Improving subsea emergency response

Seanic Ocean Systems discusses the creation of a new subsea dispersant delivery system.

Overboard chute. Photos from Seanic.

The offshore oil and gas industry is constantly looking for ways to enhance its emergency response capabilities, through the development of new and innovative solutions. BP’s GWO-Subsea Wells (SSW) team, responsible for the firm’s containment response system (CRS) has developed a new subsea dispersant delivery system (DDS).

The SSW team developed a basis of design for the topsides and subsea equipment that would allow for the system to be quickly and easily altered to operate in a wide range of extreme conditions, air transportable via a Boeing 747 and deployed from a typical vessel of opportunity in all of their operating regions. The DDS is capable of 180 days’ continuous operation, delivering dispersant at 30 gpm at 5000psi in water depths up to 10,000ft. The system is compatible with all work class ROVs and can be configured to accommodate the specific parameters of a given well location.

To enable these features, SSW contracted and qualified Aberdeen-based HydraSun’s specialty hose, Interventor (OE: October 2015). The hose would be used as the primary means of delivering dispersant from the vessel to the subsea distribution reels located on the seabed. A number of other regionally sourced subsea dispersant applications have used coiled tubing, but after detailed analysis and fatigue testing, it was determined to go with HydraSun’s Interventor hose. The hose is custom designed, lightweight, and capable of withstanding the various chemicals, pressure, depth, flow, temperature and constant fatigue generated by vessel motion. After extensive design and testing, two 750m hoses, and four 600m hoses were constructed.

Clump weight termination assembly (CWTA).

Seanic Ocean Systems was commissioned to engineer and construct the supporting equipment that would be used both topside and subsea, and integrate the HydraSun Hose requirements into the DDS design. The scope included a deck mounted topsides system, an electric-powered hose winch, an overboard chute, and the dispersant pump skid. The subsea scope included a clump weight termination assembly (CWTA), two subsea hose deployment systems (SHDS) with dispersant wands.

On deck, the system is controlled by a control van outfitted with an integral electrical distribution panel for operating each piece of equipment. The control van also displays and records the pump skid fluid data including flow rate, pressures and temperatures. The control van is equipped with an emergency stop inside and out and is tied into the pumping skid which too, is equipped with manual shut off valves. It consists of redundant pump circuits (each at 30 gpm at 5000psi) that can be used simultaneously or independently. The triplex pumps are variable frequency driven, which is used to control output flow.

Interfacing between main supply hose through tugger winch on chute.

EMCE Winches, based out of Holland, were contracted by Seanic to engineer and manufacture the deck winch with specific requirements that included redundant 30hp motors, automatic levelwind, and a transpooling frame that can also be used for pre-tensioning the six interchangeable hose reels. Two of the reels have a pump through configuration and four have a trailing wire configuration, to keep consistent flow while changing out reels during operation. The overboard chute contains a small electric tugger winch, that works simultaneously with the deck winch, to aid in hose connections during deployment. The overboard chute has an adjustable platform, for changing clearance height depending on the vessel’s deck configuration. The main chute section is Wearlon-coated for protection of the main supply hose during deployment and operation. The CWTA is connected to the main supply hose via a 1.5in stab and incorporates an independent emergency disconnect system in the case of a drive off event and can be easily reconnected subsea via ROV. It also has topsides adjustable weights, (2000lb (min) to 5000lb (max)), depending on required working conditions. Once at targeted water depth, the CWTA is connected to the SHDS, resting on the seabed, with a 1in hose that extends out up to 250ft from the SHDS, providing the CWTA a range of movement above the seabed.

Another option is to connect the CWTA to an additional clump weight on the seabed via a tether. This would improve the system operability under harsh metocean conditions in deep waters. Each SHDS hose reel contains 1500ft of 1in hose with a dispersant wand at the end. The 1500ft hose is easily pulled out from the SHDS reel with an ROV and rewound back to the reel with a Class 1-4 torque tool. Accompanied with the tooling suite is a topsides storage van for all hoses, electrical wiring, and dispersant wands along with additional consumables, spares, and ancillary equipment. The system includes a power supplied and climate controlled workshop van, fully equipped with all tooling needed to operate the system, clearly marked for quick accessibility, which also includes spares.

The equipment was designed to meet stringent requirements that included a do not exceed size due to Boeing 747 cargo access and loading restrictions, and to incorporate cargo lashing that could withstand the expected g-force criteria.

Seanic Ocean Systems engineered and constructed the supporting equipment, all while coordinating and managing the teams with intricate schedules from around the world. This helped to ensure all testing were complete on time prior to staging the equipment for the systems integration test, which took place in Seanic’s in-ground test tank in Katy, Texas.

Steve Eggert began his career at Cameron as an interface design coordinator, specializing in subsea blowout preventer design and integration into deepwater drilling vessels. He has worked for Manatee Inc. for 15 years, providing firms, such as BP, with innovative solutions, project planning and execution leadership. Along with supporting BP’s emergency response efforts, he was awarded a patent on BP’s Offshore Fluid Transfer System, (Jan-30-2015).

Britni Plummer has over 15 years’ experience, specializing in subsea. For the past five years, Britni has lead custom engineered solutions, ROV tooling projects, for Seanic Ocean Systems. She is an active member of the Project Management Institute and with the local Houston Chapter.