14-08-2012, 01:38 PM
OFFSHORE DRILLING
offshore drilling.docx (Size: 682.53 KB / Downloads: 44)
INTRODUCTION
Oil and natural gas are brought to the surface from underground reservoirs through wells that have been drilled and completed to produce these fluids safely and economically. Fundamental technology of drilling, completion and production of oil and gas is common to onshore and offshore areas. But environmental conditions of a field affect facilities and engineering works of the field. Offshore areas produced 20-30 % of the oil and gas supply. Oil and natural gas accounted for about 65% of the world energy supply.
OFFSHORE DRILLING.
Offshore drilling refers to a mechanical process where a wellbore is drilled through the seabed. It is typically carried out in order to explore for and subsequently produce hydrocarbons which lie in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the continental shelf, though the term can also be applied to drilling in lakes, inshore waters and inland seas.
Drilling offshore, in some instances hundreds of miles away from the nearest landmass, poses a number of different challenges over drilling onshore. The actual drilling mechanism used to drill into the sea floor is much the same as can be found on an onshore rig. However, with drilling at sea, the sea floor can sometimes be thousands of feet below sea level. The earlier offshore drilling was limited to coastal oil deposits that were accessible from piers, but oil companies today can choose from a variety of elaborate methods, letting them drill almost anywhere at almost any depth. Since the land that is going to be drilled cannot provide a base for offshore drilling as it does for onshore drilling, an artificial platform must be created. This artificial platform can take many forms, depending on the characteristics of the well to be drilled, including how far underwater the drilling target is. Oil-drilling technology is constantly improving, and some rigs combine elements from different models to achieve specific abilities.
DIRECTIONAL AND HORIZONTAL DRILLING
Directional drilling is an exciting extraction technique in onshore and offshore drilling in that previously inaccessible reservoirs, long and thin reservoirs and reservoirs under shallow lakes can be reached after drilling at least 2,000 feet into the ground. With just one rig, 20 or more wells can be drilled, making it an economically productive technique.
Horizontal drilling, unlike directional drilling, can make a 90-degree turn after drilling only a few feet into the ground. Among the three main types of horizontal wells (short, medium and long radius), long radius is a good choice for offshore drilling, as these wells can have curvature radii of 1,000 to 4,500 feet with horizontal extension capability of 15,000 feet. A single drilling in the middle of a remote expanse of water can therefore be quite effective and practicable.
ROTARY DRILLING
Another dual-purpose, onshore and offshore drilling method is rotary drilling, or use of a rotating drill bit to dig into the earth. Rotary drilling consists of four key types of equipment: prime movers, hoisting equipment, rotating equipment and circulating equipment.
Prime movers give power to all the other pieces of equipment, whether through diesel or natural gas engines or turbines. Hoisting equipment helps lift and lower the rotating equipment in the event those parts need to be replaced. The rotating equipment, consisting of a drillpipe, the drill bit and drill collars, does the actual drilling. Circulating equipment is needed to cool down and lubricate the drill bit, remove debris, control pressure and slather the machinery with "mud," or drilling fluid. A blowout preventer located underneath the rig also helps seal the well in the event that the drilling fluid is unable to control any surges of upward pressure emanating from the oil and gas below.
TYPES OF OFFSHORE OIL RIG
The earliest offshore drilling was limited to coastal oil deposits that were accessible from piers, but oil companies today can choose from a variety of elaborate methods, letting them drill almost anywhere at almost any depth. From roving, computer-controlled contraptions to giant "spar" platforms held up by 10,000-foot poles, today's deepwater rigs are going far beyond anything their offshore forefathers could have imagined.
HISTORY
Around 1896, the first submerged oil wells in salt water were drilled in the portion of the Summerland field extending under the Santa Barbara Channel in California. The wells were drilled from piers extending from land out into the channel.
Other notable early submerged drilling activities occurred on the Canadian side of Lake Erie in the 1900s and Caddo Lake in Louisiana in the 1910s. Shortly thereafter wells were drilled in tidal zones along the Texas and Louisiana gulf coast. The Goose Creek Oil Field near Baytown, Texas is one such example. In the 1920s drilling activities occurred from concrete platforms in Venezuela’s Lake Maracaibo.
One of the oldest subsea wells is the Bibi Eibat well, which came on stream in 1923 in Azerbaijan.[3][dubious – discuss] The well was located on an artificial island in a shallow portion of the Caspian Sea. In the early 1930s, the Texas Co., later Texaco (now Chevron) developed the first mobile steel barges for drilling in the brackish coastal areas of the Gulf of Mexico.
OFFSHORE DRILLING SCENARIO IN INDIA
Brazil continues to be the brightest spot in the worldwide rig market, at least in terms of utilization. State oil company Petrobras continuously announces new discoveries offshore, most. In deepwater areas, and plans to move northward up its coast to explore several other deepwater areas.
India is perhaps the second brightest area. Although offshore rig utilization is higher than in Brazil, the difficulty and amount of time required to work with ONGC make this market
somewhat less attractive. However, ONGC is making an effort to attract foreign operators to its shore and is offering 27 blocks in its third concession round. Only seven companies have submitted bids, however
EFFECTS ON THE ENVIRONMENT
Offshore oil production involves environmental risks, most notably oil spills from oil tankers or pipelines transporting oil from the platform to onshore facilities, and from leaks and accidents on the platform. Produced water is also generated, which is excess water from oil or gas production and includes varying amounts of oil, or other chemicals used in, or resulting from, oil production. According to the organization Culture Change, a Gulf of Mexico rig dumps about 90,000 tons of drilling fluid and cuttings over its lifetime, with its wells also contributing with heavy metals.
CONCLUSION
Offshore oil and gas production is more challenging than land-based installations due to the remote and harsher environment. Much of the innovation in the offshore petroleum sector concerns overcoming these challenges, including the need to provide very large production facilities.
offshore drilling.docx (Size: 682.53 KB / Downloads: 44)
INTRODUCTION
Oil and natural gas are brought to the surface from underground reservoirs through wells that have been drilled and completed to produce these fluids safely and economically. Fundamental technology of drilling, completion and production of oil and gas is common to onshore and offshore areas. But environmental conditions of a field affect facilities and engineering works of the field. Offshore areas produced 20-30 % of the oil and gas supply. Oil and natural gas accounted for about 65% of the world energy supply.
OFFSHORE DRILLING.
Offshore drilling refers to a mechanical process where a wellbore is drilled through the seabed. It is typically carried out in order to explore for and subsequently produce hydrocarbons which lie in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the continental shelf, though the term can also be applied to drilling in lakes, inshore waters and inland seas.
Drilling offshore, in some instances hundreds of miles away from the nearest landmass, poses a number of different challenges over drilling onshore. The actual drilling mechanism used to drill into the sea floor is much the same as can be found on an onshore rig. However, with drilling at sea, the sea floor can sometimes be thousands of feet below sea level. The earlier offshore drilling was limited to coastal oil deposits that were accessible from piers, but oil companies today can choose from a variety of elaborate methods, letting them drill almost anywhere at almost any depth. Since the land that is going to be drilled cannot provide a base for offshore drilling as it does for onshore drilling, an artificial platform must be created. This artificial platform can take many forms, depending on the characteristics of the well to be drilled, including how far underwater the drilling target is. Oil-drilling technology is constantly improving, and some rigs combine elements from different models to achieve specific abilities.
DIRECTIONAL AND HORIZONTAL DRILLING
Directional drilling is an exciting extraction technique in onshore and offshore drilling in that previously inaccessible reservoirs, long and thin reservoirs and reservoirs under shallow lakes can be reached after drilling at least 2,000 feet into the ground. With just one rig, 20 or more wells can be drilled, making it an economically productive technique.
Horizontal drilling, unlike directional drilling, can make a 90-degree turn after drilling only a few feet into the ground. Among the three main types of horizontal wells (short, medium and long radius), long radius is a good choice for offshore drilling, as these wells can have curvature radii of 1,000 to 4,500 feet with horizontal extension capability of 15,000 feet. A single drilling in the middle of a remote expanse of water can therefore be quite effective and practicable.
ROTARY DRILLING
Another dual-purpose, onshore and offshore drilling method is rotary drilling, or use of a rotating drill bit to dig into the earth. Rotary drilling consists of four key types of equipment: prime movers, hoisting equipment, rotating equipment and circulating equipment.
Prime movers give power to all the other pieces of equipment, whether through diesel or natural gas engines or turbines. Hoisting equipment helps lift and lower the rotating equipment in the event those parts need to be replaced. The rotating equipment, consisting of a drillpipe, the drill bit and drill collars, does the actual drilling. Circulating equipment is needed to cool down and lubricate the drill bit, remove debris, control pressure and slather the machinery with "mud," or drilling fluid. A blowout preventer located underneath the rig also helps seal the well in the event that the drilling fluid is unable to control any surges of upward pressure emanating from the oil and gas below.
TYPES OF OFFSHORE OIL RIG
The earliest offshore drilling was limited to coastal oil deposits that were accessible from piers, but oil companies today can choose from a variety of elaborate methods, letting them drill almost anywhere at almost any depth. From roving, computer-controlled contraptions to giant "spar" platforms held up by 10,000-foot poles, today's deepwater rigs are going far beyond anything their offshore forefathers could have imagined.
HISTORY
Around 1896, the first submerged oil wells in salt water were drilled in the portion of the Summerland field extending under the Santa Barbara Channel in California. The wells were drilled from piers extending from land out into the channel.
Other notable early submerged drilling activities occurred on the Canadian side of Lake Erie in the 1900s and Caddo Lake in Louisiana in the 1910s. Shortly thereafter wells were drilled in tidal zones along the Texas and Louisiana gulf coast. The Goose Creek Oil Field near Baytown, Texas is one such example. In the 1920s drilling activities occurred from concrete platforms in Venezuela’s Lake Maracaibo.
One of the oldest subsea wells is the Bibi Eibat well, which came on stream in 1923 in Azerbaijan.[3][dubious – discuss] The well was located on an artificial island in a shallow portion of the Caspian Sea. In the early 1930s, the Texas Co., later Texaco (now Chevron) developed the first mobile steel barges for drilling in the brackish coastal areas of the Gulf of Mexico.
OFFSHORE DRILLING SCENARIO IN INDIA
Brazil continues to be the brightest spot in the worldwide rig market, at least in terms of utilization. State oil company Petrobras continuously announces new discoveries offshore, most. In deepwater areas, and plans to move northward up its coast to explore several other deepwater areas.
India is perhaps the second brightest area. Although offshore rig utilization is higher than in Brazil, the difficulty and amount of time required to work with ONGC make this market
somewhat less attractive. However, ONGC is making an effort to attract foreign operators to its shore and is offering 27 blocks in its third concession round. Only seven companies have submitted bids, however
EFFECTS ON THE ENVIRONMENT
Offshore oil production involves environmental risks, most notably oil spills from oil tankers or pipelines transporting oil from the platform to onshore facilities, and from leaks and accidents on the platform. Produced water is also generated, which is excess water from oil or gas production and includes varying amounts of oil, or other chemicals used in, or resulting from, oil production. According to the organization Culture Change, a Gulf of Mexico rig dumps about 90,000 tons of drilling fluid and cuttings over its lifetime, with its wells also contributing with heavy metals.
CONCLUSION
Offshore oil and gas production is more challenging than land-based installations due to the remote and harsher environment. Much of the innovation in the offshore petroleum sector concerns overcoming these challenges, including the need to provide very large production facilities.