Jun. 24, 2024
Offshore drilling began in , just 38 years after Col. Edwin Drake drilled the first well in . H.L. Williams is credited with drilling a well off a wooden pier in the Santa Barbara Channel in California. He used the pier to support a land rig next to an existing field. Five years later, there were 150 'offshore' wells in the area. By , steel piers were being used in Rincon and Elwood (California) to support land-type drilling rigs. In , a steel-pier island (60 × 90 ft with a 25-ft air gap) was built ½ mile offshore by a small oil company, Indian Petroleum Corp., to support another onshore-type rig. Although the wells were disappointing and the island was destroyed in by a storm, it was the forerunner of the steel-jacketed platforms of today.[1]
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Overview
In , a field was discovered offshore Texas. Subsequently, a 9,000-ft well was drilled in in fashion similar to the California wells by use of a wooden pier. With the start of World War II, however, all offshore drilling activities halted. After the end of World War II, the state of Louisiana held an offshore state waters lease sale in . This was followed in by the state of California (Cunningham-Shell Act) lease sale, which allowed exploration of oil and gas sands.[1] Before the latter act, core drilling could be done only until a show of oil and gas. At that time, all drilling had to stop and the core hole plugged with cement.
The first on-water drilling
The first 'on-water drilling' was born in the swamps of Louisiana in the early s with the use of shallow-draft barges. These barges were rectangular with a narrow slot in the aft end of the barge for the well conductor. Canals were, and still are, dredged so that tugs can mobilize the barges to locations. Later, barges were 'posted' on a lattice steel structure above the barge, allowing them to work in deeper water depths by submerging the barge on the bay bottoms. These barges usually required pilings around them to keep them from being moved off location by winds and waves. The first 'offshore' well, defined as, 'out of sight of land,' was started on 9 September, by a tender assist drilling (TAD) unit owned by Kerr-McGee in 15 ft of water in the Gulf of Mexico (GOM). An ex-World War II 260 × 48-ft barge serviced the drilling equipment set (DES), which consisted of the drawworks, derrick, and hoisting equipment located on a wooden pile platform.[2]
The Breton Rig 20 (Fig. 1), designed by John T. Hayward(who was with Barnsdall Refining Co. at the time), was a large 'posted' submersible barge credited in with drilling some of the first wells in the open waters of Louisiana. It was different from the Kerr-McGee barge in that all the drilling equipment was on one barge, and it could be towed as a complete unit. The unit, which was a conversion from an inland drilling barge, had two stability pontoons, one on each side of the barge, that hydraulically jacked up and down as the barge was submerged and pumped out. These pontoons provided the necessary stability for this operation. The Breton Rig 20, later known as the Transworld Rig 40, was a major step forward because it eliminated the cost and time required to build a wooden platform to support all or some of the offshore-type rig. Although it drilled only in predominantly protected bays in shallow water (less than 20 ft), the Breton Rig 20 may be able to lay a qualified claim as being the first mobile offshore drilling unit (MODU).[3][4]
Fig. 1'Breton Rig 20, a converted 'posted' swamp drilling barge capable of drilling in open Louisiana water depths up to 20 ft in . Retired in .
The first MODU
The first truly offshore MODU was the Mr. Charlie, designed and constructed from scratch by Ocean Drilling and Exploration Co. (ODECO), headed by its inventor and president, 'Doc' Alden J. Laborde. The Mr. Charlie (Fig. 2) was a purpose-built submersible barge built specifically to float on its lower hull to location and, in a sequence of flooding the stern down, ended up resting on the bottom to begin drilling operations. When the Mr. Charlie went to its first location in June , Life magazine wrote about the novel new idea to explore for oil and gas offshore.[5] The Mr. Charlie , rated for 40-ft water depth, set the tone for how most MODUs were built in the Gulf of Mexico (GOM). Usually, an inventor secured investors, in this case Murphy Oil, and then found a customer with a contract to drill for, in this case Shell Oil, allowing bank loans to be obtained to build the unit.
Fig. 2'Mr. Charlie, the first purpose-built (June ) open-water MODU rated for 40-ft water depth. Retired in late and now a museum and training rig in Morgan City, Louisiana.
Because the shelf dropped off quickly, and water depths increased rapidly off the shore of California, the approach there was entirely different from that in the GOM. Rigs were installed on surplus World War II ship hulls modified to drill in a floating position compared with sitting a submersible barge on the ocean bottom, as done in the GOM. Oil companies formed partnerships or proceeded independently, but MODUs were not designed and constructed by contract drilling companies in California. All design and construction was done in a highly secretive manner with little sharing of knowledge, because technology was thought to give an edge in bidding for state oil and gas leases. Before the leasing of oil and gas rights in , oil companies cored with small rigs cantilevered over the side midship of old World War II barges. These barges did not have well-control equipment or the ability to run a casing program. They could only drill to a designated core depth with the understanding that if they drilled into any oil and/or gas sands, they would stop, set a cement plug, and pull out of the core hole. These core vessels were highly susceptible to wave action, resulting in significant roll, heave, and pitch, which made them difficult to operate.
The first offshore drilling unit to implement subsea well control
With leasing from the state of California to explore and produce oil and gas, well control and the ability to run multiple strings of casing became mandatory and required a totally new, unproven technology. The first floating drilling rig to use subsea well control was the Western Explorer (Fig. 3) owned by Chevron, which spudded its first well in in the Santa Barbara Channel. Others followed quickly, with all of them concerned about the marine environment and technology to allow drilling in rough weather. In , the CUSS 1 was built from another World War II barge. The unit, built by the CUSS group (Continental, Union, Shell, and Superior Oil), was 260 ft long and had a 48-ft beam. The CUSS group eventually evolved into what is now Global Santa Fe.
Fig. 3'Western Explorer, the first () floating oil- and gas-drilling MODU that used subsea well control. Retired in .
The original designers had no examples or experiences to go by, so novelty and innovation were the course of the day:
It was an exciting and amazing time, considering that everyone was starting with a blank sheet of paper.
Fig. 4 shows the Humble SM-1 drilling barge (204 × 34 × 13 ft) built and owned by Humble Oil and Refining Co. (now ExxonMobil) in . Fig. 5 shows the subsea equipment used to drill the wells. Note that it has no marine riser. The Humble SM-1 drilled 65 wells for a total cost of $11.74/ft, about double the cost of land drilling at the time, in an average water depth of 159 ft and with a maximum well depth of 5,000 ft. The unit averaged 8.93 days per well and drilled an average of 324 ft/D. Unfortunately, the unit sank in a storm in while on loan to another operator.[6] At the insistence of insurance underwriters, the American Bureau of Shipping (ABS) wrote and implemented, in , the first independent codes, guidelines, and regulations concerning the design, construction, and inspections of MODU hulls.
Fig. 4'Humble SM-1, a floating MODU designed and operated by Humble Oil & Refining Co. (now ExxonMobil) in . One of a number of 'top secret' drilling units of the mid s. Courtesy of Exxon- Mobil Development Co.
Fig. 5'Humble Oil and Refining Co.'s Humble SM-1 subsea drilling system used offshore California. Courtesy ExxonMobil Development Co.
Offshore drilling unit design evolution
With the Mr. Charlie (bottom founded) and Western Explorer (floating) as the first MODUs, another concept for a MODU showed up in the form of a 'jackup'. This type of unit floated to location on a hull with multiple legs sticking out under the hull. Once on location, the legs were electrically or hydraulically jacked down to the ocean bottom, and then the hull was jacked up out of the water. With this approach, a stable platform was available from which to drill. In World War II, the De Long spud can jacks were installed on barges for construction and/or docks. The De Long-type rigs (Fig. 6) shows an example, the Gus I) were the first jackups built in .[7] Although jackups initially were designed with 6 to 8 legs and then a few with 4 legs, the vast majority of units today have 3 legs. The Gus I was constructed with independent legs. The Le Tourneau Co. built for Zapata Corp. the first lattice-leg jackup, the Scorpion (Fig. 7), which had independent legs with spud cans. To this day, Le Tourneau continues to specialize in lattice-leg-type jackup MODUs.
Fig. 6'With a De Long-type jacking system, the Gus I, built in and rated for 100-ft water depth, was the forerunner of the modern jackup. Initially, two barges that were eventually joined permanently, but the unit was lost in a storm.
Fig. 7'Le Tourneau's Scorpion built for Zapata (now Diamond Offshore Drilling Inc.) in for 80-ft water depth as an independent-leg jackup. Lost in .
A major evolution for the jackup design was the introduction of the cantilevered drill-floor substructure (Fig. 8) in the late s and early s. As fixed platforms got bigger, the slot jackups could not 'swallow' or surround the platform with its slot containing the drilling equipment; however, the cantilever units could skid the cantilever out over the platform after jacking up next to it. Before the cantilevered substructure, all jackups had slots, usually 50 ft. square, located in the aft end of the hull. During tows, the substructure was skidded to the metacenter of the hull, but during drilling operations, the substructure was skidded aft over the slot. The derrick and/or crown could be skidded port/starboard to reach wells off center just like today's units do.
In the late s, 'premium' or 'enhanced' jackups were designed and built:
Fig. 8'Le Tourneau's 116C cantilevered jackup with drill floor cantilevered over a fixed platform. Today's workhorse design of jackups. Courtesy Le Tourneau, Inc.
The tender assist drilling (TAD) unit
The TAD concept was used to drill the first offshore 'out of sight of land' well in the world. Initially used as an exploration method, it has evolved into a development tool. The first tenders were shaped like barges, but some are now shaped like ships for better mobilization speeds.
Basically, the DES (Drilling Equipment Set) consists of the derrick, hoisting equipment, BOPs, and some mud-cleaning equipment, reducing the required space and weight to be placed on the fixed platform. The rest of the rig is located on the tender hull moored next to the fixed platform, including:
This approach turned out to be a very cost-effective way to drill from small fixed platforms. Unfortunately, in mild and especially severe weather, the mooring lines could fail, with the hull floating away, as it often did in a GOM 'norther.' Today, most TADs operate in benign or calm environments in the Far East and West Africa.
The semisubmersible unit
In , the first semisubmersible (semi) Seahawk TAD (Fig. 9) was converted from an old semi MODU. The semi hull offers superior station keeping and vessel motions compared with ship or barge-shaped hulls:
TADs are seeing new use on deepwater production platforms, such as spars, tension leg platforms (TLPs), and deepwater fixed platforms, which operate beyond jackup water depths.
Fig. 9'World's first purpose-built (conversion) semi TAD unit Seahawk. Converted in from a semi MODU. Courtesy Atwood Oceanics.
Growth of offshore drilling units
Things were off and running in the s, with numerous operators getting into the rig ownership and operation business and new drilling contractors being formed every year. In the early s, Shell Oil saw the need to have a more motion-free floating drilling platform in the deeper, stormier waters of the GOM. Shell noticed that submersibles like the Mr. Charlie, now numbering almost 30 units, were very motion free afloat compared with monohulls. The idea was to put anchors on a submersible, use some of the California technology for subsea equipment, and convert a submersible to what is now known as a semisubmersible or semi. Thus, in , the submersible Bluewater I (Fig. 10) was converted to a semi amid much technological secrecy. In fact, in the mid-s, Shell Oil offered the industry the technology in a school priced at U.S. $100,000 per participant and had lots of takers.
Fig. 10'World's first semi MODU, Bluewater No.1, converted in / by Shell Oil from a submersible hull. Lost in .
Then came the Ocean Driller, the first semi built from the keel up (Fig. 11). The Ocean Driller, designed and owned by ODECO, went to work for Texaco in , with the mooring and subsea equipment owned by the operator, as was common in the s. The unit was designed for approximately 300 ft. of water depth, with the model tests of the hull done in Doc Laborde's swimming pool. The Ocean Driller could also sit on bottom and act as a submersible, which it did well into the s.
Fig. 11'World's first purpose-built () semi MODU, Ocean Driller. Unit could operate as a semi or submersible. Retired in and scrapped. Courtesy ODECO (now Diamond Offshore Inc.).
First generaltion semi units
Most of the first-generation units could sit on bottom or drill from the floating position as a hedge against unemployment. The shape and size of the first semis varied widely as designers strived to optimize vessel motion characteristics, rig layout, structural characteristics, VDL, and other considerations. The 'generation' designation of semis is a very loose combination of when the unit was built or significantly upgraded, the water depth rating, and the general overall drilling capability.
Newer generation semi units
In the early s, a new, second-generation semi was designed and built with newer, more sophisticated mooring and subsea equipment. This design generally was designed for 600-ft water depth, with some extending to greater than 1,000 ft. The Ocean Victory class (Fig. 12) was typical of the units of this era, which concentrated heavily on reducing motions of the platform compared with increased upper-deck VDL rating. Many were built, and, in the middle to late s, a number of third-generation semis were designed and built that could moor and operate in greater than 3,000 ft of water depth and more severe environments. Many of the third-generation units were upgraded in the s to even deeper water depth ratings with more capabilities and became fourth-generation units. With a few exceptions, the operating displacement of these units went from '18,000 long tons in the s to more than 40,000 long tons in the s.
Fig. 12'ODECO's multicolumn second-generation semi Ocean Victory class of early s. Unit shown is the Ocean Voyager, drilling in the North Sea in the early s. This design proved structurally very attractive for upgrade to fourth- and fifth-generation units (see Fig. 14.14).
In the late s, the fifth-generation units, such as the Deepwater Nautilus shown in Fig.13, became even larger (> 50,000-long-ton displacement) and more capable. These units can operate in extremely harsh environments and in greater than 5,000-ft water depth. Some second- and third-generation semis have been converted, given life extensions to their hulls and upgrades to their drilling equipment so as to be classed as fourth-generation units. Fig. 14 shows a second-generation Ocean Victory class unit (see Fig. 12 ) that was completely upgraded to a fifth-generation unit capable of mooring and operating in 7,000-ft water depth. Note the addition of column 'blisters' for increased VDL, ' 50% increase in deck space, and the addition of riser storage and handling. A limited number of third-, fourth-, and fifth-generation semis have dynamic positioning (DP) assist or full-DP station keeping compared with a spread-mooring system.
Fig. 13'Deepwater Nautilus, one of the newly built fifth-generation ultradeepwater semis that has DP assist for its spread-mooring system. Note spread columns for increased VDL and stability. Courtesy Transocean Inc.
Fig. 14'Ocean Baroness, one of the Ocean Victory class (Fig. 12) second-generation semis upgraded to a fifth-generation unit. Note blister additions to column, deck expansion, and much larger derrick. This semi also did surface BOP work in Malaysia in , along with setting the world's record self contained spread-mooring water depth (6,152 ft). Courtesy Diamond Offshore Drilling Inc.
The fixed platform units
Fifty years ago, fixed platforms had land rigs placed on them to drill and complete wells. Today's platform rigs have been repackaged so that they:
Drilling platform rigs are still common, but today's units look far different from those of 30 or 40 years ago. Conventional platform rigs are usually loaded out with a derrick barge. Some large platforms may have two drilling units on them.
To eliminate the costly derrick barge, 'self-erecting' modular rigs have been built for light workovers and for drilling to moderate depths. Larger units that have the capability of a 1-million-lbm hook load have been built that are lightweight, easier to rig up/load out, and self-erecting. The advent of spars and TLPs in deep water, where space and deck load are critical, has generated even a more sophisticated modular deepwater platform rig, which is highly specialized to the structure on which it sits (Fig. 15). These platform rigs:
Fig. 15'Example of highly specialized and site-specific modular fixed-platform rigs used on spars, deepwater fixed platforms, and TLPs. This unit is on a TLP in the GOM. Courtesy Helmerich & Payne Intl. Drilling Co.
By the mid-s, the jackup-designed rigs were displacing submersibles in increasing numbers. Jackups had more water depth capability than even the largest submersibles (some could operate in 175-ft water depth),[7] and they did not slide off location in severe weather. From this point on, jackup and semi designs were refined and made larger and more capable from a drilling and environmental standpoint.
The ship and barge shaped units
Ship and barge-shaped floating MODUs, initially attractive because of their transit speed and ease in mobilizations, decreased in number as semis and jackups became more popular. One exception was the DP drillship, which held location over the wellbore by use of thrusters and main screw propulsion rather than a spread-mooring system.
Dual drilling consists basically of some degree of two complete derricks and drilling systems on one hull, so that simultaneous operations, such as running casing while drilling with the other derrick, can be performed. These units are very expensive to build and operate, but can overcome their cost with supposedly higher efficiency. They should be reviewed for possible use, under the right conditions, as an alternative to standard single-operation units. Examples of such conditions include:
Technological development of the MODU
The offshore drilling industry has had spurts of construction and design improvements over its 50-year history. The first was the conception of the MODUs in the mid-s, followed by a mild building period in the mid-s. In the early s, there were significant numbers of jackups and semisubmersibles built. However, the major boom of the late s and early s has been unmatched in numbers of rigs built. Starting in the late s, a number of drilling contractors upgraded rigs built in the s and early s to deepwater depths, more severe environmental ratings, and better drilling abilities rather than building new units. The concept was that delivery and cost could be cut in half compared with a new build. Some drilling contractors have successfully built their entire business plan around conversion instead of new build.
Since the oil and gas bust of the mid-s, there has only been one spurt of new building, and that was in the late s. Mergers and buyouts of drilling contractors and rigs dominated the industry from the mid-s to the mid-s. One drilling contractor, Global Santa Fe, monthly publishes a percentage number related to day rate and cost of building a new unit. A 100% rating means new units can be built profitably; however, the percentage number has lingered in the 40 to 60% range over the last 15 years or so, with spurts into 80%. By its nature, the drilling business is built on optimism for the future that may not always show proper returns on investment in terms of new builds or conversions. High on hope and the future, the contract drilling business has historically not been conservative and has not followed generally accepted rules of investment.
In the early s, the average age of the fleet was more than 20 years, with some units more than 30 years old. Few are less than 5 years old. Some have been upgraded and have had life extensions, which means that, with good care and maintenance, the basic hull, if it and/or the rig are not rendered technologically obsolete, may last more than 40 years, as do units in the dredging business.
'Technologically obsolete' means that the unit needs to have:
1. Up-to-date features such as:
2. Enough power to run all the new equipment
The fleet in stood at approximately 390 jackups, 170 semis, 30 ships, and 7 submersibles. Fixed-platform rigs number about 50, and TADs number about 25.
The future of offshore drilling
The consensus is that the offshore drilling business will continue to grow, with emphasis on technical breakthroughs to reduce drilling costs. The industry has demonstrated that it can drill in water depths up to and more than 10,000 ft., and can operate in the most severe environments, but all at a very high cost that can run into hundreds of thousands of dollars per day. Ultra deepwater wells costing more than $50 million are common, and some wells have cost more than $100 million. It is very difficult to justify wells that cost this much given the risks involved in drilling the unknown. The challenge to the offshore industry is to drill safely and economically, which means 'technology of economics,' with safety, environment, security, and personnel health all playing a large role.
References
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Suggested reading:Silcox, W.H., et al. . Offshore Operations. In Petroleum Engineering Handbook, second edition. Richardson, Texas: SPE, Chapter 18.
Barnes, K.B., and McCaslin, L.S. Jr. . Gulf of Mexico Discovery. Oil & Gas J 47 (March 18): 96.
Mobile Rig Register, eighth edition. . Houston, Texas: ODS-Petrodata.
Howe, R.J. . The Evolution of Offshore Mobile Drilling Units. Drilling and Production Practice. API-66-120.
Laborde, A.J. . My Life and Times. New Orleans, Louisiana: Laborde Print Company.
Harris, L.M. . Humble SM-1 Offshore Exploration Vessel, Petroleum Engineering Project Report. Los Angeles, California: Humble Oil and Refining Co., Production Department California Area.
Howe, R.J. . Evolution of Offshore Drilling and Production Technology. Presented at the Offshore Technology Conference, Houston, Texas, 5-8 May. OTC--MS. http://dx.doi.org/10./-MS
See also
PEH:Offshore_Drilling_Units
Tender assist drilling (TAD) units
Semisubmersibles
Noteworthy papers in OnePetro
T. F. Marucci and D. E. McDaniel . Safety of Mobile Offshore Drilling Units, Offshore Technology Conference, 22-24 April. -MS. http://dx.doi.org/10./-MS
American Bureau of Shipping (ABS)
This article is about onshore equipment for boring holes into the ground. For offshore oil rig, see Oil platform . For drilling tunnels, see Tunnel boring machine . For handheld drilling tool, see Drill
Drilling the Bakken Formation in the Williston Basin Large hole drilling rig for blast-hole drillingA drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person and such are called augers. Drilling rigs can sample subsurface mineral deposits, test rock, soil and groundwater physical properties, and also can be used to install sub-surface fabrications, such as underground utilities, instrumentation, tunnels or wells. Drilling rigs can be mobile equipment mounted on trucks, tracks or trailers, or more permanent land or marine-based structures (such as oil platforms, commonly called 'offshore oil rigs' even if they don't contain a drilling rig). The term "rig" therefore generally refers to the complex equipment that is used to penetrate the surface of the Earth's crust.
Small to medium-sized drilling rigs are mobile, such as those used in mineral exploration drilling, blast-hole, water wells and environmental investigations. Larger rigs are capable of drilling through thousands of metres of the Earth's crust, using large "mud pumps" to circulate drilling fluid (slurry) through the drill bit and up the casing annulus, for cooling and removing the "cuttings" while a well is drilled. Hoists in the rig, a derrick, can lift hundreds of tons of pipe. Other equipment can force acid or sand into reservoirs to facilitate extraction of the oil or natural gas; and in remote locations there can be permanent living accommodation and catering for crews (which may be more than a hundred). Marine rigs may operate thousands of miles distant from the supply base with infrequent crew rotation or cycle.
History
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Antique drilling rig now on display at Western History Museum in Lingle, Wyoming. It was used to drill many water wells in that area'many of those wells are still in use. Antique drilling rigs in Zigong, ChinaUntil internal combustion engines were developed in the late 19th century, the main method for drilling rock was muscle power of man or animal. The technique of oil drilling through percussion or rotary drilling has its origins dating back to the ancient Chinese Han dynasty in 100 BC, where percussion drilling was used to extract natural gas in the Sichuan province.[1] Early oil and gas drilling methods were seemingly primitive as it required several technical skills.[1][2] The skills involved the availability of heavy iron bits and long bamboo poles, the manufacturing of long and sturdy cables woven from bamboo fiber, and levers. Heavy iron bits were attached to long bamboo cables suspended from bamboo derricks and then were repeatedly raised and dropped into a manually dug hole by having two to six men jumping on a lever.[1] Han dynasty oil wells made by percussion drilling was effective but only reached 10 meters deep and 100 meters by the 10th century.[1] By the 16th century, the Chinese were exploring and drilling oil wells more than 2,000 feet (610 m) deep.[2] Chinese well drilling technology was introduced to Europe in .[3] A modernized variant of the ancient Chinese drilling technique was used by American businessman Edwin Drake to drill Pennsylvania's first oil well in using small steam engines to power the drilling process rather than by human muscle.[1] Cable tool drilling was developed in ancient China and was used for drilling brine wells. The salt domes also held natural gas, which some wells produced and which was used for evaporation of the brine. Drake learned of cable tool drilling from Chinese laborers in the U.S.[4] The first primary product was kerosene for lamps and heaters.[5][6] Similar developments around Baku fed the European market.
In the s, outside of the oil and gas industry, roller bits using mud circulation were replaced by the first pneumatic reciprocating piston Reverse Circulation (RC) drills, and became essentially obsolete for most shallow drilling, and are now only used in certain situations where rocks preclude other methods. RC drilling proved much faster and more efficient, and continues to improve with better metallurgy, deriving harder, more durable bits, and compressors delivering higher air pressures at higher volumes, enabling deeper and faster penetration. Diamond drilling has remained essentially unchanged since its inception.
Petroleum drilling industry
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Oil rigs operational
Natural gas rigs operational
Oil and natural gas drilling rigs are used not only to identify geologic reservoirs, but also used to create holes that allow the extraction of oil or natural gas from those reservoirs. Primarily in onshore oil and gas fields once a well has been drilled, the drilling rig will be moved off of the well and a service rig (a smaller rig) that is purpose-built for completions will be moved on to the well to get the well on line.[7] This frees up the drilling rig to drill another hole and streamlines the operation as well as allowing for specialization of certain services, i.e. completions vs. drilling.
Mining drilling industry
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Mining drilling rigs are used for two main purposes, exploration drilling which aims to identify the location and quality of a mineral, and production drilling, used in the production-cycle for mining. Drilling rigs used for rock blasting for surface mines vary in size dependent on the size of the hole desired, and is typically classified into smaller pre-split and larger production holes. Underground mining (hard rock) uses a variety of drill rigs dependent on the desired purpose, such as production, bolting, cabling, and tunnelling.
Mobile drilling rigs
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Mobile drilling rig mounted on a truckIn early oil exploration, drilling rigs were semi-permanent in nature and the derricks were often built on site and left in place after the completion of the well. In more recent times drilling rigs are expensive custom-built machines that can be moved from well to well. Some light duty drilling rigs are like a mobile crane and are more usually used to drill water wells. Larger land rigs must be broken apart into sections and loads to move to a new place, a process which can often take weeks.
Small mobile drilling rigs are also used to drill or bore piles. Rigs can range from 100 short tons (91,000 kg) continuous flight auger (CFA) rigs to small air powered rigs used to drill holes in quarries, etc. These rigs use the same technology and equipment as the oil drilling rigs, just on a smaller scale.
The drilling mechanisms outlined below differ mechanically in terms of the machinery used, but also in terms of the method by which drill cuttings are removed from the cutting face of the drill and returned to surface.
Automated drill rig
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An automated drill rig (ADR) is an automated full-sized walking land-based drill rig that drills long lateral sections in horizontal wells for the oil and gas industry.[8] ADRs are agile rigs that can move from pad to pad to new well sites faster than other full-sized drilling rigs. Each rig costs about $25 million. ADR is used extensively in the Athabasca oil sands. According to the "Oil Patch Daily News", "Each rig will generate 50,000 man-hours of work during the construction phase and upon completion, each operating rig will directly and indirectly employ more than 100 workers." Compared to conventional drilling rigs", Ensign, an international oilfield services contractor based in Calgary, Alberta, that makes ADRs claims that they are "safer to operate, have "enhanced controls intelligence," "reduced environmental footprint, quick mobility and advanced communications between field and office."[8] In June the first specifically designed slant automated drilling rig (ADR), Ensign Rig No. 118, for steam assisted gravity drainage (SAGD) applications was mobilized by Deer Creek Energy Limited, a Calgary-based oilsands company.[9][10]
Auger drills
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An auger drill is a spiral-shaped tool. Its main function is the drilling of holes in the ground and other materials - or surfaces such as ice, wood, etc. The design of an auger depends on the kind of material it's meant to drill into, hence there are different types of auger drills.[11] Auger drills come in varying sizes and can drill holes up to a depth of 95 ft below the ground. They are known to be quite versatile, saving time and energy during construction work or even personal projects.
Drill buckets
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A drill bucket, or auger bucket, is a drilling head that accumulates spoil inside and can be lifted from the hole periodically to be emptied.[12]
See also
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References
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