Deepwater drilling, or Deep well drilling, is the process of oil and gas exploration. There are approximately 3400 deepwater wells in the Gulf of Mexico with depths greater than 150 meters.
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It has not been technologically and economically feasible for many years, but with rising oil prices, more companies are investing in this area. Major companies working in this sector include Halliburton, Diamond Offshore, TransOcean, Geoservices, and Schlumberger. The deepwater gas and oil market is back on the rise after the disaster of 2010, and total expenditure of around $35 billion per year and a total global Capex of $167 billion in the past four years.
Recent industry analysis by Visiongain has estimated that the total expenditure in the global deepwater infrastructure market would reach $145bn in 2011.
“Not all oil is accessible on land or in shallow water. You can find some oil deposits buried deep under the ocean floor.” ...Using sonic equipment, oil companies determine the drilling sites most likely to produce oil. Then they use a mobile offshore drilling unit (MODU) to dig the initial well. Some units are converted into production rigs, meaning they switch from drilling for oil to capturing oil once it's found. Most of the time, the oil company will replace the MODU with a more permanent oil production rig to capture oil.” ...The MODU's job is to drill down into the ocean's floor to find oil deposits. The part of the drill that extends below the deck and through the water is called the riser. The riser allows for drilling fluids to move between the floor and the rig. Engineers lower a drill string – a series of pipes designed to drill down to the oil deposit – through the riser.” “The expansion of deepwater drilling is happening despite accidents in offshore fields...”In the Deepwater Horizon oil spill of 2010, a large explosion occurred killing workers and spilling oil into the Gulf of Mexico while a BP oil rig was drilling in deep waters.
“...Despite the risks, the deepwater drilling trend is spreading in the Mediterranean and off the coast of East Africa after a string of huge discoveries of natural gas.” “The reason for the resumption of such drilling, analysts say, is continuing high demand for energy worldwide.”Types of Deepwater Drilling Rigs
There are basically two kinds of mobile deepwater drilling rigs: semi-submersible drilling rigs and drillships. Drilling can also be performed from a fixed-position installation such as a floating spar platform (or tension-leg platform).
- Fixed Platform- Fixed Platforms consist of a tall, steel structure that supports a floating deck. Because the Fixed Platform is anchored to the sea floor, it is very costly to build. Its maximum depth it can drill to is 500 meters (1,600 feet) below the surface.
- Jack-Up Rigs- Jack-up rigs are mobile platforms that are used for more shallow or non-permanent oil deposits. This platform can be moved around, and the legs are then lowered to the sea floor and lock into place. The legs rise above the water, meaning the platform is raised up out of the water. That makes this type of rig safer to work on, because weather and waves are not an issue.
- Compliant-Tower Rig- The compliant-tower rig is very similar to the fixed platform. Both are anchored to the sea floor and both work places are above the surface. However, the compliant tower is taller and narrower, and can operate up to 1 kilometer (3,000 feet) below the surface.
- Floating Production System- the Floating Production System is the most common rig used in the Gulf of Mexico. This rig is buoyant, meaning the bulk of it is floating above the surface. However, the wellhead is located on the sea floor, so extra precautions must be made to prevent a leak. A contributing cause to the oil spill disaster of 2010 was a failure of the leak-preventing system. These rigs can operate anywhere from 200 to 2,000 meters (660 to 6,560 feet) below the surface.
- Tension-Leg Platform- The Tension-leg Platform consists of a floating structure, held in place by tendons that run down to the sea floor. These rigs drill smaller deposits in narrower areas, meaning this is a low-cost way to get a little oil, which attracts many companies. These rigs can drill anywhere from 200 to 1,200 meters (660 to 3,940 feet) below the surface.
- Subsea Systems- Subsea Systems are actually wellheads, which sit on the sea floor and extract oil straight from the ground. They use pipes to force the oil back up to the surface, and can siphon oil to nearby platform rigs, a ship overhead, a local production hub, or even a faraway onshore site. This makes the Subsea system very versatile and a popular choice for companies.
- Spar Platform- Spar Platforms use a large cylinder to support the floating deck from the sea floor. On average, about 90% of the Spar Platform's structure is underwater. Most Spar Platforms are used up to depths of 1 kilometer (3,000 feet), but new technology can extend them to function up to 3,500 meters (11,500 feet) below the surface. That makes it one of the deepest drilling rigs in use today.
2010 Gulf Oil Spill Disaster
On 20 April 2010, a BP deepwater oil rig (Deepwater Horizon) exploded, killing 11 and releasing 750 000 cubic meters (200 million gallons) of oil into the Gulf of Mexico. With those numbers, many scientists consider this disaster to be one of the worst environmental disasters in the history of the US.
A large number of animal deaths have resulted from the release of the oil. A Center study estimates that over 82,000 birds; about 6,000 sea turtles; and nearly 26,000 marine mammals were killed from either the initial explosion or the oil spill.