With an increase in challenging offshore environments and additional well tie-ins, the need for more effective offshore separation technologies is greater than ever, especially for produced water management. The amount of produced water, contaminants, and concentrations can differ significantly over the life of a field, so a more efficient and suitable system is required to achieve higher water cleanliness.
Subsea produced water treatment technology is maturing, and large, horizontal subsea water tanks are under development as a last separation stage to achieve high water cleanliness and production stability. Our produced water treatment tank (PWTT) system is designed to achieve a large buffer volume to smooth out variations in the outlet water quality (from upstream separator) and to achieve the required water quality of dispersed oil-in-water at 15 ppm or lower. This process is not being achieved with today’s technology, as the treated water is directly discharged to sea or re-injected into the reservoir.
Our system consists of two horizontal PWTTs, a sand management system, power and control system (including pressure and buoyancy protection mechanisms), fluid transfer system, and a cluster frame. The PWTT system is designed with the appropriate residence time for settling of solid particles and flotation of oil droplets. The system is gravity based and does not require any chemicals, making it environmentally friendly. The technology also aims to eliminate surface facilities associated with water treatment, reducing overall investment and operational costs.
The PWTT functions at a low operating pressure (above ambient hydrostatic pressure) with a gas phase to improve separation performance. This allows it to be placed anywhere on the seabed and at any water depth, depending on operator needs during the development and expansion of the field. Furthermore, the system is designed with oil-reject and gas-reject lines as well as a sand management system connected to an upstream sand accumulator, making the PWTT even more efficient and reliable.
Our PWTT is the ideal solution for additional well tie-ins, deepwater processing, and long tie-backs. As an economical and viable alternative to floating production storage and offloading vessels, the PWTT can be used in conjunction with our other water treatment technologies, including the Seabox™ system and our subsea storage unit for oil and condensates, helping to successfully move your processing infrastructure to the seabed.