Page 54 - Principles of Applied Reservoir Simulation 2E

Chapter 5

Fluid Displacement

Fluid displacement processes require contact between the displacing fluid
and the displaced fluid. The movement of the interface between displacing and
displaced fluids and the breakthrough time associated with the production of
injected fluids at producing wells are indicators of sweep efficiency. This chapter
shows how to calculate such indicators using two analytical techniques: Buckley-
Leverett theory with Welge's method for immiscible fluid displacement, and
solution of the convection-dispersion equation for miscible fluid displacement.

5.1 Buckley-Leverett Theory

One of the simplest and most widely used methods of estimating the
advance of a fluid displacement front in an immiscible displacement process is
the Buckley-Leverett method. Buckley-Leverett Theory [1942] estimates the
rate at which an injected water bank moves through a porous medium. The
approach uses fractional flow theory and is based on the following assumptions:
• Flow is linear and horizontal
• Water is injected into an oil reservoir
• Oil and water are both incompressible
• Oil and water are immiscible
• Gravity and capillary pressure effects are negligible
The following analysis can be found in a variety of sources, such as Collins
[1961], Dake [1978], Wilhite [1986], and Craft, et al. [1991].

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