Closed-loop systems: Innovative way to dispose of Marcellus drilling debris

LUCULLUS, Pa. - As Marcellus Shale horizontal wells get bigger, they are producing vast quantities of something other than natural gas:

Drilling debris.

As gas drillers improve their ability to capture ever greater swaths of acreage - some wells now extend laterally nearly two miles - the amount of rock that is brought to the surface in the initial digging process mounts up quickly.

According to Anadarko Petroleum Corp., which is drilling on leased land in Tiadaghton State Forest near this Lycoming County hamlet, a typical horizontal Marcellus well produces more than 1,000 tons of material, about 75 truckloads.

State regulations allow cuttings to be stored in lined pits near the well site. After the drilling is completed, the pits can then be covered in plastic and entombed beneath soil, a kind of mini-landfill.

But horizonal drilling produces so much material that it cannot be easily buried at some drilling sites. Those sites may contain several wells, each producing a thousand tons of cuttings.

Anadarko, which is drilling extensively on state forest land, decided last year to convert all its Marcellus operations into closed-loop systems, eliminating pits and collecting debris in steel containers that are carted to landfills.

It also received state permission to dig up the buried cuttings from about a dozen wells it already had drilled.

"We want to say we haven't buried anything here," said Steve Woelfel, Anadarko's drilling-operations manager in Appalachia. "It always could be a risk. It could come back to you."

As the natural gas industry has come increasingly under a microscope during the Marcellus Shale gas boom, on-site burial is also under scrutiny, although state regulators and the industry maintain the practice is environmentally sound.

The well-drilling process and the cuttings it generates are separate from the controversial practice of hydraulic fracturing, which is done after the borehole is drilled and lined with steel casing and cement.

"Fracking," which involves the high-pressure injection of water, chemicals, and sand into the well to shatter the shale, produces great quantities of toxic liquid wastes. Those wastes can be recycled or treated, but they cannot be disposed of at the well site.