Mud serves as multipurpose tool in $100B shale industry
Mud makes it all possible.
The $100 billion industry arising from the so-called shale boom — gas drilling that some consider a revolution and others lament as an environmental tragedy — hinges on the lubricating, cooling, cleaning, balancing and communicative powers of drilling mud.
“Every component on that rig has something to do with that mud,” said Andrew Zeni, rig supervisor for Consol Energy Inc. “You couldn't drill a Marcellus or Utica well without mud.”
This rather unsophisticated-looking brown sludge is a multipurpose tool carefully concocted, mixed and managed to clear a path for gas to surface from 7,500 feet below.
Drilling mud, sometimes called drilling fluid, costs as much as $300 a barrel, about a quarter of total drilling costs for one well, according to Cecil-based Consol. Mud expenses alone could be as much as $150,000 per well, which requires about 500 barrels of mud on average but varies depending on the how the shale formation reacts, Zeni said.
The mud's journey starts in large mixing containers on a well pad, where a mud engineer might add barite clay, calcium chloride and other chemicals to a mineral oil base. Recipes vary by company, shale and location.
The mud is mixed, piped to the rig and pumped into the hole through openings in the drill bit. It lubricates and cools the hot bit as it turns 170 to 200 revolutions a minute into the ground, cleaning the hole by clearing out pieces of the freshly cut earth.
“When you drill, Mother Earth isn't sitting there; she's pushing back with her natural force, so in order to constrain that pressure that's coming back, this is where the art of drilling mud comes in,” said Gianni Clemons, chief technical officer of Unique Drilling Inc., based in Dallas.
First line of defense
Unique Drilling mixes and manufactures mud for production companies in the Marcellus formation and drillers worldwide, including Abu Dhabi, Nigeria and Saudi Arabia.
“The mud has to be heavy enough to hold back the formation pressure, but it has to be light enough not to fracture the formation,” Clemons said.
This makes weight for proper mud-shale balance paramount. Mud is weighted with clay and chemicals to push back against the gas it encounters underground.
“You're basically over-balancing the formation, keeping the gas where it needs to be,” said Consol's Zeni.
Getting that balance right helps prevents an explosion, because leaking gas could be ignited on a well pad filled with high-powered equipment.
“It's the safest thing we have out there. It protects everybody,” Zeni said. “The mud is your first line of defense, especially with areas with lots of pressure.”
Companies can buy or lease drilling mud, and its corresponding mixing and piping systems, from oilfield service companies.
Consol leases its mud systems from Baker Hughes Inc. and contracts with the Texas company to mix and manage it along directional drilling. Baker Hughes bills by the cubic foot for the mud, and Consol might use as much as 5,000 cubic feet in one day of drilling, Zeni said.
Because mud is a large expense, companies reuse as much as possible. Its lifespan lasts an average of 10 wells, he said.
Every 12 hours, Zeni gets a report from his mud engineer, outlining the weight, gas levels and chemicals in the mud.
“There are so many little factors to that mud, it's not even funny, but it's come a long way,” he said.
Science of mud-making
Today's drilling mud made of oil, clay and chemicals originated as the dirt-and-water variety favored by pigs.
Mud's usefulness reportedly was discovered in Spindletop, Texas, in the early 1900s when cattle ran through a wet field and a frustrated driller threw the resulting mud into a drilling hole to shore up the earth around it.
Engineering mud has become a craft.
Most mud engineers graduate from a company training program and spend their days monitoring their product, testing recipes in a trailer-laboratory at the well site.
It's an art and science, finding those ratios to get the right balance and ensure the mud plays nicely with a specific section of shale.
“We always test those drilling muds, apply them under simulated conditions to make sure that we have a good outcome,” Clemons said.
Mud can be water-based, synthetic-based with a mineral oil, or diesel-based, though diesel-based fluids are rare.
“You may have 13, 14, 15 different additives that go into making a homogenous fluid,” Clemons said. “We mix whatever they want.”
As it cleans and cools during drilling, the mud starts talking, in a sense, when it responds to electric pulses sent above ground.
“It sends that electrical pulse through mud, telling the tool what it wants it to do,” Zeni said.
In fracking operations, the mud helps guide the drill bit as it makes a horizontal swing out from the vertically drilled hole, carrying its location to an engineer who drives the direction of the bit 1.5 miles below the surface.
“It's almost like Morse code through mud, and it reads a certain signal and it knows what direction the well bit is facing,” said David Yoxtheimer, a researcher at Penn State University's Marcellus Center for Outreach and Research.
When the mud is pumped down-hole, it circulates and resurfaces. It's dried in machines called shakers; its solid and clay parts are stripped and the mud is remixed with its synthetic base. When mud solids (which are nonhazardous) no longer can be reused, they are trucked to a landfill.
Katelyn Ferral is a staff writer for Trib Total Media. She can be reached at 412-380-5627 or firstname.lastname@example.org.