Production at Total’s Ofon offshore oil rig, situated 60 kilometers south of Port Harcourt, Nigeria, recently tripled its daily output as part of its Phase 2 project.

In line with this expansion, Veolia Water Technologies in South Africa designed, fabricated and commissioned two new packaged water treatment plants, which will supplement the existing fresh water supply for cooking, cleaning and the HVAC system on the living quarter platform.

Veolia was responsible for supplying two package plants: one for desalination and the other for potable water.

To achieve this, the company built four skids. The first comprised a reverse osmosis unit with membrane pressure vessels, a Clean in Place (CIP) unit and the PLC to control the four skids.

The second skid was the dosing skid which provides the chemicals to both packages, the third skid contained two carbon filters and the fourth skid included ultra violet irradiation equipment and two pressure-sustaining vessels.

Relying on past experience

The process starts off with seawater desalination using reverse osmosis technology. The desalinated water is then transferred to an intermediate tank where it is chlorinated as part of the short term storage requirements.

The chlorinated water is then de-chlorinated through an activated carbon filter-set and thereafter some of the water is further disinfected through an ultra violet irradiation process.

This eradicates any bacteria and other living organisms. This process enabled the dual-stream requirements necessary for the functionality of both the desalination and potable water plants.

“We selected and designed all equipment to oil and gas specifications from Total, which included the relevant ATEX specifications, where necessary.” says Andre Loots, Project Engineer, Veolia Water Technologies South Africa.

Veolia relied on its expertise within the oil and gas industry to develop these highly technical designs. “We also had to ensure that the plants would integrate well with other packages on the oil rig.” comments Loots.

The company conducted its Site Acceptance Testing on the skids on the Mediterranean coast of France, which has significantly higher salinity levels than in the Atlantic Ocean where the rig is located.

“Our skids performed to specification even with this high salinity sea water and reaffirmed their performance capabilities for Total,” concludes Loots.