McMULLEN COUNTY — Chesapeake Energy Corp.’s rig jutted 165 feet into the sky and sat off a rocky road that was a long and jolting ride from the nearest paved stretch in a remote part of the county.
The rig punched a hole 9,278 feet down — more than a 13/4 miles — before turning a corner to bore 6,408 feet horizontally through the Eagle Ford shale in South Texas, a vast formation under 24 counties that stretches 400 miles from East Texas to Webb County and the border.
In just the past few years, technological advances, including horizontal drilling and a technique called hydraulic fracturing, have made it possible to tap the oil and natural gas trapped in the Eagle Ford’s tight rock.
It costs about $7 million to drill and complete a well using hydraulic fracturing in the Eagle Ford shale, Chesapeake spokesman Silver Vasquez said.
After a well is drilled vertically, precise technology allows the drilling to move horizontally through the shale.
In fracking, the horizontal section of the well uses a tube inserted through well casing that carries explosive charges to perforate the shale at intervals about 50 to 80 feet apart.
The tube is pulled to the surface. Then high-pressure pumps send a viscous mixture of water, chemicals and sand down into the horizontal casing.
When the fracturing fluid reaches the fissures in the shale, pressure builds until the shale formation fractures. More fractures are created along natural zones of weakness in the shale.
Proppant — sand or ceramic pellets — added to the fluid helps keep the fractures open so oil and natural gas can flow into the well casing and to the surface.
On a recent day near Catarina in Dimmit County, Chesapeake was fracking a well with the help of seven different contractors.
The air throbbed from the din of 18 trucks, most pumping the water mixture down the hole. Sand gushed down a chute from trucks that had rumbled up to deliver 45,000 pounds of sand each.
Fracking usually continues in stages, with some wells fracked as many as 20 times. Chesapeake planned to frack the Dimmit well in 18 stages along the horizontal. The fracking operation was expected to last from three to five days, with the work starting at 6 a.m. and ending about 9 p.m.
“The technology to do this just wasn’t available 10 years ago,” said Glen Foster, a senior completion foreman for Chesapeake. “The drilling fluids and the quality of the drill bits have made the difference.”
When fracking is completed, the pumping trucks go away. Then a network of valves is installed at the wellhead — known as a “Christmas tree” — that regulates the well’s flow. The oil and gas then goes to storage tanks or a pipeline and on to a refinery or processing plant.