Logging tool deployment technology sets record in Alaskan well

June 3, 2002
Forest Oil Corp., Denver, successfully completed openhole logging operations with drill pipe-conveyed memory logging tools to a depth of 20,203 ft MD in its Redoubt No. 4 delineation well in Alaska's Cook Inlet.

Forest Oil Corp., Denver, successfully completed openhole logging operations with drill pipe-conveyed memory logging tools to a depth of 20,203 ft MD in its Redoubt No. 4 delineation well in Alaska's Cook Inlet.

Crews deployed the logging tools at the end of the drillstring with the Compact Well Shuttle from UK-based Reeves Oilfield Services Ltd., which the companies report is a record well depth for the logging tool deployment technology.

The well shuttle houses the battery-powered memory logging tools within special drill-pipe joints, attached to the bottom of the drillstring, protecting the tools from bad hole conditions and the rigors of running into high angle, extended-reach wells.

The rig can rotate and reciprocate the drillstring to assist in reaching bottom.

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Once the drill pipe is on bottom, technicians drop a device called the messenger, which the rig pumps down the drill pipe until it engages the shuttle (Fig. 1).

Further pumping locks the messenger to the shuttle, breaking shear pins, forcing the logging tools out of the drill pipe and into their final deployment position in the open hole.

The system retains drill-pipe mud circulation after the logging tools deploy, which allows the rig to pull a dry drillstring.

Alaskan well

Forest Oil said it faced a challenging drilling environment in the Redoubt No. 4 well, caused in part by clays swelling into the hole.

According to Forest Oil's drilling manager, Paul White, poor wellbore conditions would have prevented openhole logging with a conventional electric logging unit or with wireline-based, drill pipe-conveyed logging.

The successful shuttle logging operations lasted 19.5 hr and recorded formation density, porosity, resistivity, hole size, and gamma ray data.

Forest Oil drilled the well with 60° maximum deviation angle and with 8.5-in. and 6.75-in. drillbit sizes, over the logged interval. Density caliper showed ledges and extensive washouts, however, to more than 15 in.

According to Reeves, it would have been highly unlikely that wireline-conveyed logging tools would have slid past the ledges.

The companies said that wireline based, drill pipe-conveyed logging could have taken as long as 72 hr, and with low probability of success, demon strating that the well shuttle technology reduces rig time and costs during logging operations.

Redoubt No. 4 was the deepest well shuttle operation performed to date, where an operator used the technology to recover openhole log data after ruling out other logging methods, say the companies.

Analysis of the logs revealed 229 ft of net oil pay in the Hemlock formation, below 18,872 ft.

The well logs revealed that the lowest oil in the reservoir extended 50 ft deeper than previously known and encountered no oil-water interface (OGJ, Apr. 22, 2002, p. 8).

Drilled to determine the downdip limit of the Redoubt Shoal field, according to Forest Oil, the Redoubt No. 4 at 20,203 ft MD is the deepest deviated well in the Cook Inlet.

Canadian well

In an earlier application of the Compact Well Shuttle technology, Canadian operator EnerMark Inc., now part of Enerplus Resources Fund, Calgary, used the shuttle to deploy drill pipe-conveyed memory-logging tools for a complex openhole logging operation.

The Compact Well Shuttle equipment, shown on Forest Oil's Alaskan Redoubt Shoal field platform, consists of three subs that thread to the bottom of the drillstring. Compared to wireline-based, drill pipe-conveyed logging, the shuttle-deployed, memory-logging operations require no wireline-skid unit. The memory-logging tools download the openhole log data to a personal computer (Fig. 2). Photo courtesy of Reeves Oilfield Services Ltd.
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The operator drilled the well vertically to a shallow kick-off point at 490 ft and built angle at a rate of 6°/100 ft to the end-of-build section at 1,640 ft.

The operator held angle at 65°, drilling to TD at 6,060 ft with a 77/8-in. drillbit.

Although it would have been technically possible to log the well using wireline-based, drill pipe-conveyed logging tools, several logging companies were reluctant to take the job due to the well's complexity, likely job duration, and high job-failure risk.

Crews performed the job in 14.5 hr using the shuttle technology and drill pipe-conveyed, memory-logging tools, even though the rig pulled the drill pipe in single joints rather than double or triple stands.

EnerMark reported that it had obtained good quality logs in six additional highly deviated wells, in its 2002 drilling program, which it said was imperative for proper completion in the Viking formation.