Abstract

Experimental results on heavy oil-in-water (o/w) emulsification using commercially available emulsifier in the presence of produced-sand particles are presented In this paper. Several emulsifiers were tested for emulsion type quality and sand-retention capability. The measured viscosities of the olw emulsions are presented. The effects of polymer addition on the viscosity and sand-carrying capability of the emulsions are also presented.

The results of the beaker tests indicate that almost all the aqueous chemical solutions water-wet the beaker wall and improve heavy-oil dynamics. However, most of the chemicals also water-wet the sand particles and cause sand dropout. Some chemicals form a water film along the beaker wall and also retain sand after emulsifiers. The addition of polymer material also resulted in very good sand-retention capability.

Introduction

The high viscosity of heavy oils produced under primary production and of oil-continuous water-in-oil (w/o) emulsions produced under enhanced oil recovery techniques, causes several operational problems, which include low pump volumetric efficiency, slow rod drop rate, rod parting, and high flow-line pressure drop.

Several methods have been proposed in the literature to overcome these problems. These methods include the application of bottomhole heaters and light oil diluents(1), water injection(2), and downhole emulsfication(3,4,5,6)(DHE). Among these methods, DHE proves to be the most cost-effective operational technique to produce heavy oil

Heavy oil usually carries a significant amount of formation fines when produced under primary operations. Efforts have been made to prevent sand migration into the wellbore by chemicals, high temperatures(7) or installation of mechanical filters(8). Although these methods proved to be successful in controlling sands in heavy-oil wells, they also caused several operational problems (i.e., plugging of slotted liners, screens, and near-wellbore formation).

On the other hand, sand production from heavy-oil formation is beneficial because it improves near-wellbore permeability. It would be Ideal to have a process which would enhance heavy-oil production, along with the entrained sand particles, and cause no sand-related workover problems. Although the DHE process enhances viscous heavy-oil production by reducing viscosity, the application of this process causes increased sand-related workover frequency. The increased workover frequency has two effects:

  • to increase operating cost, and

  • to increase the chances of near-wellbore formation damage due to asphalteno precipitation (when light hydrocarbon mixtures are used as workover fluids).

To reduce the sand-related workover frequency, a better understanding of the fundamentals of the emulsification process in the presence of sand was necessary. Extensive studies have been published on the formation, stability, and quality of emulsions in general(9,10,11). The formation, quality and rheological properties of heavy-oil emulsions have also been studied extensively(12,13,14,15). However, information on heavy-oil emulsification in the presence of sand particles was not available in the literature.

In this paper, the results of a research study on heavy-oil emulsification in the presence of sand particles are summarized. The field application of these results has potential for sand control during downhole emulsification.

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