- Buyer's guide
Large Rig Market Profiles: Carving A Niche In Rock
H&H Enterprises Focuses On Work In Difficult Soils
“Conventional TCI drill heads are effective in rock formations of less than 15,000 psi,” says Hockran. “Harder rock decreases the ability to steer effectively and reduces production. These drill heads are excellent for gravel and unconsolidated rock formations as they will not wear out as quickly as a standard ‘dirt’ drill head.
“Air hammers are increasingly becoming a more popular alternative in the HDD rock drilling market. They are very effective for drilling plus-or-minus 6-inch pilot holes in hard rock more than 15,000 psi. In certain very hard rock exceeding 25,000 psi., an air hammer will be more effective and efficient than a mud motor. A limitation with air hammers is that steering is not very effective in unconsolidated formations, and it is sometimes difficult to keep the drilled hole clean. However hole-opening capabilities of hammers are very limited and in our experience are less efficient and effective than traditional hole openers that operate with fluid.”
Hockran emphasizes that effectiveness of the various methods depends of project conditions and that no single tool or method is suited for every type of rock drilling.
While projects in energy shale currently dominate H&H’s workload, Hockran makes clear the company’s versatility is important and bids for new work are not limited to the energy field.
An impressive non-energy project in 2012 was crossing the Potomac River and boring under adjacent wetlands in Washington, D.C.
“The eight-inch diameter pilot bore under the river was 5,000 feet long to install fiber optic cable,” Hockran says. “We set up the 210,000-pound pullback DD210 drill about 200-feet from the bank of the river, drilled down and then under the river bed. The depth was about 100 feet below the river bottom. The project owners didn’t want to take any chance that the cable could be disturbed by dredging or any other activity that might occur.”
Crossing rivers with pipe and cable in this area almost always are made by HDD, Hockran added. State departments of transportation limit suspending cables and pipes from bridges, and excavation typically is not an option.
“The river crossing was a ‘drill-and-leave’ job with drill pipe left in place to be duct for the cable,” says Hockran. “Therefore, no pullback was necessary.