During completion and workover operations, water-based, oil-based and acid-based fluids are injected into the well, entering formation pores and reaching oil reserves. Depending on the flow intensity and ambient conditions, these fluids may interact with oil to form viscous emulsions, causing several problems in the reservoir and ultimately a decline in oil production. Non-emulsifiers, when added to brines and acid solutions, are supposed to act as a barrier on the interface between the oil and the fluid, preventing emulsion formation and helping to maintain fluid’s properties and preserving the oil in the reservoir. Lately, Brazilian fields have faced challenges that resulted into the use of different fluids and brines and also different types of oil to be dealt with. Thus, the purpose of this work was to adapt some of techniques of emulsion breakage to develop novel non-emulsifiers formulations that cope with current technical and environmental requirements regarding emulsion prevention for oil exploration in Brazil. A series of studies has been conducted in order to better understand the effect of different parameters on the emulsion prevention of brines during completion operations. A Design of Experiments approach has been prepared in order to test different formulations (varying solvent and co-surfactant natures and content) in different scenarios: brines with different salts and oils with different °API. Once evaluated through adapted bottle tests, aqueous toxicity of most promising formulations has been evaluated. It has been found that solvent and surfactant types and concentrations have great effect on emulsion prevention. All those parameters were taken into account and enabled the design of an optimized formulation for the application. Further, another Design of Experiments approach has been prepared in order to understand how different scenarios impact on emulsion prevention: the novel formulation was tested against brines with different salts and oils with different °API. The effect of parameters such as oil density, BSW, brine pH, brine type and agitation could be assessed and a mechanism of action for the high performance non-emulsifier could be investigated.

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