Woodford well perforated, stimulated without wellbore intervention

Jan. 12, 2009
Modules placed in the production casing string eliminated the need for wellbore intervention for completing a Woodford shale horizontal well.

Modules placed in the production casing string eliminated the need for wellbore intervention for completing a Woodford shale horizontal well.

Philip M. Snider, senior technical consultant for Marathon Oil Co., told OGJ that he believed this was the first time that perforating and fracturing jobs during a well completion had not required through-tubular intervention with jointed pipe, coiled tubing, pump-down techniques, or slick-line tools.

The well with the interventionless completion is the Cana 1-15H, in Canadian County, Okla. The gas well has a 17,267-ft measured depth with a lateral length of 4,100 ft. True vertical depth of the well is 13,177 ft. Marathon spudded the well during July 2008.

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The completion of the 8¾-in. borehole includes a tapered cemented casing string consisting of 5½-in. casing to 62° and 3½-in. casing in the horizontal lateral with 10 modules for perforating and isolating intervals (Fig. 1).

Completion modules

The modules for the interventionless completion are new versions of the Excape casing-conveyed perforating and isolation modules developed by Marathon and marketed by BJ Services Co. and Expro Group (OGJ, Oct. 25, 1999, p. 69, and Sept. 2, 2002, p. 39). The modules consist of perforating guns outside the casing and an integral isolation valve within the casing.

A new feature in the modules allows one to break remotely the glass or ceramic isolation valve or flapper. Breaking the flapper in previous module versions required coiled tubing, jointed pipe, or slick-line intervention.

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Fig. 2 shows the module assembly before and after perforating, after closing of the flapper before the stimulation treatment, and when the hydraulically actuated sleeve destroys the isolation valve.

Two or three hydraulic lines outside the casing provide the fluid for actuating the guns and operating the sleeve. The hydraulic lines will remain intact after firing the guns because the design allows shot direction to be phased.

The lower most gun fires with the least hydraulic pressure and incremental increases in hydraulic pressure fire each successive gun. For instance, the lowermost gun would fire with 2,000 psi at surface and 3,000 psi would fire the next gun.

The module has a perforating gun external to the 3½-in. casing and an isolation device within the casing (Fig. 3). Photo from Marathon.
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The modules are typically 10-20 ft long, although Snider said they could be as long as desired, and 63 ft is the longest run to date.

The Cana 1-15H well had 10 casing-conveyed perforating modules run in the well (Fig. 4). Photo from Marathon.
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The Cana 1-15H well had 10-ft modules spaced closer at the toe and wider at the heel because of rock-stress and fluid-flow friction considerations, Snider said

In the well, the guns fired 10 shots/ft with 5 shots into the formation and 5 into the casing. The guns had Geodynamic Ltd.’s big-hole charges fired into the casing and deep penetrating charges fired into the formation.

Future wells will progress to the company’s reactive metal charges.

After each module fired, the flapper closed and a water frac containing a low proppant concentration stimulated the zone. After each frac treatment, the sleeve in the module destroyed the flapper when the next module up hole fired and closed its flapper to isolate the zone below. Snider explained that the displacing fluid for the lower treatment formed the pad for the next treatment.

The modules also have X-profiles and polished bores in case there is a need to isolate the interval in the future.

Even though Fig. 1 shows all modules at the bottom of the 3½-in. casing, Snider said the Cana 1-15H may have had modules oriented in various directions.

He said, for the well, no attempt was made to orient the modules, and perforation breakdown was not a problem.

Module performance

Snider said that the interventionless completion in Cana 1-15H saved about 2,784 man-hr compared with a conventional completion. He also emphasized that the time saved included 1,000 man-hr during which personnel would have been exposed to higher risk during conventional completion operations, an 84% reduction.

Marathon’s statistics as of October 2008 indicate that it has installed 501 modules in 44 wells with a 100% success. It has attempted to fire 493 modules with only two not firing. Snider attributed one failure to a crushed hydraulic line at the surface and the other one to a Barnett well in which 2-3 years lapsed before attempts to fire the guns were made. In that Barnett well, only one of eight guns did not fire, Snider said.

Marathon believes its 99.6% firing success is slightly better than industry’s overall success due to its more intimate knowledge of the system’s capabilities.

Industry-wide, Marathon’s statistics show that various companies have attempted to install 1,001 modules with 984 successfully installed in 96 wells. In firing attempts, only 23 modules of 946 did not fire (97.6% firing success).

For horizontal wells, the statistics show that companies attempted to install 329 modules and successfully installed 312 in 32 wells. In firing attempts, 13 of 303 modules did not fire (95.7% firing success).