Remotely Operated Vehicles involved in the Deepwater Horizon response Figure 1 Snapshot of the fleet showing the Discoverer Enterprise drillship in the centre, the Q4000 MODU at the top right, and the Viking Poseidon to the lower right. Source: Reuters The subsea activities being undertaken in response to the tragic incidents aboard the Deepwater Horizon semi- submersible mobile drilling unit (MODU) on April 20th 2010 have been performed by remotely operated vehicles (ROV). ROV are underwater robots powered and controlled from a surface vessel or platform via an umbilical. The ROV used are equipped with dual manipulators and are of a grouping known as “work-class” (WROV) as they perform the work that would have historically been undertaken by divers in shallow waters. The water depth at the Macondo well is approximately 1500m and although well out of the reach of divers, is not now considered especially deep when compared with some of the other oil and gas projects already in place or under development. All the WROV in use at the site are capable of working in depths of at least 3000m. Some autonomous underwater vehicles (AUV) are also being used to collect seawater samples and to map the extent of the oil in the water column. At the time of writing (end of June 2010), the situation at Macondo is that some fluid and gas is being diverted to the Helix Energy owned Q4000 semi-submersible MODU via a subsea manifold connected to the faulty blow-out preventer (BOP) that should have activated and sheared the drill pipe and sealed the well. Another connection has been made from the top of the BOP to the Transocean owned Discoverer Enterprise drill ship via a cap that has been secured to the newly cut drilling riser that projects from the top of the BOP. Relief wells are being drilled by a pair of Transocean platforms. To reach this stage, many operator and vehicle hours have been spent observing to enable the response engineers to assess the damage to the subsea infrastructure and to determine possible solutions. Some of the first WROV on scene were the two Schilling Ultra Heavy Duty (UHD) WROV operated by C- Innovation that were deployed from the Max Chouest ROV/platform support vessel and that attempted to activate the BOP. The attempt to activate the BOP involved the WROV providing hydraulic pressure via a connecting hose that (if all was working properly) force the BOP shear to cut through or crush the drill-pipe. The UHD has a 200HP hydraulic power-pack that is used to power its thrusters and has an additional power-pack of up to 75HP to power tooling. The 3m long, 2m high vehicles weigh 5000kg in air and are available with depth ratings of up to 4000m. 50 UHD vehicles have been built to date since starting production in 2007 and are predominantly owned by operators with large vessel fleets such as C-Innovation (the ROV division of Gulf of Mexico support company Edison Chouest Offshore), and Bourbon Offshore. Figure 2 Shilling UHD Source: Schilling Figure 3 C-Innovation UHD 05 attempting to activate the Deepwater Horizon BOP Source: BP/C-Innovation/USCG The most powerful WROV on site is the Oceaneering Maxximum WROV that has a 300HP hydraulic power- pack, and is hosted onboard the Ocean Intervention III ROV support vessel that is owned by Island Offshore on a long term lease with Oceaneering. The other WROV on the vessel is a 150HP Oceaneering Millennium vehicle, and both have depth ratings of 3000m. Many WROV are deployed directly from a host vessel with their power and control umbilical being supported at one end by the vessel and the other end by the WROV. In deep-water, the necessary length and thickness of umbilical to reach from the surface and give the vehicle sufficient working range whilst at depth would mean that the vehicle would have to be equipped with extra buoyancy and thruster power. Instead, deep-water ROV are connected to a lightweight umbilical (known as a tether) of up to 900m in length that is in turn connected to the thicker, heavier primary umbilical that reaches to the surface vessel via a tether management system (TMS). The ROV is launched and recovered attached to the TMS either in a cage-type garage or attached via a locking latch system to a top-hat style TMS. On modern, dedicated ROV support vessels such as the Ocean Intervention III used by Oceaneering to deploy their Maxximum WROV, the TMS and ROV is deployed via an extendable arm that brings the vehicle from its resting position inside the vessel to a point well clear of the side of the vessel where there is less risk of impacts during the launch or recovery process in heavy weather than would the case is a through the hull “moon-pool” was used. Figure 4: Oceaneering Hydra Maxximum in TMS Figure 5 Ocean Intervention III with WROV launch cage arm extended Source: Oceaneering Source: Island Offshore The WROV at the site have performed a wide range of duties with their manipulators and onboard tooling but they are also used to position and provide power to tools that are suspended from the surface vessels. In the early days of the response, this included the insertion of a collection tube into the broken riser – the tube was connected to the Transocean Discoverer Enterprise drillship. The WROV were then used to install a subsea manifold that connected to the BOP to allow the “top-kill” and “junk-shot” procedures to be attempted. A number of containment cap solutions designed to rest over the damaged riser and BOP were attempted but failed due to the build up of hydrates that effectively blocked the flow. What has now been seen as the most successful operation in the response was the cutting and removal of sections of the damaged riser pipe from the BOP so that a more effective collection cap could be fitted to the BOP and allow for much greater recovery volumes. The lower marine riser containment (LMRP) cap contains methanol injection lines that are used to reduce the build up of hydrates, and the structure has a rubber grommet that prevents leaks when compressed. Figure 6: The Genesis XP2500 shears used Source: Genesis Attachments Figure 7: Cutting riser with diamond band saw Source: BP The first cut on the riser was made using a set of hydraulic shears from Genesis Attachments that weigh around 25 tonnes and that can exert 29,000kN of force. The second cut – at the top of the BOP was achieved using a diamond coated band saw from Cutting Underwater Technologies. This technology is already used in the decommissioning of redundant oil and gas platforms. The cutting tool was manoeuvred into place by a WROV and locked itself onto the BOP. The continuous diamond coated cutting band is mounted on a series of pulleys that are move into position once the tool is securely in position. Hydraulic power and control for the tool is provided via the ROV. The LMRP cap was installed on the 3rd of June and takes oil and gas to the Discoverer Enterprise drill-ship where oil is collected and gas is flared. A second system, which began operations on the 16th of June , takes oil and gas from the BOP via the subsea manifold to the Q4000 semi-submersible where both oil and gas are flared. This followed calls for increased redundancy in the recovery operations that resulted from a shut-down caused by a lightning strike on the drillship. Recovery operations were interrupted again when a WROV accidently closed one of the pressure relief vents on the LMRP during a manoeuvre. This required the LMRP to be brought to the surface, repaired and re-installed during a 10 hour operation on the 24th June. The next step is to install a buoyed riser system that will be disconnectable in the case of severe surface weather conditions, and will recovery oil and gas to the Helix Producer 1 floating production vessel (owned by Helix Energy Solutions) from the subsea manifold currently used by the Q4000. Figure 8 Q4000 MODU Figure 9 Venom ROV Source: MarineLog Source: SMD The physical demands on both WROV and their operators in this response are far greater than would normally be the case for drill support operations due to the sheer amount of dive time needed and the understandable pressure from the public and the US government. Whilst the provision of live feeds from ROV cameras has allowed a rare glimpse into the previously hidden and unknown world of subsea operations, any interruption in the broadcast is met with media fuelled cries of cover-up and conspiracy, which puts even more pressure on the personnel involved. Only once the leaking well is finally sealed, and an analysis of both the incident and the response undertaken will the real implications on the people, environment and industry in the Gulf of Mexico be understood. Autonomous Underwater Vehicles involved in the Deepwater Horizon response Figure 11 Teledyne Webb Research Slocum Figure 10 Bluefin-21 with Gulper system Glider “Waldo” owned by Rutgers University Source: MBARI Source: US National Parks Service A number of scientific AUV have been deployed in an attempt to map the spill and to take samples from within the water column to detect and measure levels of oil and chemical dispersants. The Monterrey Bay Aquarium Research Institute is working with the US National Oceanographic and Atmospheric Administration (NOAA) and have deployed a Bluefin Robotics “Bluefin-21” AUV from the NOAA Ship Gordon Gunter fitted with a “Gulper” water-sample acquisition system.