In a contract worth £500,000, CETCO Oilfield Services has provided a permanent water treatment package to the Apache and Santos Stag platform in North West Australia.

CETCO Oilfield Services, specialists in cost effective environmental technology, shipped a 48in diameter CrudeSep Induced Gas Flotation (IGF) unit to the Stag platform as part of a planned produced water treatment system upgrade.

CETCO’s CrudeSep technology is designed for the high efficiency removal of oil, gas and solids either upstream or downstream of a three phase separator. Within a CrudeSep vessel, gravity oil separation is enhanced by induced gas flotation and swirling flow, where gas bubbles are injected midway up the vessel using eductors. Produced water is then withdrawn from the CrudeSep in the lower half of the unit and used to drive the eductors.

During trials of the 48in diameter CrudeSep on the Stag platform, the unit achieved an oil recovery rate of up to 96% when utilised in conjunction with the recycle pump and an inlet injection of chemical RBW24362. At this level of performance the inlet oil in water (OIW) levels ranged between 200ppm and 9,000ppm with the outlets being as low as 10ppm.

The average efficiency of the skid unit was over 75% throughout the optimisation trails and once the units recycle pump was utilised online, the average efficiency increased to 89% and at times was observed as being as high as 96%.

CETCO’s patented CrudeSep technology is an instant and reliable treatment for managing produced water. Traditional produced water treatments tend to be designed for a certain flow rate, pressure, solids loading and oil loading.

With predefined parameters, most treatment packages can adequately manage produced waters, however typically these parameters do not remain constant during actual operations.

This was evident in a number of areas during the commissioning of the CrudeSep unit to the Stag platform. Rapid, fluctuating flowrates initially affected performance levels and samples taken from the inlet of the CrudeSep unit indicated sand particles, something which can lead to a potential build up of solids, resulting in oil wet solids in the aqueous stream. Consequently, CETCO’s CrudeSep system is uniquely tailored to manage unconventional discharge problems and operate effectively regardless of variable conditions.

“When we began trialling the CrudeSep unit, inlet OIW levels were significantly higher than anticipated,” explained Matthew Bradnock, CETCO’s sales and operations representative in Perth, Western Australia. “Nonetheless the CrudeSep technology still performed at a high oil recovery rate.”

“We have tailored a package to meet the needs of Apache and we are confident that our water treatment system can ensure continued efficiency rates akin to those demonstrated.

Continuing, Matthew said, “This is a significant contract for us and we are delighted to have been involved in upgrading the Stag platform’s existing produced water system. I would like to thank all of the crew members on the Stag for their help, assistance and safe working practice throughout the trial period and mobilisation of the treatment package.”

In addition to the supply of the unit, CETCO has supplied specialist personnel to operate the unit and provide training to the Apache offshore workforce.

CETCO specialises in treating completion fluid, acid flowbacks, produced water and the removal of hydrocarbons from wastewater streams so that fluids can be discharged directly into the environment.