A critical review on coupled geomechanics and fluid flow in naturally fractured reservoirs

Abstract

Naturally fractured reservoirs have been a source of challenging issues with regard to field development, well stability, drilling, and enhanced oil recovery, as a connected fracture system can totally dominate the flow patterns. Because of the high degree of heterogeneity in flow characteristics and reservoir geomechanics, several mathematical, numerical and discretization methods are proposed to predict the hydrodynamics behaviour of naturally fractured reservoirs. This paper presents a critical review of the characteristics of naturally fractured reservoirs in terms of geomechanics and fluid flow. In the case of poorly connected fractures and high-density fractured networks, compared to the characteristic length of interest, multi-continuum approaches are widely applicable. The dual continuum approach can handle fracture matrix interaction implicitly much more conveniently than the Discrete Fracture Network (DFN) and Discrete Fracture Matrix (DFM) approaches, but it cannot capture the fracture geometry explicitly where the fracture is the main flow path in the area of interest. Distinct mathematical and numerical modelling of flow and reservoir geomechanics are also addressed in this review paper. In this context, various coupling schemes of reservoir geomechanics and fluid flow are discussed. Recent research challenges related to numerical modelling of multiphase flow, reservoir geomechanics, coupling schemes, and discretization are also reviewed. It is concluded that despite several research efforts, coupled geomechanics and multiphase flow is still a challenging issue related to mathematical, numerical models and discretization schemes to capture the hydrodynamic behaviour, such as fracture deformation and fluid flow behaviour, at fracture matrix interaction in naturally fractured reservoirs and adopting the best modelling approach is very much dependent on the desired hydro-mechanical aspects to be investigated.