Displacement theory and numerical simulation of hybrid gas/chemical EOR processes

Mehrabi, Mehran
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Hybrid gas/chemical enhanced oil recovery (EOR) techniques comprises gas and chemicals such as surfactant to improve oil recovery by improvement in displacement and/or sweep efficiencies. Design and modeling of these processes are challenging due to the inherent complexities of phenomena that may occur simultaneously. For example, in low-tension gas (LTG) flooding we inject gas and water with at least two types of surfactants, one as a foaming agent and another as a low-IFT agent. In this process, we may have the simultaneous flow of the four phases of water, oil, gas, and microemulsion. The gas phase may flow partly as foam and partly as free gas. Proper modeling of the foam flow, the phase behavior between the oil and gas, the phase behavior between the water, oil, and microemulsion and the interaction between different phases and their rheology and petrophysical properties are among the challenges of understanding and modeling this process.

In this study we develop models, techniques and reservoir simulation codes to investigate different aspects of hybrid gas/chemical EOR processes. In this regard, we study the following subjects: 1) estimation of the parameters of foam models and the effect of porosity and permeability on the apparent viscosity of foam in porous media, 2) development of an algorithm for finding classical solutions to Riemann problems of three-phase flow of gas/foam, water, and oil, 3) development of a displacement theory for LTG flooding, and 4) development and implementation of a chemical-compositional model in an implicit pressure explicit concentration (IMPEC) reservoir simulator.

The developed models and simulation codes can help engineers and practitioners with both the design and large scale simulation of hybrid gas/chemical processes.