When was the first drilling rig?

Offshore drilling began in 1897, just 38 years after Col. Edwin Drake drilled the first well in 1859. 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 1921, steel piers were being used in Rincon and Elwood (California) to support land-type drilling rigs. In 1932, 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 1940 by a storm, it was the forerunner of the steel-jacketed platforms of today.

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Overview

In 1938, a field was discovered offshore Texas. Subsequently, a 9,000-ft well was drilled in 1941 in a fashion similar to the California wells by using 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 1945. This was followed in 1955 by the state of California (Cunningham-Shell Act) lease sale, which allowed exploration of oil and gas sands. 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 1930s 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 1947 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.

The Breton Rig 20 designed by John T. Hayward (who was with Barnsdall Refining Co. at the time), was a large “posted” submersible barge credited in 1949 with drilling some of the first wells in the open waters of Louisiana. It differed 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, 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 lay a qualified claim as being the first mobile offshore drilling unit (MODU).

• Fig. 1—Breton Rig 20, a converted “posted” swamp drilling barge capable of drilling in open Louisiana water depths up to 20 ft in 1949. Retired in 1962.

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 designed to float on its lower hull to location and, through flooding the stern down, rested on the bottom to begin drilling operations. When the Mr. Charlie went to its first location in June 1954, Life magazine wrote about the novel new idea to explore for oil and gas offshore. The Mr. Charlie, rated for a 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 1954) open-water MODU rated for 40-ft water depth. Retired in late 1986 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 provide an edge in bidding for state oil and gas leases. Before the leasing of oil and gas rights in 1955, oil companies cored with small rigs cantilevered over the side midship of old World War II barges. These barges lacked well-control equipment or the capability 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 1955 in the Santa Barbara Channel. Others followed quickly, all concerned about the marine environment and technology to permit drilling in rough weather. In 1956, the CUSS 1 was built from another World War II barge. The unit, constructed by the CUSS group (Continental, Union, Shell, and Superior Oil), was 260 ft long with a 48-ft beam. The CUSS group eventually evolved into what is now Global Santa Fe.

• Fig. 3—Western Explorer, the first (1955) floating oil- and gas-drilling MODU that used subsea well control. Retired in 1972.

The original designers had no examples or experiences to go by, so novelty and innovation were the norm:

• Torque converters on the drawworks were used as heave-motion compensators
• Rotaries were gimbaled to compensate for roll and pitch
• The derrick was placed midship over a hole in the vessel called a "moonpool."
• Blowout preventers (BOPs) were run on casing to the seafloor
• Re-entry into the well was through a funnel above a rotating head (riserless drilling is not new)
• Mud pits were placed in the hull with mud pumps
• Living quarters were added

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 1957. 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 1961 while on loan to another operator. At the insistence of insurance underwriters, the American Bureau of Shipping (ABS) wrote and implemented, in 1968, 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 1957. One of a number of “top secret” drilling units of the mid-1950s. 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 emerged 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. This approach provided a stable platform for drilling. In World War II, the DeLong 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 1954. 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 LeTourneau 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 DeLong-type jacking system, the Gus I, built in 1954 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 1956 for 80-ft water depth as an independent-leg jackup. Lost in 1969.

A major evolution for the jackup design was the introduction of the cantilevered drill-floor substructure (Fig. 8) in the late 1970s and early 1980s. As fixed platforms grew larger, 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.

• The water depth range for most of the early slot and cantilever designs was from 150 to just over 300 ft.
• Cantilever drill-floor centers had a reach of 40 to 45 ft aft of the aft hull transom.
• Variable deck load (VDL) ratings were 3,500 to 5,000 kips.

In the late 1990s, "premium" or "enhanced" jackups were designed and built:

• They could carry much larger deck loads (≥ 7,000 kips)
• They could drill in deeper water depths (≥ 400 ft)
• They had more capable drilling machinery (7,500-psi high-pressure mud systems and 750-ton hoisting equipment)
• They had extended cantilever reach (at least 70 ft.)
• They had larger cantilever load ratings of double or more the earlier units (some > 2,500,000 lbm)

• 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:

• Mud pits
• Mud pumps
• Power generators
• Tubulars and casing storage
• Bulk storage
• Accommodations
• Fuel
• Drill water

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 1992, 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:

• In a semi hull, the wave train can move through the "transparent" hull without exciting it to heave, roll, and pitch, unlike a mono hull
• The lower hull of the semi is below the water at a deeper draft
• The columns offer a reduced area to excite the hull
• The work platform or main deck is above all wave action

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 1992 from a semi MODU. Courtesy Atwood Oceanics.

Growth of Offshore Drilling Units

Things were off and running in the 1950s, with numerous operators getting into the rig ownership and operation business and new drilling contractors being formed every year. In the early 1960s, 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,