Subsea Mechanical Dispersion (SSMD) a Possible New Option for the Oil Spill Response Toolbox?

The size distribution of oil droplets formed in subsea oil and gas blowouts is known to have a strong impact on their subsequent fate in the environment. Small droplets have low rising velocities, are more influenced by oceanographic turbulence and have larger potential for natural biodegradation. Subsea Dispersant Injection (SSDI) is an established method for achieving this goal, lowering the interfacial tension between the oil and water and significantly reducing oil droplet size. However, despite its many advantages, the use of SSDI could be limited both by logistical constraints and legislative restrictions. Adding to the toolkit a method to achieve subsea dispersion, without the use of chemicals, would therefore enhance oil spill response capability. This option is called Subsea Mechanical Dispersion (SSMD). An extensive feasibility study on SSMD has been performed and the main findings are reported in this paper. The work was initiated by BP in 2015 and later followed up by a consortium of Equinor, Total Norge, Aker BP and Lundin. The first phase explored multiple principles of generating subsea dispersions (ultrasonic, mechanical shear forces and water jetting) through both laboratory experiments and modelling. These studies clearly indicate that SSMD has an operational potential to significantly reduce oil droplet sizes from a subsea release and influence the fate and behaviour of the released oil volume. The recent work reported in this paper on operationalisation, upscaling and large-scale testing of subsea water jetting. This work is performed by SINTEF in close cooperation with Exponent (computational fluid dynamics and shear stress modelling) and Oceaneering (operationalisation and full-scale prototyping).