Modeling of miscible CO2 foam displacements with oil

Modeling of miscible CO2 foam displacements with oil

Van der Heijden, T.L.M.

Rossen, W.R. (mentor)

Civil Engineering and Geosciences

2009-04-07

Fractional-flow theory provides key insights into complex foam IOR displacements and acts as a benchmark for foam simulators. In some cases with mobile oil present the process can be represented as a two-phase displacement. We examine two such cases. A first-contact miscible gas flood with foam injection includes a chemical shock defining the surfactant front and a miscible shock defining the gas front. The optimal water fraction for the foam (i.e., the water fraction that gives the fastest oil recovery) maintains the gas front slightly ahead of the foam (surfactant) front. A first-contact miscible foam process with surfactant dissolved in the (supercritical) CO2 is influenced by surfactant adsorption on rock and also on partitioning of the surfactant between water and CO2. A foam with surfactant that is more soluble in the water would propagate slowly, regardless of the surfactants absolute solubility or the level of adsorption on rock. This study forms part of a larger study combining fractional-flow modeling of these processes with computer simulation. The simulations verify the results obtained with fractional-flow methods and illustrate the challenges of accurate simulation of these processes. For both cases (i.e., first-contact miscible gas flood with foam injection, and first-contact miscible foam process with surfactant dissolved in the gas phase), simulations show that, in the limit of small grid blocks, the solution converges towards the fractional-flow solution. Fractional-flow theory not only predicts the displacement in the absence of dispersion, but helps explain the effects of dispersion on the displacement. Numerical dispersion introduced by the simulator is shown to have significant effects on the outcome of the simulations. At the urfactant front, numerical dispersion can drastically change the nature of the foam front, depending on the foam model used (specifically, the effect of surfactant concentration on foam strength). A foam model where foam is abruptly created at 50% of the injected surfactant concentration mitigates the effects of this dispersion, but the velocity of the foam bank is still altered. Investigation on the influence of adsorption shows that Langmuir-type adsorption models tend to sharpen up the (dispersed) surfactant front and are the least sensitive to dispersion. At the miscible front, dispersion affects mobilities in the oil and gas phase; again, fractional-flow theory helps explain the implications for the displacement. In multiple-contact (developed) miscible displacements, simulations, with dispersion present, show a region of three-phase flow ahead of the miscible front.

miscible co2-foam simulations

http://resolver.tudelft.nl/uuid:4d5fffa0-1c7f-4199-bfaa-31558381da03

TU Delft, Civil Engineering and Geosciences, Geotechnology

Student theses

master thesis

(c) 2009 T.L.M. van der Heijden