Two-Stage De-Oiling Testing for Qualification with MEG Presence

摘要

Chevron Energy Technology Company performed a flow loop qualification under realistic conditions for a two-stage de-oiling unit in order to test the performance and robustness, especially for subsea developments. The objectives of this qualification were to investigate the effects of both high pressure and the presence of mono-ethylene glycol (MEG), under as realistic conditions as possible, on the system performance using crude oil and water. MEG is a gas hydrate inhibitor which will likely be injected in long subsea tie-backs. The tested compact produced water treatment system consisted of a two-stage de-oiling arrangement in which the first stage was a bulk de-oiler hydrocyclone, and the second stage was a polishing hydrocyclone. Each stage consisted of a pressure vessel which was filled with multiple hydrocyclone liners. For this qualification, Sulzer's MixedFlow De-Oiling Liquid-Liquid Hydrocyclone technology was used. Sulzer hydrocyclones utilize a design with multiple openings in the inlet as well as a swirl generation element, resulting in a stabilizing and coalescing effect on the oil-water flow. The system was tested at a high pressure test loop with crude and methane to provide the most realistic testing conditions. Tests were also performed with MEG in the feed. MEG is required for gas hydrate inhibition, and under some operating conditions MEG can influence de-oiling efficiency during produced water treatment. For this reason, test points with and without MEG present in the feed were included in the test matrix.