Chemical-foam Design as a Novel Approach Towards Immiscible Foam Flooding for Enhanced Oil Recovery

Abstract

Summary Foam flooding as an enhanced oil recovery (EOR) method can greatly improve Water-Alternating-Gas (WAG) injection and Cyclic CO2 injection in the secondary phase of oil production. However, foam flooding suffers from a lack of high efficiency in terms of oil recovery compared with chemical EOR methods. Despite of possibility of generating strong foam in the presence of oil, incremental oil recovery by the foam flooding is limited. Additionally, a noticeable portions of oil recovery by foam flooding are as mixture with a surfactant solutions, which involves the oil separation from emulsion which won’t be economically favorable. To tackle these issues, this paper presents experimental study of a novel alkali-surfactan-t foam(ASF) flooding process as a chemical-foam design to improve immiscible foam flooding. The ASF enhanced oil recovery (EOR) process involved the use of alkali-surfactant solution as a slug and foam as the drive to mobilize and displace the remaining oil after water flooding process. In this study, a blend of two type of anionic surfactant formulations was formulated for slug and drive: IOS, which exhibits low interfacial tension (IFT), AOS which creates strong foam. Prior to the oil recovery experiments, foam mobility reduction behavior at the transient and steady state condition in the absence of oleic phase was investigated. During this, experiments performed using the Bentheimer sandstone cores, pressure-drop measurement aimed to determine foam solutions’ ability to reduce total mobility. X-ray CT images were taken during foam generation to find out the stability of advancing front of foam propagation and to map the gas saturation. Then, proposed ASF strategy for enhanced oil recovery was tested through the co-injection of immiscible nitrogen gas and slug/drive surfactant solutions with three different formulation properties in terms of IFT reduction and foaming strength capability. The performance of this ASF slug/drive chemical formulation was evaluated by a core-flood test on Bentheimer sandstone rock with the aid of X-ray computed tomography. The discovered optimal formulation contains a foaming agent surfactant, a low IFT surfactant, and a co-solvent, which has high foam stability and low IFT (1.6 *10–2mN/m). This co-injection gave higher oil recovery and much less MRF than the same process with only using a foaming agent. Oil displacement experiment revealed that co-injection of gas with a blend of surfactants containing co-solvent can recover a significant amount of oil recovery (33% OOIP) over waterflood.