“They said it couldn’t be done,” was Bob Morris’ opening comment. “They” refers to everyone who has ever talked about air drilling the red bed strata in West Texas’ Permian Basin oil patch. Morris, drilling supervisor for Butch’s Rat Hole and Anchor Service Co., didn’t agree with this long-standing assumption.
Scott Bryant, president of Butch’s Rat Hole, is following in his father, Butch’s, footsteps. Butch’s Rat Hole supports the oil patch in Texas, New Mexico, Louisiana, West Virginia, New York and Pennsylvania, doing top-work, including rig moving and anchoring, as well as drilling rat holes, mouse holes, conductor-pipe holes and pre-set surface casing.
Bryant was looking for a faster way to complete the job of pre-set surface casing without having all the ancillary equipment associated with mud drilling. After asking around to other companies that have used top-head rotary drills, he sought out Venture Drilling Supply, and inquired about Atlas Copco’s RD20 drill rig.
Venture salesman Delaney Erickson says when Butch’s called, he did something Venture Drilling Supply had never done before. Butch’s wanted proof that it would work before they bought it, so Erickson would have to demonstrate the rig before they’d buy it.
The test required drilling a 12.45-inch diameter hole 380 feet deep. Erickson used a round-button concave-faced bit on an Atlas Copco Secoroc QL120 HC down-the-hole hammer with the hydro-cyclone option. For the test, Erickson used 4-inch RD20 pipe.
After spudding in on a Thursday afternoon, Erickson drilled to 200 feet the first day, stopping just short of the red bed. The next day, he finished up the hole without much difficulty. He says, “The QL120 hammered all the way to TD (total depth) at 380 feet.” Monday morning, Butch’s held up its side of the deal, and handed Erickson a check for the RD20.
The red bed is a reddish-colored, clay-like shale stratum, roughly 200 feet to 1,400 feet from surface, in the West Texas Permian Basin oil field. Drillers currently use PDC or tricone bits, drilling with mud to raise the cuttings. To drill using air on the first hole, Erickson injected 35 gpm of water, foam and polymer to lift the cuttings. Once drilled, casing was installed immediately because the red bed will swell, making it difficult or impossible to install casing.
Smart Air Power
To have enough air, Butch’s purchased an auxiliary compressor to increase air availability. The company chose the new Atlas Copco DrillAir XRVO 1550 CD7. This open-skid unit offers the greatest volume air available from a single-engine compressor, 1,550 cfm at 365 psi. Combining the RD20’s 1,250/350 air compressor output with the auxiliary compressor brought total free air delivery to 2,800 cfm.Bob Morris says, “I’m really impressed with that compressor. It’s the most intelligent thing on this job site. It’s the one piece of equipment that I can turn on and just walk away from.”
The compressor also works well for the crew because they have all the piping and controls on one side – the dog house side – for easy hookup and monitoring. The company has outfitted an air trailer that sits parallel to the doghouse for easy access.
The last hole drilled by Butch’s crew required both the rig air and auxiliary air with the pressure at 325 psi. They have purchased a booster capable of 700 psi, but have not needed it to date. The next hole the company will be drilling is a 15-inch-diameter hole with the QL120, so they are ready in the event more air is needed.
To assist in cleaning the hole because of a smaller annulus, Butch’s purchased 5-inch RD20 drill pipe from Venture. The crew also is running 5-inch drill collars to put extra weight on the bit.
Extra air was necessary because of the amount of water in this Pecos River area of the Permian Basin. Morris notes they often run into water flowing at 100 gpm as shallow as 100 feet. Morris says doubters told them they would never get through this Windmill water zone because the hammer would water out. “I completely filled the mud pits with water, but that hammer never skipped a beat.”
The Right Tooling
The Hydrocyclone feature on the QL120 is an important feature because of the amount of water involved. The Hydrocyclone has an impeller that diverts water out the top of the hammer. This allows the solution of water, foam and polymer to be injected for maximum cutting removal, while maintaining a maximum penetration rate through air delivery to the piston and bit.Six surface holes have been drilled to date, ranging in depth from 350 feet to 650 feet. In Texas, the Railroad Commission of Texas sets the depth required for each surface hole, generally 100 feet to 150 feet below the water table. The production oil wells that will be drilled later will be 11,000 feet at total depth.
Butch’s RD20 men quickly are becoming old hands. The last 440-foot hole took less than five hours from setup to cemented well. To rig down took 40 minutes. “We had the well drilled in an hour and a half, and that included swabbing the hole three times after each connection. It took longer to set casing than drill the hole,” explains Morris.
For all those who said “it can’t be done,” the proof is in the record books. Air drilling is more than a possibility in the red bed; it now is a west Texas reality.
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