Tom's Life Bits

By Tom Wilber twilber@gannett.com

DIMOCK – Will reaping the riches of the Marcellus Shale carry threats of random explosions?

Scientists and industry officials are working on an answer in Dimock Township, Pa., where gas originating 1,500 feet deep or more seeped into water supplies feeding homes.

Cabot Oil & Gas, of Houston, has taken four water wells off line at homes in the Carter Road area and is venting nearby natural gas wells suspected to be related to the problem. The intensive investigation began after a water well exploded Jan. 1.

Tests have traced the gas causing the problem to the Devonian Formation, which includes the Marcellus Shale, said Mark Carmon, spokesman for the Pennsylvania Department of Environmental Protection.

Cabot wells being drilled in Dimock extend through the top of the Devonian into the Marcellus, about 6,000 feet deep.

One theory is gas above the Marcellus – trapped in the upper part of the Devonian – traveled up the well bores and escaped into the aquifer through gaps in the well piping, Carmon said.

Drilling crews start with 7-inch diameter pipe near the top of the well bore. Through that, they insert 4-inch pipe into the bottom of the well bore to reach the depths of the Marcellus. The gap between the small pipe telescoped through the larger pipe is called annular space.

Devonian gas, under pressure from the earth, would seek the path of least resistance, which could be spaces in the well casing or pipes.

To test the theory, Cabot is cementing off the gaps in several suspect wells. Crews are working on that job this month, said Ken Komorowski, a spokesman for Cabot. They have been slowed somewhat by severe weather and the need for special equipment to be shipped to the site.

Meanwhile, they are routinely testing natural gas concentrations in at least nine nearby properties to see whether they can establish a cause-and-effect relationship between levels found in water and work being done on the gas wells.

“We have a hydro-geologist working through plausible theories,” Komorowski said.

The investigation is important to ensure the safety of Dimock residents, Carmon said. It also goes beyond that.

“We need to see whether this is something that could happen someplace else,” he said. “In a way, this is like one big experiment in the field.”

Dimock is about 15 miles south of the Broome County border. The findings could be especially significant to Southern Tier residents, living over the same geological formations.

The Marcellus, running under the Southern Tier and throughout Pennsylvania and the Appalachian basin, is the target of intensive drilling efforts by Cabot and other energy companies seeking to develop it into a major national energy source.

In Broome County, several companies holding mineral rights to the Marcellus, including XTO Energy and Chesapeake Energy, are waiting for the results of an overhaul of drilling regulations by the New York State Department of Environmental Conservation. The DEC, meanwhile, is tracking events in Dimock, said Lori Severino, an agency spokeswoman.

Drilling into the Marcellus under Broome County would begin after the regulatory updates are completed, which is expected later this year.