Abstract

A side effect of EOR polymer flooding on topsides process chain is the generation of stable thin emulsion in viscous water phase. Both viscosity and severe emulsion impede the efficiency of water treatment technologies. The viscosity of the back produced polymer increases the time of clarification of oily water phase. The target of the water treatment specialist would be to collapse the viscosity of the produced water.

The main concern is to decrease the viscosity of the produced water containing polymer back produced, acting on the degradation of the polymer without generating more severe oily emulsion. Shearing, a well known mode of degradation has been compared to other techniques such as chemical oxidation (bleach) and sonication. All the tests were performed with a high molecular weight polyacrylamide commonly used in EOR; at bench lab scale on synthetic viscosified produced water and on back produced water from field with cEOR flooding. Degradation efficiency was evaluated through viscosity measurements and polymer molecular weight analyses.

This paper presents the results of the different investigations carried out to drop the viscosity of the produced water to an acceptable value for water treatment. Chemical oxidation using bleach has proved its efficiency on synthetic produced water. Different shearing conditions and different powers of sonication have also highlighted actions on the polymer and on the viscosity of the water phase.

Even if all the tested degradations lead to a significant viscosity drop of the synthetic viscosified water, the improvements on water treatment were not equivalent. Analytical measurements of the molecular weight of the degraded polymer allowed initiating a scale of degradation efficiency.

The efficiency, feasibility, difficulty, beneficial impact on water treatment and level of readiness of the technology have been estimated. An assessment of the different techniques for the polymer degradation in water treatment is presented at the end of this paper.

The feasibility to decrease the viscosity of the back produced water would allow to simplify the water treatment process chain dedicated to polymer flooding case. Works continues on integrated water treatment process, including pre-degradation of the polymer back produced.

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