Cut expenses to prepare, ship, and treat offshore rig waste

An operator working offshore Newfoundland had introduced cuttings reinjection waste management practices in a challenging environment that can complicate logistics and drive up costs. In keeping with regulatory requirements and company standards, all deck drainage, slop water, and waste fluid from the West Aquarius semisubmersible rig had to be treated offshore and meet transfer-to-shore standards, including an oil concentration level below 15 mg/L [0.0015%]. Shipping preparations, transportation to a third-party onshore treatment facility, and associated cleanup all contributed to significant operational costs.

Improve rig efficiency with modular ENVIROUNIT system

M-I SWACO recommended the ENVIROUNIT offshore water treatment system to process the West Aquarius rig’s deck drainage, which included rain, spillage, washwater, and contamination from hydrocarbons, drilling and completion fluids, and rig-cleaning surfactants. The rig-based modular ENVIROUNIT system treats and recycles drilling and completion wastes that previously had to be sent to shore for disposal. The system enables operators to meet mounting offshore discharge quality requirements, recycle more fluid, mitigate HSE risks, and reduce logistics costs.

Significantly reduce expenses and HSE risks

Approximately a month after its installation on the West Aquarius rig, the ENVIRONUNIT system discharged the first 95 m³ of processed deck drainage. Over the next four months, the operator reported cost savings of USD 1,191,408 compared with expenses for traditional ship-to-shore methods. The system reduced monthly slop treatment costs by an average of USD 250,000 and is expected to save USD 3.2 million over the first year of operation. With discharge costs reduced by 10% in the first year and by 5% in subsequent years, the operator expected to save nearly USD 15 million over the course of the contract.

Additionally, the unit has complied with all environmental regulations and greatly reduced HSE risks associated with managing deck drainage, resulting in reductions in offshore supply vessel tank cleaning, confined-space tank entries, the number of heavy vehicles transporting waste in cities on public highways in populated areas, and the use of biocides such as H₂S scavengers. Treated liquid is now discharged overboard after testing has confirmed that fluids comply with regulatory standards. Reusable drilling fluid components are recovered and recycled into the active drilling system, further reducing the cost of operations.

The operator realized additional significant reductions in contaminated solids for shipment, greatly reducing costs, vessel traffic, and associated HSE risks. The ENVIRONUNIT system mitigated high-risk logistics and fluid transfer practices, improved overall operational efficiency, and reduced dependence on cost- and time-intensive disposal methods.