Innovation to Reduce Operation Downtime in Sulfate Removal Offshore Applications

Abstract

\n Sulfate removal in injection water is standard practice to prevent scaling and souring in subsea oil reservoirs. Nanofiltration membranes have been used to this purpose since 1987, when FilmTec™ SR90-400 elements were installed in an offshore platform in the North Sea. The most pressing concern in this type of systems is membrane fouling, with the associated reduction in effective plant operation time and shorten element lifespan caused by the standard Clean-in-Place (CIP) protocols. The object of this research has been to test the latest developments in biofouling-resistant sulfate removal membranes to achieve oil and gas (O&G) industry requirements. Improved chemistry and improved module engineering have enabled the production of new membrane elements that represent the next-generation in sulfate removal nanofiltration. Next-generation sulfate removal membranes have been trial-tested. In pilot testing, target performance was validated in terms of productivity, permeate quality and fouling resistance. The results of this testing indicate that improvements in membrane chemistry and module engineering have resulted in a 63% decrease in pressure drop and a much slower fouling trend over the total of 6 elements. This significant improvement should allow an important reduction in the number of cleanings, which the authors have estimated to be of 50%. Moreover, sulfate rejection values are in the range of 99.9% (below 1 ppm of sulfate in the permeate), providing great injection- quality water. Full-scale testing in a production site in the Atlantic Ocean was done to validate pilot testing results, showing a continued operation of 100 days without any need for a clean-in-place (CIP) procedure. The results obtained in the extensive testing carried out on these new antifouling elements, show that the improvements implemented in its design have the ability to improve the operation of Sulfate Removal Units (SRU). These improvements are the results of reducing maintenance costs and downtime on offshore platforms, resulting in increased operation and improved productivity.