Abstract

Bitumen recovered from the Athabasca oil sands during steamflood operations is mostly in the form of an oil-in-water emulsion. Such emulsions are typical of the production from Texaco's steamflood pilot at Ft. McMurray. Alberta, Canada. Texaco Canada Resources has operated three separate experimental patterns at this pilot since 1971. Operational and laboratory evidence obtained during the course of this pilot supports the theory that emulsification of the bitumen occurs within the reservoir although further emulsification may occur at wellbore entry points and production control orifices. The viscosities of oil-in-water emulsions are known to be much lower than the oil itself, and therefore in-situ emulsification should be considered beneficial to the recovery of heavy oils and bitumen. In an effort to understand the rheological properties of these emulsions, Texaco sponsored a proprietary research project at the University of Alberta to study the effect of chemical additives on the stability of oil-in-water emulsion flow through porous media.

The primary objective of the work presented in this paper was to investigate the effect of caustic and petroleum suffocate on the stability and transportation of oil-in-water emulsions through a clean unconsolidated sandpack. The oil component of the emulsions studied comprised a synthetic crude oil containing about 40% unsaturated hydrocarbons. The function of the chemical additives was to promote the emulsification or dispersion of the oil into an aqueous phase. Results involving the flow of emulsions of oil-in-water containing 1% to 10% synthetic crude are reported. An investigation into the effect of salt on the stability of these emulsions was also undertaken and interfacial tension measurements, postflood core analysis and particle, size analyses are reported. The flow behaviour of the emulsion as it passed through the porous media and the significance of oil/aqueous phase interfacial tensions on stability and flow are discussed.

Introduction

Since bitumen recovered from the Athabasca oil sands during steamflood operations is usually in the form of a bitumen-in-water (O/W) emulsion, it 1S important to understand the movement of these emulsions through the reservoir. A review of the literature revealed that relatively little experimental data has been collected on the flow of emulsions through a porous medium. Researchers such as Marsden, Devereux and McAuliffe conducted studies which led to early formulations of mechanisms for the flow of oil-in-water emulsions through purges solids. ' Further work carried out by Alvarado, Hallam, and most recently by Soo and Radke, produced results which both confirmed and disputed some of the earlier findings. It is evident that further work in this area is warranted if a thorough understanding of emulsion flow phenomena is to be obtained.

The main objective of the work presented here was to investigate the effect of various chemical additives on the stability and transportation of O/W emulsions through a clean unconsolidated sandpack. Experiments were designed to determine whether the emulsions would remain stable when transported through a porous medium.

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