Necessity is the mother of invention

21/12/2009

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It is widely acknowledged that there will be a continued and long-term growth in demand for energy. By 2050 it is predicted that there will be one billion – or double the current number – of cars on the road. This figure alone demonstrates the scale of the energy challenge facing the world.

To meet such demand – as well as to address the challenges of climate change – we will need energy from multiple sources: biofuels, gas, hydrogen, diesel, solar, nuclear and oil. Indeed, it is true that we are at the start of a fundamental shift in our energy system whereby we become increasingly powered by alternative energies and cleaner fossil fuel. It is also true that it is becoming increasingly difficult to access ‘easy’ oil: North Sea production has been in decline since 1999. Yet sourcing new supplies of oil and gas has a crucial role to play in both enabling the world to meet rising demand but also in securing a successful transition into a world which is less fossil fuel dependent.

Innovative technology
Pressure on the oil and gas industry to push the boundaries of technological advancement to locate and source new supplies has therefore never been greater. Recent finds of new supplies all share one of two common traits: they are in more remote and harder-to-reach places than ever before or subsurface conditions are too formidable to enable the resources to be extracted economically at today’s prices. Companies are attempting to drill in deeper water than previously thought possible and corporate scientists are tasked with devising and deploying increasingly sophisticated and innovative technology to make supplies accessible.

As the search for oil and gas takes the industry into new locations, offshore production facilities are now being developed in what specialists call the ultra-deepwater. Such extreme engineering can be found off the coast of the Gulf of Mexico, where Shell is using advanced technology to access previously unreachable oil and gas. 320km from the Texas coastline, the 45,000 ton Perdido floating oil rig can be found sitting alone on the ocean’s surface, attached to the sea floor by nine mooring lines that stretch for 3,000m. When the Perdido platform starts producing oil and gas – or as industry engineers would say, goes on-stream in early 2010, it will tap into three oil fields and will be the deepest offshore drilling and production facility on the planet.  

Perdido is expected to produce around 100,000 barrels of oil and 200,000 cubic ft of gas per day. It will operate in water which is about 2,380m deep and tap into oil and gas reservoirs that lie a further 2,380m beneath the seabed. It was only as recently as 1996 that the industry was able to operate in depths of between 610m and 914m of water. The size of the structure, the fact that the area is prone to devastating hurricanes, the depth of the water and even the pressure within the oil and gas reservoirs themselves have required cutting∞edge technology to make accessing the hydrocarbons possible.

Engineering feats
Assembly of the rig itself was the first challenge facing the engineers working on the project. The Perdido oil rig was floated to its remote ocean location. The vast assembly operation first involved flipping upright in the water the cylindrical spar that provides the rig’s buoyancy and then, seven months later, using a floating crane to lift the 10,000 ton upper deck into place.

A 50,000 ton, 170m long spar – or in layman’s terms, a giant floating cylinder – was then put in place and sits below the ocean’s surface. The spar had to be towed 13,200km from Finland via Texas, where it was fitted for offshore installation, before continuing its journey to its permanent location in the Gulf of Mexico. Here it was secured to the seafloor by the nine chain and polyester mooring lines, spanning an area of the seafloor roughly the size of downtown Houston. By adjusting the tension on the mooring lines, the spar can move around an area of water equivalent to the size of a football pitch and position itself directly above any of the site’s 22 individual wells from which the oil and gas is sourced beneath the facility. The ability to move the spar is critical as it also allows the platform to locate itself in the safest possible location during potentially damaging storm conditions.

Subsea separation
Once in position, the next technological hurdle to overcome was actually extracting the oil and gas from the reservoir, a task made more difficult due to the fact that the pressure within the oil and gas in the reservoir is low. To physically move the hydrocarbons to the surface required (or ‘requires’) the development of a subsea boosting system to supplement the low pressure and pump the oil and gas to the surface.  At the same time, the system employed also undertakes an initial processing of the resources on the seabed itself – something novel to the industry. This process separates out the wanted oil and gas from the unwanted water and other elements that are produced from each well meaning the efforts of the boosting system are not wasted. The oil and gas from the site’s 35 wells is sent to a sump 107m below the sea’s surface where another pump then sends it to the surface.

Robots on the seafloor
The final challenge lay in actually transporting the oil and gas back to land. To enable the oil and gas to be transported by pipelines back to the mainland, Shell deployed the groundbreaking technology of subsea robotics. These remotely operated vehicles (ROVs) – which are controlled by engineers at the surface – were able to carry out complex ‘manual’ tasks, such as securing nuts and bolts and using saws to cut sections from pipes. At Perdido, the ROVs were used to install materials that enabled the structure to connect to a pipeline 123km away at a depth of over 1,372m – from which the oil and gas was moved to dry ground.

Perdido is the deepest oil drilling and production platform in the world and boasts the deepest subsea well in the world. To meet the world’s energy demands, further world records will inevitably have to be broken in the years to come. Technological advance and innovation has always been an important pillar of a successful economy, but this sentiment rings truer now in the oil and gas industry than it ever has before. Oil and gas remain a vital part of the world’s energy mix, and only by pushing the boundaries of scientific innovation will a secure energy future be realised.

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