Helicopters Used In Seismic Testing
If you have seen or heard helicopters hovering near your residence in Wetzel County, it’s possible that the Dawson Geophysical Company, contracted by Chesapeake Energy, is doing seismic testing with these helicopters.
With the race on for the Marcellus Shale in West Virginia, seismic testing is being used to assist in the drilling process. Chesapeake Energy has hired Dawson Geophysical Company to assist them in this process.
Since the discovery of more advanced gas drilling methods, the Marcellus Shale has been targeted as the next massive U.S. natural gas reserve. The shale, a vast subterranean sedimentary rock formation, contains trillions of pounds of natural gas.
Chesapeake is the largest leasehold owner in the Marcellus Shale play that spans from northern West Virginia across much of Pennsylvania into southern New York, according to the West Virginia Surface Owners Rights Organization According to Chesapeake’s Web site which contains information about seismic testing, the rugged terrain of the Appalachian Basin makes it difficult to transport and position vibrator trucks to conduct seismic surveys. Steep mountain ridges and deep hollows provide uneven purchase for vibroseis trucks.
Chesapeake has literally risen above these problems by using heliportable equipment when it conducts seismic surveys in the challenging West Virginia environments.
“Because of the mountain terrain here, this is an environmentally friendlier way to accomplish seismic data gathering,” said B.J. Carney, Senior Geophysicist-Appalachia. “It leaves a smaller footprint because we don’t cut roads or haul in heavy trucks or equipment. Instead, we surgically drop drills between the trees with no loss or damage.
How this works is a process. First a small shothole drilling rig is delivered by helicopter, attached to the end of a 160-foot cable. The 12-by-4 foot drill is carefully lowered into position and untethered from the hovering helicopter.
Second, a 20 to 40 foot bore is drilled and small charge of explosives is set in the bore hole. The helicopter then picks up the drill and moves it to the next drilling position. This is repeated until the area being surveyed is filled with a grid-like pattern of charge-filled bores, often 50 per square mile.
Next, a grid of geophone receivers are set over the entire survey to record the reflection of sound waves.
Fourth, radio signals trigger the explosive charges deep in the earth to created the sound waves required for measurement.
“From this point, the process is the same as using vibroseis,” said Carney. “It’s a very expensive process-about four times the cost of conventional seismic. Chesapeake is willing to push the edge of the envelope, taking more risk for higher rewards. And here in the Eastern Division, that is starting to pay off.”
Chesapeake had budgeted more than $300 million for seismic data in 2008.