Experimental Investigation of a Polymer-Enhanced N2 Foam Performance for Enhanced Oil Recovery

The Bohai oilfield is a typical commonheavy oil reservoir withhigh water cut after long-term water injection development. Consideringthe characteristics of selective plugging, polymer-enhanced foam (AOS-DYG)flooding was adopted in this study as a subsequent enhanced oil recovery(EOR) technology in the Bohai Sea. A polymer can promote foam stabilityby reducing the foam drainage rate and enhancing interfacial adsorptionbehavior. As a result of its low cost and abundant sources, nitrogenis selected as the air source of foam in this paper. The interactionbetween the polymer DYG and the surfactant AOS was clarified fromthe aspects of surface adsorption properties, surface dilated rheologicalproperties, bulk phase rheological properties, and micromorphology.That is, the addition of polymer can increase the thickening abilityof the foam-based liquid phase, the thickness of the liquid film,and the strength of the gas-liquid interface adsorption layer,all of which dramatically improve the stability of the foam. The coredisplacement test results further confirmed that the AOS-DYGfoam displaced an excellent mobility control ability in porous media.When the foam mass (gas-liquid ratio) was 70% and the injectionflow rate was 1 mL/min, the resistance factor and residual resistancefactor at 2264.7 mD reached 246.11 and 127.33, respectively. Withan increased core permeability, the oil displacement performance ofthe AOS-DYG foam increased. The enhanced oil recovery (EOR)of the 0.4 PV AOS-DYG foam in the 2547.8 mD core reached 32.19%,demonstrating an outstanding oil displacement capacity. The findingsof the investigation supported the potential application of the AOS-DYGfoam in EOR.