New Platforms Design Withstand North Sea Conditions

The pressure to reduce the cost of new developments has never been greater for North Sea operators. The combination of low oil prices, decreased North Sea development opportunities and increased competition from the U.S. shale industry means the industry is being forced to adapt to new ideas.

One development concept that is starting to gain traction is the use of low-cost wellhead platforms for the development of small satellite fields. These are typically newly discovered fields close to an established host platform, which can provide control and power and also carry out fluid processing. Although wellhead platforms have long been a favorite in the shallow waters of the southern North Sea, up until now the preferred option for the development of satellite fields in deeper water has been to use a subsea manifold with a tieback to the host facility. Subsea manifolds are tried, tested and trusted, but WorleyParsons has carried out several studies showing that subsea manifolds don’t necessarily provide the best value solution for a multiple well development. The difficulties and additional costs associated with maintenance and future well intervention operations can all contribute to increased costs over the lifetime of a project.

WorleyParsons has accumulated a reference list of more than 500 installations that are currently operating throughout the world, and its team has combined its experience with ideas borrowed from the shale industry—where standardization and modularization of equipment is the key to low-cost field development. The company has come up with a new concept in wellhead platforms suitable for installation in deeper water and able to withstand North Sea conditions.

The new design uses piled foundations, can be deployed in water depths of up to 120 m (394 ft) and provides space for a maximum of 12 well slots. No accommodation has been provided for personnel, who will gain access for four monthly maintenance visits by vessels equipped with a “walk-to-work” gangway. The platform design includes a 5-tonne crane and sufficient deck space to allow full access for future well intervention. WorleyParsons also has designed the new platform for construction in its covered yard near Stavanger, Norway, with one flat side to permit installation by either barge launch or jackup platform to widen the choice of installation contractor.

The platform is designed with a “design once, build many” approach to capture economies of scale and efficiencies more closely associated with a production line than a North Sea construction yard. The design borrows from the philosophies that WorleyParsons has previously followed in the Persian Gulf and Gulf of Thailand and uses a minimum number of different profiles to reduce procurement and stockholding costs.

Topsides and jacket weights are comparable to more traditional North Sea designs at about 650 tonnes and 3,500 tonnes, respectively, for a 100-m (328-ft) water depth platform, with almost all of the topsides and much of the jacket being identical for any platform regardless of water depth. However, there is scope for significant savings in project schedule by both reducing setup times and by allowing construction to start in parallel with detailed design. The design is so standardized that water depth, seabed conditions and well slot arrangement are the only pieces of information required to completely define an individual platform, further reducing project schedule and minimizing construction risk.

WorleyParsons sees an immediate market for at least 20 lowcost modularized platforms in the Norwegian sector of the North Sea alone and is talking to several operators who have been carrying out studies to assess their viability. They also see applications in U.K. waters, where the upcoming 30th licensing round will be targeting small pool discoveries that will require especially low-cost development schemes.

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Drilling Riser for Offshore Rig

A drilling riser is a large pipe or duct used to encapsulate drilling equipment during underwater operations. These risers allow workers over the surface of the water to drill deep into the bottom of the sea. A drilling riser is commonly used to drill for oil under the sea, or just to explore the bottom of the sea and the ground below. After the tube has been placed in water, the drill itself drops down through the center of the duct to access the seabed.

Companies can choose between two basic types of drilling risers depending on the needs of each application. Marine punching risers are used with floating platforms or boats, and include an explosive preventer placed under the surface of the water. When working from a fixed oil platform, companies rely on tie-back drilling rigs. These systems include blowout preventer located at sea level, which protect workers and equipment from pressure variations or potential explosions.

A drilling riser can end at the bottom of the sea, or it may extend a little in the ground to prevent water infiltration. The tip itself and all the associated equipment pass through the upright and continue below the surface of the earth. Without these risers in place, the drill would be vulnerable to corrosion and damage caused by salty water. All cuts of rock and other debris would simply be released into the water, resulting in pollution that could have an impact on the quality of water and sea life. Drilling risers helps to contain drilling operations within the duct boundaries.

During sub-sea drilling, workers pump down drilling fluid down through the drill line into the cutting bit at the end. This spray fluid spray out of the bit to help reduce the heat generated by cutting through stone and hard ground. This fluid then carries rock and other debris back through the duct to the surface of the sea, where it can be harvested and treated by oil workers. The drilling riser should be slightly larger than the drill itself to make room for this fluid.

The use of puncture posts enables water drilling companies for long periods, with little risk of damage to the equipment. The tip can be left in place over time without being exposed to sea water, allowing workers to dig deeper than in previous years. Bringing waste and rocks to surface for disposal, the risers help to reduce water pollution and its effects.

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What is Offshore Drilling ?

Offshore oil extraction is an oil extraction technique that allows petroleum companies to access oil deposits buried beneath the ocean floor. Mostly, offshore drilling sites are located on the continental shelf, though drilling technology advancements have made even more economically and physically feasible sea platforms. Many people oppose offshore oil extraction, due to concerns about its impact on the environment, and effectively the imperfections of oil platforms off the coast.

Many sections of the Earth's oceans have massive oil deposits buried deep beneath the surface, and these petroleum deposits are extremely attractive to many oil companies. The first offshore oil drilling operation was founded in 1938 in the Gulf of Mexico, and other manufacturers have quickly started to follow the example of other regions of the world. Since 1970, many communities have issued specific prohibitions against offshore drilling, and the problem has become the source of discord in some areas.

There are several ways in which you can run an oil offshore drilling operation, and the type of rig oil used is usually dependent on the depth in position, type of oil, and prevailing conditions. Classicly, fixed installations are integrated into the ocean floor, with heads and more parts and adjustable to allow oil extraction technicians from the surrounding area. Floating plants are also used in some regions, and in some areas offshore oil extraction is also carried on ships for greater mobility.

Working on an offshore drilling rig can be extremely dangerous. Several accidents have caused plants to explode, overturn, or become severely damaged, accompanied by loss of life, and many crews are now housed out of the home so that if something happens to the rig, the loss of life will be less serious. Workers on oil platforms still have to deal with adverse weather conditions, problems with the drilling rig, and geological conditions that could become dangerous and are generally well paid in recognition of the risks of the industry.

The environmental effects of offshore drilling are mainly caused by pollution related to poor maintenance and management facilities. Oil spills around drilling rigs are common, especially at the bottom of the sea, where drilling can stimulate infiltration, and heavy metal pollution may also occur. Some people think it disrupts offshore oil rigs and confuses marine life, although ironically plants can also provide shelter for sea birds and fish.

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Drilling Rigs Type

There are many different types of drilling rigs. Which rig selected depends on the specific requirements of each drill site. Roll your mouse over each picture to see what kind of rig it is.Its a good for drilling knowledge

Land Based Drilling Rigs - The land-based drilling rig is the most common type used for exploration. This site is using a conventional, land-based drilling rig that is smaller and more efficient than those used in the past.

Slim Hole Drilling Rig - A conventional drill bore might be 18 inches in diameter; a slimhole bore can be as little as 6 inches. A slimhole well drilled to 14,760 feet may produce one-third the amount of rock cuttings generated by a standard well. The size of the drill site can be as much as 75 percent smaller, since slimhole equipment requires less space than conventional equipment. However, slimhole drilling is not technically feasible in all environments.

Coiled Tubing Drill Rig - Conventional wells are drilled using sections of rigid pipe to form the drill string. In some cases, coiled tubing technology can replace the typical drill string with a continuous length of pipe stored on a large spool. This approach has many benefits, including reduced drilling waste and minimized equipment footprints, so it is especially useful in environmentally sensitive areas. This technology is best suited to re-entering existing wells, and when multiple casing wells are unnecessary.

Jackup Drill Rigs – These rigs may be used in relatively shallow water -- less than 300 feet deep. A jackup rig is a floating barge containing the drilling structure that is outfitted with long support legs that can be raised or lowered independently of each other. The jackup, as it is known informally, is towed onto location with its legs up and the barge section floating on the water. Once at the drilling location, the legs are jacked down onto the seafloor, and then all three legs are jacked further down. Since the legs will not penetrate the seafloor, continued jacking down of the legs raises the jacking mechanism attached to the barge and drilling package, and slowly lifts the entire barge and drilling structure to a predetermined height above the water. These rigs are extremely strong, since they have to withstand ocean storms and high waves. These rigs are moved by simply by moving the legs up and down, which makes them cost-effective and easily shifted out of harm's way during storms.

Semi-Submersible Rigs – Drilling in water deeper than 300 feet demands some kind of floating platform to hold the rig. Semi-submersible rigs are floating vessels supported on large pontoon-like structures that are submerged below the sea surface. As with jackup rigs, the operating decks are elevated as much as 100 or more feet above the pontoons on large steel columns. This design has the advantage of submerging most of the area of components in contact with the sea and minimizing loading from waves and wind. Semisubmersibles can operate in a wide range of water depths, including deep water. Semi-submersibles can either be attached to the ocean bottom using strong chains and wire cables or may utilize dynamic positioning to remain stationary during drilling without anchors.

Drill Ship - For exploration targets farther offshore, specially designed rigs mounted on ships can drill a well in water depths up to 10,000 feet. These rigs float and can be attached to the ocean bottom using traditional mooring and anchoring systems, or utilize dynamic positioning to remain stationary during drilling without anchors.

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