Streamlining Zinc Removal From Completion Fluid Flowback And Produced Water In Offshore Oil & Gas Production

Abstract

Abstract This paper and its presentation provides an overview of an innovative way to treat zinc-contaminated water that might, for example, result from the use of completion fluids with extremely dense zinc bromide—up to 19.2 pounds (8.7 kilograms) per gallon—in high-pressure wells. Traditional approaches to treating zinc from completion fluid flowback and produced water are cumbersome and costly, with potential for perpetual liabilities associated with onshore in-ground disposal. Discussed will be a simpler, highly effective system that can save as much as 25 percent or more in zinc treatment and disposal costs. The patented system combines two technologies—reverse osmosis (RO) membrane and ion exchange (IX) resin—to minimize zinc waste volumes. It works without chemicals and has a relatively low residence time. By selectively removing zinc, the remainder of the salts and most of the water can be discharged to the ocean. The zinc-removal system is available in two options: (1) RO with IX and (2) IX only. Both components arrive in a skid-based, offshore package. The entire system is fully compliant with API RP 14C safety standards and can operate as a standalone or integrated with pre-treatment systems that separate oil and other contaminants from completion fluid flowback or produced water. In a 2019 efficiency test with a large independent E&P operator in the Gulf of Mexico, the system treated 36,387 barrels of water using five pairs of IX resin columns that together averaged 5 barrels-per-minute flow rates, with four total backwash cycles. Because the TDS of the produced water was already high, RO was not needed as part of the treatment system. Ultimately, the operator was able to discharge 35,400 barrels of water overboard instead of being collected and sent ashore. Only 900 barrels of zinc water from the IX resin columns needed to be sent ashore for disposal, although that amount was reduced by 75 percent to just 225 barrels upon the system's second deployment a month later.