Control by Design: Mitigating Foams in Compact Separators

Compact and subsea separation methods have become increasingly commonplace in many offshore oil and gas operations. Compact equipment have been instrumental in debottlenecking existing operations, as well as enabling production in some cases. While the benefits are plenty, the primary challenges with designing such compact, and especially, subsea installations have been their reliability and availability under operating conditions where intervention is difficult, to say nothing of the production losses, or the risks arising from a severe malfunction. In recent times, there have been early production losses due to problematic multiphase flows resulting in excessive liquid carry over and gas carry under from subsea separation equipment, likely due to unresolved foam. The state-of-the-art for handling such foam issues has been the use of defoamers. While this may work in some cases, often times the dosage is either higher or lower than the actual requirement – this happens primarily because of a lack of a rapid monitoring and response to foam being created in the separator or upstream of it. This work is rooted in the idea of primary foam mitigation by effective design and minimization of chemical treatment, and focuses on a novel design paradigm for separators to mitigate the risk due to foaming. Results show that in some cases any unexpected event causing the foam stability to double may increase the chance of liquid carry-over or gas carry-under by a factor of three, underlining the need for an effective control by design strategy.