Modified Random Walk-Particle Tracking method to model early time behavior of EOR and sequestration of CO2 in naturally fractured oil reservoirs

We modified the Random Walk-Particle Tracking (RW-PT) technique to simulate fully miscible CO2 injection, including matrix-fracture interaction, in naturally fractured oil reservoirs. After creating and validating the fracture network of a pilot test area for CO2 flooding, we first performed a sensitivity analysis and investigated the effect of different parameters (such as spacing between fractures and fracture lengths, fracture and matrix permeability, fracture-matrix interaction parameters, etc.) on the performance. Secondly, we performed a history match study to reproduce the observed CO2 production rate and achieved a good agreement between production and simulated data. We discussed the possibility of using the same technique to simulate the early stages of CO2 sequestration in naturally fractured reservoirs while injecting it for oil recovery. Although the introduced model does not capture the whole complexity of a miscible flow in fractured porous media due to its inherent characteristics, it can be used to estimate fully miscible transport processes in naturally fractured reservoirs, including CO2 flooding and the early stages of sequestration, as it has the capability of representing the complexity of natural fracture networks and matrix interaction. The simplifications used in the modeling and the limitations of the suggested technique are described as well. (C) 2015 Elsevier B.V. All rights reserved.