By Steve Ferris, for the Greene County Messenger
A group of roughnecks wrangle 3,000-pound sections of drilling pipe into a â€œstringâ€ measuring thousands of feet long and steer it to a sweet spot filled with natural gas more than two miles away underground.
ï»¿Tapping into lucrative Marcellus shale gas deposits is labor intensive, but it is accomplished using technology that early gas and oil drillers could have only imagined.
Chevron, one of the leading gas and oil producers in the country, displayed that technology and manpower at a well on farmland the company leases in Monongahela Township.
From five well heads just 15 feet apart in the center of 20 acres of a hilltop that was leveled to form a pad at the Greene County farm, Chevron and Crown Drilling, an outfit partially owned by the energy company, drilled five holes 4,000 feet deep and 8,500 feet horizontally in different directions.
Handling the pipe and guiding the string through the curve, or the â€œheel,â€ from the vertical bore to the horizontal bore while making many small steering adjustments to reach the sweet spot, a 100-foot-thick Marcellus layer under the leased property, is accomplished by modern-day roughnecks who rely on computers and automation.
A hydraulic catwalk machine lifts and carries the pipe to the well head. Two men working outside on a 24-foot-high platform nudge the machinery that screws the new sections of pipe to the string. The platform is right outside of the window of an enclosed, climate-controlled cabin where the drill operator runs and oversees the operation using six computer monitors, control panels, a keyboard and a phone.
Drill site manager John Turner, a Texan with 36 years experience in land, off-shore, domestic and international gas and oil exploration, said it used to take four men just to attach new sections of pipe to the end of a string.
Technology in use at the business end of the string helps the drill operator steer the drill bit to the relatively narrow layer of decayed organic material that is the Marcellus shale formation.
The drill pipe string flexes just enough to be steered from the vertical bore through the heel to the horizontal bore.
â€œThe pipe is just flexible enough,â€ said Greg Hild, Chevron\’s Marcellus manager. â€œEight thousand feet of pipe becomes flexible, like a noodle.â€
Sensors in the bit detect the direction, angle and depth, and transmit the data to the operator and to a control trailer where a group of workers monitors the same information. The sensor has to be angled slightly upward to offset gravity, Hild said.
The drill operator relies on a special sensor that detects the low level of radioactivity emitted by the Marcellus shale to steer the drill bit to the shale, he said.
The information is transmitted through manufactured mud that is pumped through the pipe and drill bit to push rock cuttings along the outside of the pipe to one of several lined pits on the surface, Hild said. The mud also lubricates and cools the bit.
â€œMud is the secret to drilling,â€ Turner said.
The temperature of the mud and weight of the string on the drill bit are other bits of crucial information sent to the surface.
A cylinder-shaped mud motor is attached to the drill bit. The mud motor pushes the mud to the bit and nozzles in the drill bit discharge the mud, Hild said.
A mud engineer tests the mud several times a day to check its consistency and to make sure it is made of the proper mix of 56 percent synthetic mineral oil, 22 percent solids and chemicals and 20 percent water, Hild said.
The mud is designed not to chemically react with the dirt and rock it comes in contact with and it helps prevent the bore from caving in, Hild said.
The drill bit and the mud motor are the only parts of the string that rotate during horizontal drilling, or â€œslidingâ€ as Turner calls it.
Drill bits measure about eight inches in diameter and have cutting heads with teeth made of tungsten, carbide or synthetic diamonds. The type of bit used depends on the kind of rock that has to be drilled through or circumvented.
Bores are drilled in sections. The first 350-foot-deep section is drilled through the freshwater aquifer using an air-powered drill. No mud is used to avoid contaminating the aquifer, which is the source of water for wells, Hild said.The bore is 16 inches in dameter and is supported by a steel casing and cement.
The next section is 700 feet deep where the coal seam lies. A second layer of steel casing and cement are set in place to isolate the seam. This hole is 11 inches in diameter.
A third layer of casing and cement extends 2,700 feet down forming the intermediate bore, which is 8 5/8 inches in diameter.
The fourth string of casing extends for the length of the well bore. Every layer of steel casing and cement extends to the surface, which means there are eight barriers, four layers of steel and four layers of cement, in section through the freshwater aquifer.
Equally important to the drilling operation is electricity. On-site generators produce thousands of watts of power that drives the drill and all the pumps, computers and lights at the well site. The generators were the only major sources of noise at the drill site.
The last task at a well site for Crown\’s 13-man drilling crew is to pack up all the generators, the drill rig, trailers, pumps and other equipment to take it all to the next site. It takes 40 to 50 truckloads to transport all the gear.
Another contractor working for Chevron hydraulically fractures, or fracks, the well.
Fracking, is a technique invented about 50 years ago to fracture underground rock formations to allow gas to be extracted. The process is just as technologically driven as drilling.
Chevron\’s fracking contractor, Universal Well Services, sends a perforation gun, another cylindrical device, down the casing to the frack sites in the bore and detonates shaped explosive charges in the gun to open holes in the casing. Wells are fracked through the holes in the casing.
A mixture of water, sand and chemicals is pumped through holes at each frack site, which is known as a stage, under 9,000 pounds per square inch (PSI) of pressure to fracture the shale formation. The sand keeps the frack open, allowing the gas to be extracted, Hild said.
At a well being fracked near Smithton in Westmoreland County, 18 trucks with 2,500-horsepower turbocharged diesel motors affixed to the beds do the grunt work, but a contingent of 70 workers keep their eyes on the equipment, monitors and materials.
The truck-mounted motors operate pumps that force the water, sand and chemical mixture through the well bore.
The motors and pumps are wired together and to a control trailer were workers monitor the pressure at the well head, pump rate and the amounts of sand and water being used. Those readings are transmitted in real time to computers in the company\’s Marcellus division office in Moon Township where engineers monitor the process, Hild said.
Water is stored in ponds with nearly 2 million gallons of storage capacity and sand is stored in large, enclosed truck trailers. The water, sand and chemicals are mixed in blenders before being pumped to the well head.
In one of three wells at the Smithton site that Universal\’s crew was fracking, the horizontal bore had 12 stages.
The rumble from the idling motors swells to a thundering roar as the rotations per minute (RPMs) are remotely increased from the control trailer to crank up the pumps to frack one of the stages with 400,000 gallons of water, 350,000 pounds of sand and the chemicals.
The mixture is pumped into the well at a rate of 4,200 gallons a minute. It takes about two hours to fracture a stage.
The chemicals include a friction reducer that helps the fracking mixture flow through the pipe, a bacterial preventer, scale inhibitor and an iron inhibitor.
It takes about a month to level the well pad, two months to finish the vertical and horizontal drilling and a month to complete the fracking.
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