we apply Combined Finite-Discrete Element Method (FEM/DEM) with combined single and smeared crack model, that has the advantages of both continuum and discontinuum techniques to simulate intact behaviour, the initiation and propagation of new fractures, and reactivation of pre-existing fractures. We use realistic fracture geometries to compare changes in the static and dynamic behaviour by varying the magnitude and orientation of far-field stresses and boundaries conditions.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009