April 1999

What's happening in drilling

New mobile land rig package; Expandable-casing prototype trial coming

April 1999 Vol. 220 No. 4 
J. John Grow, 
Engineering Editor 

Taylor made rigs, expandable-casing and CT drilling in the GOM

A sign of the times, how to survive yet another downturn in the "good old" oil patch. No one was ever promised "a bed of roses," but "ouch" this patch is so thorny.

As the norm, we seek out better and more efficient ways to conduct business. Cutting costs does not necessarily have to mean cutting heads — innovation, ingenuity and creativity have made this country great, and our generation is not any less challenged than that of our forefathers.

Multi-component drilling rig packages. Taylor Rigs, Tulsa Port of Catoosa, has sold Marathon Oil, Alaska region, a multi-component drilling rig package which includes a Taylor 950 drilling unit, mobile mud system and substructure. This system is designed for a unique type of gas well drilling being conducted by Marathon in the Kenai Peninsula region. New technology incorporated into the package will make the rig more suited to their specific needs, reducing costs, drilling time and environmental impact, including capabilities to withstand extremely cold temperatures, Fig. 1. Taylor will develop the new rig, scheduled for delivery in mid-summer, in conjunction with Marathon.

Expandable-casing update. Large fields lie under deep water, where projects depend on price expectations 5 to 10 years in advance, not on those of today.

Last summer, Shell Technology Ventures, Inc. and Halliburton Energy Services joined in an equal partnership, Enventure Global Technology, to develop and commercialize expandable-tubular technology, which originated at Shell. The technology has demonstrated its potential to reduce deepwater-drilling costs. See "What’s happening in drilling" World Oil, September 1998.

The joint venture made a breakthrough development in January by successfully expanding the first joint of its solid 13-3/8 ´ 16-in. expandable-casing system, Fig. 2. This latest advancement should make deepwater exploitation more economically feasible for operators. Enventure is readying a prototype system for field trials in mid-May. The company believes that trials will prove the system for contingency applications, such as extending 16-in. casing shoes.

The 13-3/8 ´ 16-in. system is scheduled to be used in October for a deepwater GOM oil exploration well. Fluid losses will not allow the operator to drill to targeted depth with conventional casing. Uncertainties in pore pressure and fracture gradient plots and low margins will require various shoe extensions to reach the targeted depth.

However, the expansion should save the operator as many as three casing strings by extending the 16-in. shoe across a lost circulation zone that typically occurs within 500 to 1,000 ft of drill out. The 13-3/8 ´ 16-in.system expands to about 15-in. OD and 14-1/4-in. ID. Expansion will enable 13-3/8-in. casing to be run to a greater depth than previously possible in deep water.

Besides the 13-3/8 ´ 16-in. system for deepwater well environments, Enventure is readying another prototype for workover field trials in mid-May. The prototype to be field-tested is a 3-1/2 ´ 5-in., short-clad casing system, which can repair an existing wellbore for continued, deeper drilling. The system repairs damaged casing by cladding expandable casing inside of existing tubulars.

Prototype system field trials will be in a gas well drilled in 1970. The hole has high temperatures and possible wellbore obstruction. Expansion of the 3-1/2-in. coiled tubing to an OD almost equal to the existing 5-in. ID casing will give the cladded section about a 3-3/4-in ID, enabling drilling operations through a 3-1/2-in. hole.

First GOM horizontal well drilled and completed successfully with CT. Schlumberger has successfully drilled and completed the first horizontal well in the GOM with CoilDRILL coiled drilling technology. Working in conjunction with the Spirit Energy 76 drilling team, Schlumberger’s Integrated Project Management (IPM) designed, drilled and completed the well.

An exit window was milled through two strings of pipe. About 1,390 ft. of 4-3/4-in. open hole was drilled (750 ft was over 80° inclination). The well was completed by conveying a horizontal completion assembly — consisting of sand control screens, an inflatable packer for zonal isolation and Dowell’s QUANTUM gravel packer open-hole isolation assembly on coiled tubing — to 8,100 ft. This assembly was run and set in one trip, which included cement inflation of the inflatable packer. It is the first GOM well where this completion has been run on coiled tubing; and it was accomplished in a well that is 45 years old. WO

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