Extension of field life and economical development of marginal fields are both critical to the oil and gas industry. Maintaining the integrity of aging assets is a priority as well because it extends the life of costly infrastructure through retrofits and tie-back of marginal fields. The necessity to extend asset life and make marginal discoveries economically viable is enforced by the various cycles that affect the industry, requiring a detailed control on capital expenditure and the production cost of small discoveries.

Tying-back marginal fields to existing infrastructure reflects the industry’s desire to move process equipment subsea and reduce footprints on existing infrastructure. Such subsea equipment can reduce development costs while enhancing reservoir productivity.

Water injection is a key enabler for the optimal recovery of hydrocarbons. Typically, water injection requires a topside processing plant consisting of several treatment steps to tailor water qualities to each reservoir’s specifications.

National Oilwell Varco’s (NOV’s) Seabox subsea water treatment system moves water treatment subsea, where it disinfects and removes larger particles. Disconnecting water treatment from topside infrastructure enables longer tieback solutions—thereby ensuring optimal recovery for marginal fields.

The Seabox subsea water treatment module provides a flexible approach to integrate water treatment to your field. The module can be placed at the foot of your platform or close to the injector, feeding clean water for injection or further topside processing.

The system, which has a standard treatment capacity of 40,000 bbl per day, disinfects the seawater with in-situ electrolysis processes that generate sodium hypochlorite and hydroxyl radicals. In recent tests the Seabox module removed 99% of particles greater than eight to ten microns. Of these, a significant share were even less—down to two microns.

Particle removal relies on sedimentation— with no filters needed. When placed at the seabed, the Seabox module leverages its location to allow the design to be sized for an extended period of residence, enabling the sodium hypochlorite to react with the seawater, which provides thorough disinfection that produces superior clean water. Since there aren’t any moving parts, the environmental footprint is significantly reduced; the need for chemicals is eliminated and power consumption remains below 10 KW.

The Seabox module has been performing in operational conditions in Ekofisk, Norway since October 2018. Prior to that, sedimentation and disinfection capabilities have been verified through three months of operational testing outside of Stavanger, Norway. The module can be combined with additional ultrafiltration and membrane systems to further tailor water qualities to fit exact reservoir specifications.