Accounting for poro-mechanical effects in full-field reservoir simulation studies and uncertainty quantification workflows using complex reservoir models is challenging, mainly because of the high computational cost. We hence introduce an alternative approach that couples hydrodynamics through existing flow diagnostics simulations with poro-mechanics to screen the impact of coupled poro-mechanical processes on reservoir performance without significantly increasing computational overheads. In flow diagnostics, time-of-flight distributions and influence regions can be used to characterise the flow field in the reservoir, which depends on the distribution of petrophysical properties that are altered due to production-induced changes in pore pressure and effective stress. These extended flow diagnostics calculations hence enable us to quickly screen how the dynamics in the reservoirs (e.g. reservoir connectivity, displacement efficiency, and well allocation factors) are affected by the complex interactions between poro-mechanics and hydrodynamics. Our poro-mechanically informed flow diagnostics account for steady-state and single-phase flow conditions based on the poro-elastic theory and assume that the reservoir does not contain fractures. Fluid flow and rock deformation calculations are coupled sequentially. The equations are discretised using a finite-volume method with two-point flux-approximation and the virtual element method, respectively. The solution of the coupled system considers stress-dependent permeabilities. Due to the steady-state nature of the calculations and the effective proposed coupling strategy, these calculations remain computationally efficient while providing first-order approximations of the interplay between poro-mechanics and hydrodynamics, as we demonstrate through a series of case studies. The extended flow diagnostic approach hence provides an efficient complement to traditional reservoir simulation and uncertainty quantification workflows and enable us to assess a broader range of reservoir uncertainties.@en

Hydro-mechanical coupling is imperative when the stress disturbances induced by production/injection processes affect the reservoir performance. However, the application of coupled hydro-mechanical models in actual fullfield studies is still limited, mainly because of the high computational cost. Despite the existence of simplified coupling strategies (one-way coupling and loose coupling) that reduce the computational cost, numerical simulations remain challenging because of the significant computing time required to simulate coupled processes in complex and heterogeneous reservoir models. With the appropriate extension, flow diagnostics could also be used to screen and assess the impact of hydro-mechanical processes on reservoir performance so as to select a smaller number of models for detailed, and computationally costly, fully coupled hydro-mechanical simulations. We hence present an approach that allows us to extend the existing flow diagnostics to account for geomechanical effects without increasing the computational overhead significantly. Flow diagnostics approximate the dynamic reservoir behaviour in seconds by computing the time of flight and steady-state tracer distributions directly on the reservoir grid. Hence, the extended flow diagnostics simulations complement full-physics simulations for estimating reservoir connectivity, fluid-fronts distributions, fluid displacement efficiency and well allocation factors under geomechanical effect. The acceleration of the proposed hydro-mechanical coupling is achieved by: 1) the representation of the dynamic behaviour through the use of flow diagnostics simulations (Møyner et al., 2014); 2) the formulation of the hydromechanical problem to account for steady-state conditions based on poro-elastic theory (Coussy, 1994, 2004); 3) a sequential stress-flow coupling using stress-dependent permeability as a coupling term. This coupling strategy ensures stability and fast convergence of the hydro-mechanical solution using a stress-fixed split strategy (Kim et al., 2011a, 2011b) and yields a significant reduction of the CPU time. Two cases studies were analysed based on the SPE 10 Model (Christie and Blunt, 2001) in which the effect of a 5-spot injection pattern subjected to a gravity load is studied, and the effect of mechanical heterogeneity is considered. These examples demonstrate the application of the proposed methodology to assess geomechanical impact in highly heterogeneous formations and the importance of not only account for petrophysical heterogeneities when assessing reservoir performance but also for the heterogeneity of mechanical properties as these alter the petrophysical properties when stress-sensitive reservoirs are produced. Geomechanically informed flow diagnostics account for coupled hydro-mechanical effects that can alter the performance of stress-sensitive reservoirs during production.

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