The equipment needed to drill more than 1.6 kilometers (1 mi.) underground would not be unfamiliar in areas like coastal Texas or the North Sea, where offshore drilling is commonplace. In Tioga County, Pennsylvania, though, the presence of a 76.4-centimeter (34 in.), 2,423.7-kilograms (4,497 lb.) bit with .96-centimeter (.38 in.) tungsten-carbide buttons on the drilling surface is a little out of the ordinary.
For N.E. Hub Partners L.P., the group spearheading construction of an underground natural gas storage facility in northern Tioga County, the unusual drill bit is what is necessary to grind through the shale, sandstone, anhydrite and other less-than-malleable materials of which this rocky, mountainous area is composed.
Impressive enough on its own, the bit is powered by an imposing Champion RC300 hammer weighing in at 5,213 kilograms (11,584 lbs.). Its outside diameter is 71 centimeters (28 in.); its overall length is 236 centimeters (93 in.); and its shoulder-to-bit face is 279.4 centimeters (110 in.).
Jim Browning, consultant for Continuous Operations Inc., a company working with N.E. Hub Partners on the Tioga Gas Storage Project, explained that the large bore design of the Champion RC300 “provides high performance levels as associated with other Numa [Numa Manufacturing, of Connecticut, makers of the drill and hammer] down-hole hammers.”
The hammer is a valveless, pneumatically operated, reverse circulation drill designed to use .76- to .99-centimeter (30 to 39 in.) reverse circulation bits in a wide range of drilling applications, he explained.
“It is specifically designed to provide maximum performance on the drill rigs that are most commonly used in large-diameter drilling applications,” Browning said.
The prize in the this mega-drilling operation is a layer of salt that starts at about 141,000 centimeters (4,700 ft.) below the earth’s surface. After a series of wells have been drilled to about 180,000 centimeters (6,000 ft.), water from nearby Cowanesque Lake will be used to leach caverns in the salt layer.
Pipeline-quality natural gas will be stored in the caverns; the salt will be processed for commercial and industrial use at a facility to be constructed in a neighboring township.
Integral to the drilling process is a DR40 Foremost Barber rig. With this, the drill itself rotates clockwise while the casing rotates counterclockwise. This prevents the drilling rod from unscrewing, Browning said, adding that, “advancing the casing as you go” helps to counteract cave-ins. Further, as the drilling takes place, cuttings are eliminated via a hose.
Tom Siguaw, project manager, estimated that this initial well will be completed in June. As the drill eats its way further into the ground, the various rigs and drillers which will be called upon each have specific “blow-out prevention practices,” he said. Experts in specialized drilling operations, cementing, laboratory testing, and fabrication will be tapped as well.
“When all is said and done, we have a series of specialists continually involved throughout the drilling and cavern construction process,” Siguaw said.
Currently there are 18 to 20 workers living and eating on site in portable buildings; drilling is ongoing 24 hours a day since mid-February; tons of earth have already been moved — more is moved daily as roads in and out of the project are built and improved. The goal, according to Siguaw and N.E. Hub Partners, is to ensure a ready, deliverable and accessible supply of natural gas to the Northeast.
Construction of 10 caverns is planned, with each holding up to 105 billion cubic meters (3.5 billion cu. ft.) of natural gas.