Abstract

Eco-friendly water deoiling systems for effective water treatment presents a significant operational and environmental challenge during exploration and development well testing and clean-up operations in offshore environments.

As an alternative to traditional storage, transport, and disposal onshore, some offshore operations have attempted to use mobile water treatment systems to reduce the oil-in-water content from the produced water to an acceptable level, before safely discharging overboard in accordance with the local regulatory permitted environmental limits. When this can be routinely and effectively performed, offshore water treatment units may provide an efficient and cost effective alternative to conventional approaches of onshore treatment and disposal of aqueous effluents and waste streams.

This paper outlines the operational envelopes and limitations of current commercially available water deoiling systems, and introduces a relatively recently developed mobile light water treatment unit. This new generation light water treatment unit consists of a horizontal vessel containing five coalescing beds evenly distributed along the vessel length and inlet centrifuge for solids removal. The vessel combines both coalescing and gravity separation techniques that is capable of reducing oil-in-water (OIW) concentration to less than 20 ppm. The primary coalescing material is a reusable petroleum absorbent polymer that can be regenerated through centrifugation onshore. Therefore, unlike more traditional water filtration and deoiling systems, it generates no additional waste or by-products.

The field applications highlighted in this paper demonstrate the results and lessons learned from successful deployments of this new generation light water treatment unit in firstly offshore well test operations and subsequently the inspection and dewatering of subsea pipelines in environmentally sensitive areas.

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