Thermo-viscous instability in thermal oil recovery of heavy crude oil

Steam injection and hot water flooding can be used to produce high viscosity oil that cannot be produced with standard oil recovery methods. The effectiveness of the injected oil-recovery fluid in displacing the oil is, however, strongly dependent on the stability of the interface between the injected fluid and the oil. If the interface between the two fluids becomes unstable, "fingers" of the injected fluid penetrate the oil instead of displacing the oil. This effect is known as "viscous fingering" and is difficult to predict with numerical reservoir simulations.

Thermo-viscous fingering occurs when a fluid is injected into a porous medium saturated with a fluid of different viscosity and temperature.

There are two propagating fronts, a fluid front which marks the interface between the two fluids and a thermal front where the temperature changes. Both fronts can become unstable, and they interact to form a complex stability problem. The interface between the two fluids is either an immiscible front, where capillary forces act, or a miscible front where diffusion mixes the two fluids. The thermal front, which moves slower than the fluid front, is always diffusive.

The aim of this project is to increase the understanding of thermo-viscous fingering in immiscible displacement. By studying immiscible displacement in simple geometries, we expect to learn how the rheological properties and temperatures of the fluids affect the stability of the interface, and thus the displacement efficiency. We will use a combination of analytical and numerical methods to find theoretical predictions for the stability of the interface.

In addition to being of interest as a fundamental fluid mechanics problem, we also believe that increased knowledge of thermo-viscous fingering can be important for the understanding and use of thermal oil recovery methods. A better understanding of how flow rate, temperature, viscosity, surface tension and permeability affect the stability of an immiscible displacement front, can hopefully lead to more efficient oil recovery strategies and improved sweep efficiency.