Modelling the effect of oil on foam with the wave curve method

Enhanced oil recovery by gas injection can show excellent displacement efficiency but may suffer from poor sweep efficiency. A promising method to overcome poor sweep efficiency in gas-injection enhanced oil recovery processes is foam injection. The effect of oil saturation on foam stability is complicated and not fully understood. Complexity in foam models give rise to numerical problems in three-phase simulations with foam. The objective of this thesis is to study foam displacement with fractional-flow theory instead of simulation. Results are expected to be unaffected by numerical problems. Fractional-flow theory is a strong analytical tool which can greatly enhance the understanding of displacement of fluids initially in the reservoir by injected fluid. In this study we use fractional-flow theory to describe foam displacement in the presence of oil in a 1-D reservoir model. Fractional-flow theory for displacement with three immiscible phases has increased complexity compared to fractional-flow theory for displacement with two phases. The wave curve method solves fractional-flow problems with three immiscible phases based on shock waves, rarefaction waves and areas of constant state. RPN, developed at the Instituto Nacional de Matemática Pura e Aplicada, develops solutions to three-phase fractional-flow problems based on the wave curve method. The software package is used to enhance understanding of foam displacement. In this study we succesfully couple STARSTM interpolation parameters for foam displacement to RPN. Unlike simulators, RPN is an analytical tool which should be insensitive to numerical artifacts. Practical results obtained from the software include a catalog of displacement cases with initial and injection conditions either inside or outside the foam region. Next, a challenging scenario of Namdar Zanganeh (2011), where simulation yields unsatisfactory results, is addressed with RPN. An approximation of this scenario showed similar numerical artifacts in simulation, RPN provides well-behaved solutions. Thirdly, an analysis is done on the formation of an oil bank ahead of the foam front with an oil saturation that could possible lead to foam collapse. This study shows that the oil saturation in the oil bank never exceeds the saturation where oil leads to foam collapse.

Subject

enhanced oil recovery
reservoir engineering
foam
modelling

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Student theses

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master thesis

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