Biodegradable Anti-Agglomerant Chemistry for Hydrate Plug Prevention in Various Production Conditions

Abstract

Performance of anti-agglomerants (AAs) depends on many factors, including salinity, water cut (WC), characteristics of the hydrocarbons, gas composition, reservoir conditions, production system conditions, and especially AA stability at the application conditions. Most AAs are surfactants, with one or multiple long hydrophobic tails and a charged hydrophilic head. This class of chemistry is often not easily degraded in the environment and can, therefore, be eliminated from consideration for application in environmentally sensitive regions. This paper presents the development of an AA that can be applied under a wide range of production conditions and is unique because of its ready biodegradability [>60% compared to other AAs, which either are not biodegradable (<20%) or can only achieve inherent biodegradability of 20 to 60%]. Rocking cell testing was conducted to determine the performance boundaries of the AA chemistry. Light, medium, and dark oils from various fields were used to evaluate the performance of the AA in aqueous phases ranging from condensed water (effectively, 0% salinity) to high salinity (~12%). Test results were categorized as "pass" for transportable hydrate slurries and "fail" if the systems plugged, and/or showed large hydrate crystals, and/or resulted in high slurry viscosity. Visual observations throughout the test and proximity sensor data provided qualitative and quantitative representations of the behavior of fluids in each cell. Water quality and emulsion tendency testing were conducted to verify that the AA would be suitable for offshore use and operable at topside. Biodegradation testing of the AA was conducted in seawater according to OECD 306 (1992). Systematic study demonstrated strong versatility for application of this AA to help prevent hydrate blockages in pipelines. Optimizing the head and tail length of the molecule was crucial for allowing it to treat a wide range of salinities, WCs, and oils with different API gravities. No sign of hydrate blockage was observed when applying the designed AA at minimum effective dosage (MED). The optimized product demonstrates overboard oil and water quality, thereby eliminating the need for an emulsion breaker and/or a water clarifier. The presented AA has a ready biodegradability of 61.8% [greater than 60% is categorized as readily biodegradable using OECD 306 (1992) methodology] and has been successfully implemented to treat hydrate plugging in the Gulf of Mexico (GOM).