Tom Newsom has asked me to write a bit about my job, so here goes. I am an ex aircraft engineer and I work with remotely operated vehicles, or ROV’s, in the oil and gas industry.
The image that most people have of the oil business is of a solitary nodding donkey on an arid plain in Texas or the Middle East. The truth couldn’t be further away from this. Most of the world’s oil reserves lie beneath the seabed at the bottom of the ocean. A desert, certainly, but far from arid.
There are many oilfields off the coast of West Africa. Nations like Angola, Equatorial Guinea, Nigeria, Republic of Congo and Ghana are the major stakeholders in terms of the rights to these. The fields are owned and operated by companies like BP, Total, Agip and Mobil.
Typically a subsea oilfield is spread over an area of several kilometres and is composed of many wells that are tied back to an FPSO. An FPSO (Floating Production and Storage Offshore) is essentially a very large vessel used as a pumping station and storage facility for the crude that is extracted from the wells. Tankers arrive on a regular basis to take this away. On some FPSO’s, processing of the crude is carried out as well. Many of the older types are converted tankers. The newer ones are purpose built and have to be seen to be believed, they are vast, like floating cities.
Getting the oil from many miles deep beneath the seabed to the FPSO is a major technological feat. A large number of wellheads are connected by flowlines to manifolds which then route the oil to production risers. These large flexible pipelines run for many kilometres and then may rise 2 kilometres or so to the surface. The underwater infrastructure is complex and the structures are massive. Wells and manifolds are the size of buildings on land. They are fed with control signals and power by umbilicals from their FPSO. All of this takes place at a depth of 1200 to 2000 metres.
Naturally all of this infrastructure has to be built and maintained. This is where Remote Operated Vehicles and subsea intervention technology comes in. It would be physically impossible for a diver to work at depths of 1000 metres plus. Hence everything is designed and engineered for the ROV to work with. ROV’s are involved at every stage of the process, from drilling the well, installing the wellhead, installing manifolds and other structures, laying pipelines and repairing the installations afterwards.
A typical ROV weighs about four tons in air. Power outputs vary but typically are in the region of 100 to 150 HP. An aluminium frame forms the foundation and syntactic foam provides buoyancy. A 3000 volt subsea electric motor drives a hydraulic pump to give the muscle. 1200 volts is a typical instrument supply, transformed down to 110 and 24 volts. The voltages are so high to prevent losses in the umbilical from the surface, and to keep the conductor size manageable. Data in the form of 8 video channels and RS485, 232 and 422 comes up and down from control, cameras and sensors via a single mode fibre optic link and multiplexer.
Most vehicles are fitted with four axial vectored thrusters and four vertical thrusters. Two manipulators are standard. A five function arm on the left side of the vehicle is used for moving heavy rigging, holding on to structures and clearing boulders etc. On the right side is mounted a dextrous, powerful 7 function manipulator, typically a Schilling Titan 4. This is fully servoed and is used for more intricate tasks. Both arms are hydraulically powered and can lift close to half a ton.
British technology and expertise leads the field in subsea intervention. The vehicles I work on are built by a UK company not far from York. This is the true hidden success story of UK industry and the true powerhouse of the UK economy.
The company I work for has it’s UK headquarters in Aberdeen. It has offices on all continents and I have worked on projects from inside the Arctic circle to Australasia. Trips on board the ship tend to be of 6 week duration, with 6 weeks off afterwards. We work in two shifts 12 hours a day 7 days a week. The work involves maintaining and repairing the vehicles and modifying them to do the tasks set before us. We also take care of all the subsea tooling required for the job. If we come across a subsea problem we make a tool to cope with it. The other half of the job is piloting the vehicles to get the operational task done.
An illustration of the types of the scale of the fields and type of work can be given by a project I worked on in 2014/2015. The Girrassol field off the coast of Angola contains 94 million tons of proven oil reserves. Most of this is brought to the surface up a vertical riser structure that is 1.2 km high. On top of it is a mid water arch for guiding pipelines up to the FPSO. This is a structure taller than the Burj Khalifa in Dubai with an arch the size of the Sydney Harbour bridge on top of it, all under the ocean. The riser is supplied from several rigid pipelines. These had been in place since 2002, and had begun to fail through cracking. We cut these up with a diamond wire hydraulic saw, removed the sections, disconnected the terminations and then replaced them with flexible lines. This job called for large amounts of tooling and was very ROV intensive.
Life on board ship is split into periods of work and rest. We all get on very well and I consider those I work with to be my brothers. They have supported me through some of the darkest times of my life. We have a fairly decent internet connection and so contact with home can be made quite easily, by phone, email and skype etc. A lot of the guys I work with are ex military engineers, myself included.
Hopefully I have given you some idea of what it is I do. I shall put up another post shortly with some photographs.
Cheers,
Carl.