Facts, Figures and Explanations Production - How Crude Oil and Gas are Extracted Undersea View Click on the thumbnail to view a larger image If large deposits of crude oil and gas are found, the company must apply to the Government to develop the oil field and bring it into production. The average time between discovering an oil field in the North Sea and piping oil ashore is five years. During that time various stages before production are gone through. Companies developing new offshore fields have three main options: A Fixed platform The legs - made either of steel or concrete - are known as the jacket and take about 2 years to construct. Many are made in Scotland. They are built on land and then floated out to their location over the wells which have been left by the appraisal-drilling unit and secured to the seabed by large steel pins. The accommodation, drilling and production facilities pad for helicopters to land on - known as the top-sides - are also built onshore, then towed out on a barge. These modular parts are lifted into position by a massive crane barge. Fixed platforms can operate in water depths of up to about 400 metres. Floating production facilities These are designed either like a semi-submersible drill rig or like a conventional ship. They are useful for smaller finds because they can be moved and used again elsewhere when the field is no longer producing. However because floating production platforms are less able to cope with heavy storms, production is more likely to be suspended during adverse weather conditions than it would be using a fixed platform. Underwater production facilities These are a series of seabed wellheads controlled remotely from a nearby fixed platform. This innovative method of production has been developed almost entirely because of the conditions in the North Sea. Companies have tried to find ways of making the best use of their existing fixed platforms and by searching surrounding areas have sometimes found lots of small reservoirs. An underwater wellhead is installed to produce oil and gas from these small reservoirs which is then piped back to the platform for processing and transportation to shore. This means that small oil and gas deposits can be recovered. Oil Platforms Oil platforms are really industrial towns at sea. In addition to drilling the other main functions of an oil platform are: Preparing water and gas for injection into the reservoir - to maintain pressure. Processing the crude oil, which is a hot, frothy, corrosive, high pressure liquid. Pumping the oil ashore. Providing all the necessities of everyday living for those who work in the harsh environment of the North Sea. An oil rig which is a smaller, mobile structure is used for drilling exploration wells and should not be confused with a production platform that accommodates all the activities explained above. A production platform operates 24 hours a day for 365 days a year. It has three main sections: Accommodation area This includes cabins, canteens, recreational facilities and offices as well as a helicopter pad for flying staff on and off the platform. There are about 26,000 people working offshore in UK waters at any one time. Whilst some platforms have up to 100 people working on them, others are unmanned. Generally when people are on a platform they work a 12 hour shift and then have 12 hours rest. Depending on their job, they may either work two weeks offshore followed by two weeks at home or three weeks offshore with two weeks leave. Supply boats constantly shuttle from shore to the platforms taking in supplies and bringing away refuse. Wellhead/drilling module This contains the derrick, drill floor and wellheads. Each well has a specific function: it may be a production well, a water injection well, through which water is pumped down into the reservoir; or a gas injection well to pump gas back down into the reservoir. These methods are used to get more oil out of the reservoir. Crude oil is naturally forced to the surface because it is under pressure in the reservoir. However, as the field gets older there is less pressure so water or gas has to be pumped down the injection wells to increase the pressure and force the crude oil up. Process facilities - are used to separate crude oil, gases and water What comes out of the well is a mixture of crude oil, gas and water and so needs to be separated before being transported to shore. The water is cleaned and then either pumped back into the sea or injected back into the reservoir to maintain pressure. The gas is compressed and piped back to shore or injected back into the reservoir to increase pressure. Some of the gas is used as fuel for the platform generators. Safety With so many people working in potentially dangerous situations, nothing is left to chance where safety is concerned. Highly trained safety managers are employed to make sure that all safety equipment - lifeboats, fire-fighting equipment, smoke hoods etc - is in good working order. Everyone who goes offshore receives safety training, even day visitors. Regular offshore workers must pass a medical and complete a fire-fighting and survival course that teaches them what to do in an emergency. Because offshore workers travel to work by helicopter, they also have to learn how to survive if the helicopter has to ditch in the sea. Part of this involves escaping from the helicopter and they practice how to do this by being lowered, in a simulated helicopter, into a special water training tank. On all platforms safety exercises and drills are carried out on a regular basis. Each manned platform will always have a standby ship which, in an emergency, will pick up workers and care for them until help arrives. Facts, Figures and Explanations Index

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