Abstract
The ability of a novel nonionic CO2-soluble surfactant to propagate foam in porous media was compared with that of a conventional anionic surfactant (aqueous soluble only) through core floods with Berea sandstone cores. Both simultaneous and alternating injections have been tested. The novel foam outperforms the conventional one with respect to faster foam propagation and higher desaturation rate. Furthermore, the novel injection strategy, CO2 continuous injection with dissolved CO2-soluble surfactant, has been tested in the laboratory. Strong foam presented without delay. It is the first time the measured surfactant properties have been used to model foam transport on a field scale to extend our findings with the presence of gravity segregation. Different injection strategies have been tested under both constant rate and pressure constraints. It was showed that novel foam outperforms the conventional one in every scenario with much higher sweep efficiency and injectivity as well as more even pressure redistribution. Also, for this novel foam, it is not necessary that constant pressure injection is better, which has been concluded in previous literature for conventional foam. Furthermore, the novel injection strategy, CO2 continuous injection with dissolved CO2-soluble surfactant, gave the best performance, which could lower the injection and water treatment cost.
Highlights
Gases have been used as driving fluids in improved oil recovery processes since 1900 (Lake 1989), in which CO2 flooding has attracted a lot of attention because of its proven miscible-like displacement (Stalkup 1983), high availability, and environmental concerns
We chose 100 for fmmob, which is less than these employed by earlier researchers, such as 1000 (Rossen et al 2006), 3000 (Rossen and Shen 2007; Jamshidnezhad et al 2008a), or 5000 (Cheng et al 2000; Rossen and Renkema 2007; Kloet et al 2009), because we believe too strong foam used previously masked some details in the foam process, which is crucial for the novel foam
It was found that intermediate partition ability of the novel surfactant could significantly improve foam propagation owing to higher mobility of the gas phase than the aqueous phase
Summary
Gases have been used as driving fluids in improved oil recovery processes since 1900 (Lake 1989), in which CO2 flooding has attracted a lot of attention because of its proven miscible-like displacement (Stalkup 1983), high availability, and environmental concerns. Xing et al (2012) and McLendon et al (2014) measured the pressure drop across a Berea sandstone core as the CO2/surfactant solution was injected with selected branched ethoxylated CO2-soluble surfactants, which gave a weak foam with a mobility reduction factor around five. Through laboratory experiments and field scale simulations, in the current paper, we will peruse the following goals: demonstrate the remarkable advantages of CO2soluble surfactant on the laboratory scale with co-injection, alternating injection, and novel pure CO2 injection with dissolved surfactant; with field scale simulation, exhibit the considerable superiorities of CO2-soluble surfactant over conventional aqueous surfactant through SAG and co-injection with variable perforation interval or slug size; investigate the unique characteristics of the novel CO2 foam, including surfactant delivery media, optimal injection strategy, and some additional considerations; and examine whether previous conclusions in the literature for conventional surfactants were still valid for this novel foam with our practical postulations
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