Shell Western E&P Inc. has begun a coiled tubing drilling program in California's McKittrick oil field that contractor Halliburton Energy Services says is likely the world's biggest.
The coiled tubing work is a big part of a major effort to reactivate an idle steamflood project on the Calso property, section 12-30s-21e, 2 miles northwest of McKittrick, Calif.
Of a total 115 new wells planned for the project, 68 will be drilled with coiled tubing, and 47 will be drilled with conventional rotary tools. The drilling program is expected to take 34 months.
Shell also recently drilled four wells with coiled tubing technology in Kern County's supergiant South Belridge field, the company's first such wells in the U.S.
MCKITTRICK PROGRAM
Shell started the coiled tubing portion of the McKittrick program with a Halliburton Energy Services unit in May.
As of last week, the first 12 wells have been completed. Halliburton is drilling about one well a day.
In the program, 2 in. tubing from a reel is stripped into the well by an arched arrangement of grippers. The downhole assembly consists of a bit on the end of a mud motor on top of which drill collars are run. Fluid circulated down the coiled tubing turns the rotor in the mud motor, activating the bit.
A supervisor and crew of three operators handle the drilling operation.
Wells are programmed to depths of about 775-960 ft to tap the Pleistocene Tulare sand, which produces 11.2' gravity oil.
There are 30 steamflood injection wells on the property at present, all shut in since July 1992. The reactivation project calls for converting the injectors to producing wells. The 115 new wells will serve as injectors.
Total footage is programmed at about 61,000 ft.
The reactivation project does not call for areal or steam volume expansion of the steam drive, which was permitted for injection of as much as 27,200 b/d of water converted to steam.
There are about 100 producing wells on the Calso property, with 25 on line producing about 100 b/d of oil and about 75 wells shut in.
Gene Rutland, Halliburton coiled tubing adviser, says the project likely is the largest coiled tubing drilling project undertaken, especially for new wells. He said it will account for at least one half of all the wells drilled this year using coiled tubing.
COILED TUBING ADVANTAGES
Roy Romagno, Shell drilling foreman, does not expect coiled tubing to replace conventional rotary drilling but believes there will be a place for both in drilling applications.
He credits coiled tubing technology with allowing operations in limited space, basically requiring only an 8 ft by 8 ft square in which to set the jacking frame, making it possible to maneuver among existing facilities.
Like most of the other centenarian giant heavy oil fields in California, McKittrick is crowded with a jumble of steam distribution lines, production lines, power lines, and pumping units that leaves little room for conventional drilling methods.
Another advantage, Romagno said, is savings in rig-up and rig-down time, because the unit does not require a mast, rotary table, or other equipment needed for rotary drilling. With no need for a crew making and breaking connections on a rig floor, there also is less chance of injury.
The technology also boasts environmental advantages, he noted, saying the lower profile operation generates less noise and emissions and, because of a much smaller hole size, a smaller volume of cuttings to dispose of.
Shell's McKittrick project is intended to significantly boost declining production from the old field.
McKittrick production dates to at least the 1860s, when several shallow, low volume oil wells were drilled with cable tools. The field came of age just before the turn of the century when Klondike Oil Co. completed a well that had blown out, flowing 1,300 b/d of oil.
Field production peaked in 1966 at 11.4 million bbl, or 31,300 b/d. In 1993, the field produced 1.15 million bbl for an average 3,150 b/d.
Cumulative production at McKittrick is 273.9 million bbl. Estimated remaining reserves total 9.4 million bbl.
SOUTH BELRIDGE WELLS
Shell's South Belridge coiled tubing wells were drilled to 1,400-1,532 ft.
The latter depth is believed to be the deepest to date in California for a coiled tubing well.
The four South Belridge wells are to serve as steam injectors. Shell used a Dowell Schlumberger unit for the South Belridge wells. The contractor spooled 2 in. coiled tubing from a reel capable of holding 3,000 ft of tubing.
Shell cut 6 in. diameter hole in the first three wells and 61/4 in. hole in the fourth. Wells were cased with 2/s in. tubing run in 30 ft joints picked up with a hydrocrane and made up with tongs from the work floor of the jacking frame.
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