Two step-change technologies are paving the way for drilling's future

In the future, drilling rigs will be spudding wells in fields that are considered impossible today due to technology limitations. Such fields may be too deep, too hot, too depleted, too expensive, too remote, or in waters that are too deep or too environmentally sensitive.

The low-hanging fruit has been picked already, and operators, service companies and drilling contractors are working hard on innovations to overcome these technical obstacles to bring hydrocarbons to the thirsty market.

Two of the most exciting new technologies that will have a big impact in the near future are MonoDiameter drilling with expandable tubulars, and casing drilling.

MonoDiameter concept tested

Solid expandable tubulars are going to save the drilling industry a lot of money. With a MonoDiameter well, an operator can replace a traditional casing string, which telescopes from 36 in. diameter at the surface to 51/2 in. at the bottom, with an expandable casing string that is 95/8 in. diameter from top to bottom, using only half the steel. In addition to being able to drill such a well with a US $60,000/day, third-generation rig instead of a $200,000/day, sixth-generation rig, big savings will come from downsizing the riser and the blowout preventer (BOP) stack. While conventional offshore drilling schemes require an average of 2,800 bbl of mud and cement, MonoDiameter wells would only need about 945 bbl. Cuttings volumes would be reduced from 1,450 bbl to only 440 bbl for an average deepwater well using this new technology, so there is less impact on the environment. The larger casing at the bottom of the well enables increased production capacity and better fracturing jobs and allows operators to install intelligent well equipment at any depth.

Shell successfully tested Enventure's MonoDiameter wellbore system at the Thomas-Rife Gas Unit No. 15 well in Starr County, south Texas. The proof-of-concept well blazed the trail for the first offshore MonoDiameter technology application in the Gulf of Mexico, probably in the fourth quarter of 2003. Shell has three potential sites already lined up for the offshore test, said Raoul Restucci, chairman and chief executive officer of Shell E&P Company.

MonoDiameter wells will likely be commonplace in 5 years, he said, because they can guarantee a well will reach total depth, no matter how hard the rock is or what the fracture gradient may be. Instead of subsea completions, operators will be able to drill extended reach wells from nearby platforms or even from shore without any drag problems. "We'll be able to drill 20-mile extended-reach wells 5 years from now. This is more of a step change than horizontal drilling," Restucci said. He predicts that the industry's uptake of this new expandable technology will be five times faster than horizontal drilling because engineers understand the robustness of the equipment better.

"We fully expect the technology to be ready to take offshore by the fourth quarter of 2003," said Lance Cook, president and chief executive officer of Enventure Global Technology, the joint venture of Shell and Halliburton to commercialize the MonoDiameter technology.

Restucci said he's actually more excited about applications for this technology in the Rocky Mountains than offshore applications. MonoDiameter wells can significantly change the economics of deep wells tapping tight gas sands that generally require massive fracture treatments in order to produce economically.

"I believe this will literally change the way we do business around the well bore," said John Darley, director of Shell Technology E&P.

Enventure has opened offices in Houston, Lafayette, Dubai, Malaysia, Scotland and Nigeria in preparation.

Casing drilling cuts time by 30%

By eliminating the need for drillpipe, casing drilling allows operators to drill, case and evaluate oil and gas wells simultaneously with no tripping of pipe. The well is drilled using standard oilfield casing that remains in the hole at all times, preserving well integrity. Drill bits and other downhole tools are lowered via wireline inside the casing and latched to the last joint of casing. Smaller wellbore diameters will mean lower mud and cementing costs. Tremendous cost savings can be had in swelling and sloughing formations, and there will be fewer washouts.

With casing drilling, there will be no more:

• reaming;
• taking a kick while tripping the drill string;
• hole problems caused by swab and surge pressures; or
• key seats and wearing holes in previously set casing.

Although Tesco has a specially designed casing drilling rig with its split crown block and traveling block, wireline BOP integrated in the top drive and special casing handling equipment, almost any drilling rig can be adapted to use casing drilling technology.

Tesco was successful in applying its casing drilling technology recently on an unmodified drilling rig in South Texas. A 41/2-in. casing string with buttress profile connections was drilled (rotated) from about 6,700 ft to 10,000 ft (2,044 m to 3,050 m), successfully passing through a severely depleted zone and through numerous zones normally associated with severe lost circulation. By successfully drilling through these problem zones using casing drilling technology, the operator was able to eliminate the need for a previously planned intermediate casing string, saving about 20% of the total well AFE cost. Average well AFEs for that area had been previously budgeted at US $1 million.

This success represents the first time that Tesco's proprietary casing drilling products have been used on a conventional land rig to drill with casing, paving the way for this technology to be commercialized on conventional rigs around the world.

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