A systematic approach to alkaline-surfactant-foam flooding of heavy oil: microfluidic assessment with a novel phase-behavior viscosity map

Eric Vavra,Maura Puerto,Sibani L Biswal,George J Hirasaki

doi:10.1038/s41598-020-69511-z

Abstract

The apparent viscosity of viscous heavy oil emulsions in water can be less than that of the bulk oil. Microfluidic flooding experiments were conducted to evaluate how alkali-surfactant-foam enhanced oil recovery (ASF EOR) of heavy oil is affected by emulsion formation. A novel phase-behavior viscosity map—a plot of added salinity vs. soap fraction combining phase behavior and bulk apparent viscosity information—is proposed as a rapid and convenient method for identifying suitable injection compositions. The characteristic soap fraction, {X}_{soap}^{Sor}, is shown to be an effective benchmark for relating information from the phase-viscosity map to expected ASF flood test performance in micromodels. Characteristically more hydrophilic cases were found to be favorable for recovering oil, despite greater interfacial tensions, due to wettability alteration towards water-wet conditions and the formation of low apparent-viscosity oil-in-water (O/W) macroemulsions. Wettability alteration and bubble-oil pinch-off were identified as contributing mechanisms to the formation of these macroemulsions. Conversely, characteristically less hydrophilic cases were accompanied by a large increase in apparent viscosity due to the formation of water-in-oil (W/O) macroemulsions.

Highlights

The apparent viscosity of viscous heavy oil emulsions in water can be less than that of the bulk oil
internal olefin sulfonate 15–18 (IOS) is a commonly tested surfactant in chemical enhanced oil recovery (EOR) studies and lauryl betaine (LB) has been demonstrated to be a foam booster in the presence of oil[42,43,44,45]
A novel phase-behavior viscosity map was proposed as an experimental method to aid in the rapid selection of optimal injection conditions for displacing heavy oil as a low-viscosity oil-in-water (O/W) emulsion

Summary

Introduction

The apparent viscosity of viscous heavy oil emulsions in water can be less than that of the bulk oil. More hydrophilic cases were found to be favorable for recovering oil, despite greater interfacial tensions, due to wettability alteration towards water-wet conditions and the formation of low apparent-viscosity oil-in-water (O/W) macroemulsions. Recent works have predicted an increase in the role of heavy oil in the global energy landscape[1,2,3,4,5] This oil, with viscosity ~ 10–106 cP, is typically produced by enhanced oil recovery (EOR) methods[2]. In deep formations at high pressures, higher temperatures are necessary to generate steam[7] Those cases could require prohibitively large energy consumption or CO2 generation. These drawbacks motivate investigation of alternative EOR processes for recovering heavy oil. These phenomena, the formation of macroemulsions, a process that depends on both wettability and IFT, stands out as a promising method for mobility control

Methods

Results

Conclusion