The 135 D platform is located in the Campos Basin off the coast of Brazil. The platform functions as a central processing facility, receiving degassed liquids for treatment from four remote production platforms. Dry oil is sent via pipeline to Cabiunas, while water with <20 mg/L total oil and grease (TOG) is discharged overboard. Upon startup, the ability of the systems on 135 D to clean produced water to the required TOG of <20 mg/L was limited. This paper describes the means by which the fundamental causes of the water treatment performance problems were identified and resolved. Modifications to the original process design are discussed, and the impact of those modifications on the quality of discharged produced water is presented. The root causes that limited water treatment performance on 135 D were identified as a combination of very high variations in arriving fluid flow rates, unexpected variations in solids concentration, process recycle streams, unexpectedly small oil droplets, and sludge generated by the mixing of excess chemicals with inlet fluids. On-platform modifications to existing process vessels and to the process itself were required to successfully treat produced water whose character varied significantly from design specifications. Since completing modifications, the platform has routinely produced water with <20 mg/L TOG at or above plant design capacity.
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