No one knows how many wells are being "fracked" in the state at any one time. With permits in the Marcellus numbering several hundred each year, according to the state Department of Environmental Protection, it's at least a few.

But how, exactly, does it work?

In mid-August, Chesapeake Appalachia took The State Journal to a Marshall County frack job and explained what its crews were doing.

As a brief reminder of terms seen often in the media these days, hydraulic fracturing, or fracking, is the process of blasting water laced with sand and chemicals into a rock formation to create cracks and release the trapped hydrocarbons.

The chemicals make the water thicker, to hold the sand in suspension, and slicker, to speed everything through the pipe, while the sand lodges in the cracks and holds them open.

Fracking a well, West Virginians have come to understand, takes lots of water. How much depends on the characteristics of the rock formation and the length of the well bore, but 3 million gallons seems to be a lower bound.

For its concentrated Wetzel and Marshall county operations, Chesapeake was drawing water from Fish Creek, according to Completion Superintendent Zack Arnold, whose territory includes Wetzel, Marshall and Upshur counties, as well as southwestern Pennsylvania.

But as this dry summer stretched on, the company instead established a water line from the Ohio River to two fresh-water impoundments. That came online in early August.

An impoundment holds 80,000 to 100,000 barrels, according to Arnold -- 3.3 million to 4.2 million gallons.

Anatomy of a Frack Job

On Aug. 19 at Chesapeake's Waryck site in Marshall County, the company and its vendors were fracking three well bores that extended in different directions from the same point on the surface and were just finishing the first stage mid-day.

A video Chesapeake played before the trip explained that drillers create well bores by first drilling down through and beyond the fresh-water zone and casing that length in cement. They then continue drilling down to about 500 feet above the Marcellus layer.

Drillers then angle gradually until they're drilling horizontally within the Marcellus layer, out to 4,000 feet and more -- in each of three directions, in this instance.

They case the horizontal sections, or "laterals," in cement and are ready to frack.

Fracking begins with perforation, Arnold explained.

Operators sent a perforation gun on a 20,000-foot electric line to the end of a lateral and fired it to make holes through the casing and into the surrounding rock. When the farthest sections of all three laterals were "perfed," the perf gun was pulled out.

Meanwhile, at the surface, operators mixed water, sand and chemicals in a "blender."

Pumps blasted the mixed fracking fluid down through the well bores, one at a time, out through the perforations and into the shale.

Those first stages would then be plugged, and second stages -- the next-nearest sections as measured by the length of the perf gun -- could be perfed and fracked.

When all stages were finally fracked -- 10 to 12 stages is the current industry standard, Arnold said -- the plugs would be drilled through and fracking fluid, now under pressure in the shale, would come back to the surface as "flowback."

Several hundred thousand gallons of flowback for each well would give way progressively over a period of one to two weeks to gas, and the wells would then be producing.

Flowback

Chesapeake's current process is to recycle flowback by hauling it to the next site, filtering it and cutting the remaining brine with fresh water.

Although Arnold did not want to say how much water it takes to frack a well, he agreed with a range of 3 million to something less than 10 million gallons.

Although he also did not want to say how much of that returns as flowback, he did say it's a small enough percentage that, when filtered and cut with fresh water, it is not too salty to fracture the next well.

Containment

The surface operation involves careful fluid management.

Chesapeake's best management practices -- more stringent, Arnold stressed, than those required by the state -- include what he described as three levels of containment.

Primary containment is everything after the blender, he said -- all the pipes that carry the fracking fluid.

For secondary containment, every part of the operation that holds liquid, fresh water as well as pre- and post-frack fluid, rests on a layer of heavy-duty, textured 60-mil plastic.

And tertiary containment involves constructed berms running around particular sections of the operation and around the entire pad.

Fluid spilled from anywhere will be contained on the plastic, and the expectation is that operators will be able to pump it up before it tops a berm.

One Chesapeake crew has no other duty than to check for good practices, making rounds at each active site about once a week; in addition, an on-site crew from an outside vendor spends its time checking the berm and plastic for holes.

The state requires spills that leave containment to be reported, but Chesapeake reports every spill even if it stays within containment, Arnold said.