In an age of heightened environmental awareness and regulatory requirements, offshore technology is charged with meeting new stringent operational challenges. It is clear the challenges and mandates for cost-effective and sustainable water management will only increase over time. To accomplish the important goal of robust and cost-effective produced water management, engineers at MyCelx Technologies have worked with industry leaders to implement MyCelx Clean Water Systems to meet economic and environmentally responsible objectives.

Contending with WSOs

Water-soluble organics (WSOs) are an increasing challenge since they contribute to the total oil content of produced water. Traditional water treatment technology is stretching to meet the challenges of produced water treatment faced in deepwater production where the WSOs and strong oil-in-water emulsions are present. MyCelx Clean Water Systems, on the other hand, are capable of reliably treating free and emulsified oils and WSOs from water to between zero and 10 parts per million (ppm).

The technology operates on the principle of chemical cohesion, which is a clean technology break from other existing produced water treatment technologies that are based predominantly on mechanical separation, adsorbent, or absorbent technology. Chemical cohesion enables the system to remove free, emulsified, and dissolved hydrocarbons in water.

The MyCelx Oil Removal System maintains high water discharge quality under variable loading conditions due to upset operation of the pretreatment systems, which results from unpredictable day-to-day loading of the produced water from production wells and the presence of WSOs and emulsified oils. (Data courtesy of MyCelx Technologies)

This technology was first implemented in Anadarko Petroleum Corp.’s saltwater management facilities in Utah. Due to the presence of iron sulfides, WSOs, and emulsified oil in the produced water, various technologies like CPI separators, float cells, nut shell filters, organo clay, carbon, and chemical cohesion technology were rigorously evaluated by MWH Global, the engineering, procurement, and construction contractor at the production sites. After months of intense field evaluation , an optimum produced water treatment system was designed for full-scale implementation to consistently meet the 10 ppm surface discharge requirement at no visible oil sheen. During the pilot evaluations, the chemical cohesion system consistently treated and discharged water to less than 10 ppm total oil content including WSOs at variable influent oil loadings and upstream treatment process upset conditions.

The produced water treatment facilities at the site came online in late 2007 with a combined water processing capacity of 45,000 b/d. To date, the systems have treated more than 10 MMbbl of water with an average quality of less than zero to 5 ppm oil in water.

Technology adoptions

A number of onshore operators have adopted these systems at 10,000 to 40,000 b/d capacities as a fail-safe unit post existing oil recovery and treatment systems prior to discharge into sensitive environments. Successful onshore operations are being considered and implemented offshore for produced water treatment prior to overboard discharge.

The system has been optimized for offshore operations and has proven capable of removing oils and WSOs to consistently achieve zero to 10 ppm overboard discharge levels. It also offers flexibility as well as robust operational and footprint options not found with other produced water treatment systems.

The chemical cohesion system contends well with upset conditions, which are prevalent in offshore production due to engagement of new wells, presence of oil in water emulsions, suspended solids, WSOs, flow variations, and inline chemical dosage equipment malfunction. The technology can reliably reduce the total oil content in overboard discharge water to less than 10 ppm, preventing sheen. This gives offshore operators flexibility to troubleshoot the process upset conditions while sustaining the necessary quality level for overboard discharge water at all times. The system also has proven capable of handling varying and erratic levels of oil and WSO loading, providing discharge water that exceeds current regulations.

When new production wells are engaged and when they mature, the water production rate and quality of oil and hydrocarbon contamination in produced water can vary drastically. New wells can bring more flow fluctuations and WSOs/emulsified oils in the produced water that can limit the ability to process and discharge water overboard through existing produced water secondary treatment equipments. The chemical cohesion system can be engaged at full or partial flow to discharge quality water overboard without compromising production.

The version of the MyCelx Clean Water System on this worksite can process 10,000 b/d.

The systems are available as complete produced water systems that incorporate secondary and tertiary treatment capable of handling high oil, WSOs, and solids loading. A simple retrofit also is available. It can boost existing treatment train performance post float cells and remove oils and WSOs to 10 ppm – well below the 29 ppm requirement.

The MyCelx systems have a low turn-down ratio of 0.05, which means at 50,000 b/d the system performs the same as it would operating at 1,000 or 2,500 b/d. Traditional equipment and chemical dosage systems cannot automatically readjust to handle such a low turndown ratio.

The systems activate only in the presence of hydrocarbons, retaining no water in the process. This means a system on standby can be engaged when necessary without compromising oil and WSO removal capacity or effectiveness.

Moving from onshore to deepwater brings challenges. With the ongoing operator initiatives in deep water, operational challenges have come to light, and as a result, operators have been open to considering new complementary technology and equipment. Integrating existing proven technology with new technology will provide the best solution for sustainable produced water management.

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