'Microhole' coiled tubing drilling holds promise, DOE says

Nick Snow
Washington Correspondent

WASHINGTON, DC, Dec. 13 -- A federally funded technology that could change the way oil and gas wells are drilled was successfully demonstrated in the US Midcontinent, the US Department of Energy said.

A specially designed hybrid "microhole" coiled tubing rig recently drilled 25 test wells to penetrate the Niobrara, a particularly intractable gas formation in western Kansas and eastern Colorado. The effort delivered cost savings of 25-35%/well drilled compared with conventional drilling equipment, DOE's Fossil Energy office said.

It said about 1 tcf of shallow gas that had been bypassed by conventional drilling has become economic as a result. The volume equates to about 5% of the country's annual gas consumption, it indicated.

The commercial Niobrara drilling program—in which 3,000-ft wells were drilled in as little as 19 hr, from rig move-in to move-out—followed a DOE-funded research project undertaken by Gas Technology Institute (GTI) of Des Plaines, Ill. In that effort, GTI partnered with two small firms, Advanced Drilling Technology LLC of Yuma, Colo., and Rosewood Resources Inc. of Dallas, to adapt a conventional coiled tubing rig for drilling exploratory and development wells with ultrasmall diameters.

Normally, coiled tubing rigs are used to service or stimulate production in problematic oil and gas wells, according to DOE. Producers have only recently begun to use them in grassroots exploratory and development areas, largely in Alaska, Canada, and other higher-cost operating areas, it said.

Technology's purpose
GTI's project received funding from DOE's Microhole Technology Initiative. Managed by the Office of Fossil Energy's National Energy Technology Laboratory, the initiative seeks to develop the tools and techniques for drilling ultrasmall boreholes (generally, with diameters of 1-3/4 to 4-1/2 in.) and related downhole microinstrumentation, using coiled tubing drilling rigs that are small and easily transportable.

These rigs—some small enough to mount on a trailer pulled by a standard pickup truck—employ solid tubing coiled around a spool on the trailer to drill boreholes with well casing diameters of less than 4-1/2 in. Such rigs can drill shallow wells very quickly, saving substantially on daily rig costs and dramatically improving the economics of drilling, according to DOE.

GTI's microhole project was meant to pioneer the use of an experimental, "built-for-purpose" coiled tubing rig designed to drill exploratory and development wells with ultrasmall diameters in the Lower 48 states. ADT and its predecessor Coiled Tubing Solutions Inc. designed and fabricated the rig specifically for microhole coiled tubing drilling to depths as great as 5,000 ft. Earlier DOE research had proven this capability to only a few hundred feet, the federal agency said.

GTI and its partners field tested this state-of-the-art hybrid coiled tubing rig by drilling a few inexpensive microbore wells to about 1,200-1,400 ft in the Niobrara chalk formation along the Kansas-Colorado border. The results far exceeded expectations, with drilling cost savings averaging 38%, DOE said.

It said the project's initial success and strong commercial follow-up also demonstrated the potential for coiled tubing drilling of exploration and development wells in the Lower 48 states. For the first time, a Canadian coiled tubing drilling company, Xtreme Coil Drilling Corp. of Calgary, is drilling grassroots wells in the Lower 48 for Anadarko Petroleum Corp. Xtreme Coil is using its newly patented coiled tubing design to drill wells in the aging, marginally economic, shallow oil fields of Colorado's Denver-Julesburg basin.

By the end of this year, said DOE, Xtreme Coil also is expected to deploy its coiled tubing drilling at depths as great as 10,000-12,000 ft in deep gas fields such as Pinedale and Jonah in Colorado's Green River basin for another operator, EnCana Oil & Gas (USA) Inc.

DOE said that microhole coiled tubing drilling technology has the kind of game-changing potential that could be applied to bypassed resources in thousands of oil and gas reservoirs across the US, particularly for shallow reservoirs in mature or even apparently depleted fields.

It estimates the volume of bypassed oil in US oil fields at less than 5,000 ft subsurface at more than 218 billion bbl. Recovering just 10% of this targeted untapped resource equates to an amount equal to 10 years of oil imports from the Organization of Petroleum Exporting Countries, at current rates, it said.

Contact Nick Snow at nsnow@cox.net.

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