TH60 gets a boost

March 7th, 2012 | Posted by in TH60

Large diameter hole challenges overcome with high pressure air

A U.S.government agency that focuses on environmental sciences was recently drilling an exploratory pilot hole in the Nevada desert in order to observe the water table nearLake Mead. Located over a mile away, well below the elevation of the test well, the lake is receding because of a lack of rainfall, reduced snow melt runoff and increased consumption by the residents of Las Vegas and its surrounding communities.

The well was instrumented with a water level sensor that will collect and relay real-time data via satellite to the organization’s office. The information will allow them to monitor water levels, water quality and yield for several decades.

The crew started drilling with air from the 1070/350 compressor on their Atlas Copco TH60. This rig is outfitted with 70,000 pounds of pullback for deeper boreholes. The organization also has an Atlas Copco XRVS 1000 compressor and Hurricane B4-41/1000 booster to support deep well drilling.

The site is laid out for easy access to plumbing and for observation of gauges by the driller

With all that air power, the crew began at the surface with a 12-inch hammer to drill a 20-inch hole. The plan was to case with 16-inch casing toward the surface, reducing the diameter to 6 inches as the well got deeper.

As happens with many good plans, the formation didn’t want to cooperate. Because of a sandy formation, the versatility of the TH60 drill rig proved useful, converting to mud drilling at about 80 feet (24 meters), continuing to 120 feet (37 meters).

The crew converted to a 14¾-inch tricone bit to do this. The rig has a 3-inch by 4-inch Mission centrifugal mud pump with flow and pressure of 150 gpm at 310 psi. Once they got into competent rock, 12-inch surface casing was set in place.

The formation was described as “red clays and chalky near the surface with carbonates going deeper.” From that point drilling continued with air, supported solely by the rig’s compressor.

It worked well for the crew to drill a 6½-inch pilot hole and then ream the hole with an 11-inch bit. For the 6½-inch hole the crew tried out the Atlas Copco Secoroc Aqua 60 down-the-hole hammer with success. The water table was first encountered at 360 feet (109 meters) below the surface.

At this point, drilling remained well above the elevation of the lake in the distance. To continue drilling the 6½-inch pilot hole, it was necessary to engage the booster at 600 feet (183 meters), where they encountered too much water to penetrate without the booster. Ultimately, the hole was completed without full capacity of the 1,000 psi booster, requiring just 600 psi.

The Atlas Copco XRVS compressor is a two-stage, high pressure unit that the customer used from the deck.

Blake Gearhart, Atlas Copco large compressor business development manager said, “The booster can be used in harsher circumstances and worse conditions, but it also performed well in its lower range for this job.”

Through the monitoring process made possible with the TH60 and high pressure air, the amount and quality of groundwater for one of the world’s most recognized cities, which happens to be in the vast desert of Nevada, will continue to be tracked for future generations.


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