The method of characteristics applied to oil displacement by foam

Document Type

Conference Proceeding

Publication Date

1-1-2009

Abstract

Method of characteristics (MOC) provides key insights into complex foam enhanced oil recovery (EOR) displacements and the simulators that represent them. Most applications of MOC to foam have excluded oil. We extend MOC to foam flow with oil, where foam might be weakened or destroyed by oil saturations above a critical oil saturation and/or weakened or destroyed at low water saturations, as seen in experiments and represented in foam simulators. Simulators account for the effects of oil and capillary pressure on foam using algorithms that bring foam strength to zero as a function of oil or water saturation, respectively. Different simulators use different algorithms to accomplish this. We examine SAG (surfactant-alternating-gas) and continuous foam injection (process of co-injection of gas and surfactant solution) processes in one dimension (1D), using both MOC and numerical simulation. We find that the way simulators express the negative effect of oil or water saturation on foam can have a large impact on the nature of the displacement. For instance, for gas injection in a SAG process, if oil is assumed to completely destroy foam above some critical saturation, and initial oil saturation is above that value, foam has nearly no effect on the displacement. On the other hand, if oil saturation weakens foam abruptly but smoothly, then successful mobility control is possible. The resulting displacements can be complex. One may observe, for instance, foam propagation predicted at residual water saturation, with zero flow of water. In other cases, the displacement jumps in a shock past the entire range of conditions in which foam forms. We examine the sensitivity of the displacement to initial oil and water saturations in the reservoir, the fraction of water in the injected foam and the functional forms used to express foam sensitivity to oil and water saturations. Copyright 2009, European Association of Geoscientists and Engineers.

Publication Source (Journal or Book title)

71st European Association of Geoscientists and Engineers Conference and Exhibition 2009: Balancing Global Resources. Incorporating SPE EUROPEC 2009

First Page

1370

Last Page

1391

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