Numerical analysis of pore scale processes in carbonate reservoirs from the Western Offshore basin in India

Reliable modelling of pore-scale network is critical to the understanding of fluid flow behaviour in a reservoir. This study presents the application of numerical techniques to high-resolution pore-network model derived from 3D micro-CT data obtained from scanning of core plugs of carbonate reservoirs from the Western Offshore basin. The methodology incorporates Direct Pore-Scale modelling, using computational fluid dynamics (CFD) techniques to solve flow field equations numerically, such as the Navier-Stokes equations. Adaptive mesh refinement within Finite Element Methods (FEM) and Finite Volume Methods (FVM) ensures accurate resolution of flow dynamics while maintaining numerical stability. Furthermore, the Lattice Boltzmann Method (LBM) is implemented to handle complex pore geometries and boundary conditions efficiently, with an advantage of large-scale parallelization to avoid interface tracking explicitly.

In parallel, Pore Network Models (PNMs) are integrated to represent pore spaces into simplified networks of pores and throats, preserving topological features for reconstructing the fabric of carbonate rock. These models are particularly effective to study collective behaviour across pores and complement direct methods by linking pore scale to sub-pore scale domain. Our approach addresses the computational intensity of sub-pore scale simulations and the limitations of network simplifications, that have implications on macroscopic properties such as Darcy-scale permeability for single-phase incompressible flows.

By integrating these approaches, we provide insights into accurate computation of mass fluxes and fluid-structure dynamics with high fidelity. Our results systematically analyse and compare numerical differences across methods to provide an understanding of the variability of computed properties, in our case single-phase incompressible absolute permeability. This facilitates in the resolution of complex fluid-structure dynamics and the development of optimized, stable, and consistent computational fluid dynamics (CFD) workflows for applications in enhanced hydrocarbon recovery and subsurface energy applications.