Elimination of Sheen in the Ocean Generated by Overboard Water from Offshore Crude Oil Production Facilities

Abstract

Abstract The objective for the technical proposal, related to the Offshore water clarification Bottle test, is to propose a list of clarifiers alternatives for organic solids and oil removal that cause eventual discoloration (Sheen), observed at several offshore production facilities at sea water. Due the impact of overboard produced water quality, one of the causes is the type of clarifier implemented (di-thiocarbamate molecule - DTC), which will be replaced with a non-DTC molecule and improve some overboard water issues. After this new chemical application, crude oil Producers will re-evaluate the overboard produced water parameters, to understand if there is the need to improve the water quality. The test must follow several requirements as a visual water aspect (ocean surface - Sheen) improvement. New technic of investigation and a successful field trial. White and milky aspect can be caused by insoluble water clarifier in the produced water. The sheen aspect in the ocean can be evaluated with actual lab tests, using the Turbidity scan equipment and incumbent product, that is showing poor transmission and poor back scattering. Solids and iron detected by Flow Camera and XRF instruments are proving the accumulation of solids and iron in the top of the ocean, causing a long sheen length in the ocean. According to the procedure stablished for field trial, after all chemical studies, bottle test, organic solids investigation and analysis of Sea Water surface visual aspect during the trial, to validate the Clarifier and Sheen removal treatment, observing if the discoloration issue would be solved after the injection in the system. Also, the following parameters were measured during the trial: Oil in Water (OIW, ppm), Turbidity (NTU – Nephelometric Turbidity Unit), Iron content (Iron II, Iron III and Total Iron) and Total Suspended Solids - TSS (onshore). A combination of coagulant and flocculant products pre-selected with a severe and deep produced water and Floating Production Storage and Offloading - FPSO production studies, demonstrated an excellent performance during the field trial, and any discoloration in the ocean surface was observed on the overboard point, as we could observe before the field trial. The analysis quickly reached the expected values established in the procedure, and this was a great quality demonstrated by the efficiency of the product in the field application.