Abstract

In the Kutei, Indonesia oil and gas producing basin, a serious flow assurance problem has occurred in the form of an oil-water emulsion. This emulsion, formed via the reaction of carboxylic acids in oil with sodium-chloride-bicarbonate-acetate produced water, is difficult to break. At the West Seno deepwater field, the floating production unit (FPU), utilizes heat and an acidic demulsifier to break the emulsion into salable oil and water suitable for overboard discharge. Over the past couple of years, a few wells have begun to produce an emulsion that is not easily broken by the FPU heat/acid demulsifier process. Characterization studies of the new emulsion show that it is very different chemically from the common sodium soap emulsions produced at West Seno field since production inception in 2003. The former contains primarily sodium alkyl benzoates, while the latter consists primarily of sodium n-alkanoates ranging from C10 – C36. Oil produced from the wells that produce the new "difficult" emulsion is waxier than normal. The combination of waxes and the alkyl benzoic acids is apparently responsible for the formation of the "difficult-to-treat" emulsion.

Laboratory screening tests of new sodium soap emulsion inhibitors have shown that heat and several non-acid inhibitors break the emulsions more efficiently than the incumbent acid demulsifier. One new inhibitor was especially efficient and more cost effective than all other inhibitors included in the study. Not only is this new inhibitor more effective at a lower dosage, but its bulk price is also less. This inhibitor was injected into two West Seno wells that produce the "difficult" emulsion in a short field trial. Coupled with reservoir heat, the inhibitor successfully broke the emulsion at a reasonable dosage. The chemical appears to inhibit sodium alkyl benzoates and sodium n-alkanoates via a complexation mechanism. We are now preparing for commercial deployment of the new inhibitor in West Seno wells. We believe that the new inhibitor will eliminate or reduce the need to treat fluids on the FPU with the incumbent acidic demulsifier, which should reduce corrosion and by-product scaling caused by the incumbent.

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