Fracking 101: Here’s the inside mud on how the process works
Glossary of terms
Blender: The equipment used to prepare the slurries and gels commonly used in stimulation treatments. Modern blenders are computer controlled, enabling the flow of chemicals and ingredients to be efficiently metered and requiring a relatively small residence volume to achieve good control over the blend quality and delivery rate.
Casing: Steel pipe cemented in place during the construction process to stabilize the wellbore. The casing forms a major structural component of the wellbore and serves several important functions: preventing the formation wall from caving into the wellbore, isolating the different formations to prevent the flow or crossflow of formation fluid, and providing a means of maintaining control of formation fluids and pressure as the well is drilled. The casing string provides a means of securing surface pressure control equipment and downhole production equipment, such as the drilling blowout preventer (BOP) or production packer. Casing is available in a range of sizes and material grades.
Completion: A generic term used to describe the events and equipment necessary to bring a wellbore into production once drilling operations have been concluded, including but not limited to the assembly of downhole tubulars and equipment required to enable safe and efficient production from an oil or gas well. Completion quality can significantly affect production from shale reservoirs.
Drilling rig: The machine used to drill a wellbore. It includes virtually everything except living quarters. Major components of the rig include the mud tanks, the mud pumps, the derrick or mast, the drawworks, the rotary table or topdrive, the drillstring, the power generation equipment and auxiliary equipment.
Hydration unit: This unit mixes the water and chemical additives to make the frac fluid. Usually the blending process takes a few minutes for the water to gel to the right consistency.
Missile: The missile is comprised of a low-pressure side and a high pressure side, and is the manifold through which the frac fluid flows to the pressurization trucks, and into the wellbore to frac the rock.
Roughneck: A floor hand, or member of the drilling crew, who works under the direction of the driller to make or break connections as drillpipe is tripped in or out of the hole. On most drilling rigs, roughnecks are also responsible for maintaining and repairing much of the equipment found on the drill floor and derrick.
Roustabout: Any unskilled manual laborer on the rigsite. Roustabouts are commonly hired to ensure that the skilled personnel that run an expensive drilling rig are not distracted by peripheral tasks, ranging from cleaning up the location to cleaning threads to digging trenches to scraping and painting rig components.
Shale: A fine-grained sedimentary rock formed by consolidation of clay- and silt-sized particles into thin, relatively impermeable layers. It is the most abundant sedimentary rock. Shale can include relatively large amounts of organic material compared with other rock types and thus has potential to become a rich hydrocarbon source rock, even though a typical shale contains just 1 percent organic matter.
Tank battery: A group of tanks that are connected to receive crude oil production from a well or a producing lease. A tank battery is also called a battery. In the tank battery, the oil volume is measured and tested before pumping the oil into the pipeline system.
Wellbore: The drilled hole or borehole, including the openhole or uncased portion of the well. Borehole may refer to the inside diameter of the wellbore wall, the rock face that bounds the drilled hole.
Vapor Recovery Unit: A system at a drilling site to recover vapors formed inside completely sealed crude oil or condensate tanks. The vapors are sucked through a scrubber, where the liquid trapped is returned to the liquid pipeline system or to the tanks, and the vapor recovered is pumped into gas lines.
Source: Greeley Tribune research and Schlumberger, a global supplier of oil field technology and equipment.
Editor’s note: This story was originally published in the Greeley Tribune in 2014.
The two- to three-day process of hydraulic fracturing for oil and natural gas is perhaps one of the most misunderstood drilling practices, becoming as bad of a word in some circles as a racial slur.
Entire countries have banned the process.
Environmentalists storm capitals over it, demanding increased regulations, and oil and gas company employees and officials scratch their heads — they’ve been using the same process in oil and gas drilling for 60 years without widespread incidents.
“It’s a perplexing issue,” said Collin Richardson, vice president of operations for Mineral Resources Inc. “People go to a light switch and expect energy to be there, but they don’t think about where it comes from. I don’t think most people understand that without hydraulic fracturing, we wouldn’t have natural gas to provide electricity to our homes or gas in our cars.
A recent study by researchers at Oregon State, George Mason and Yale universities revealed that more than half of the 1,000-plus people surveyed across the nation had no idea what fracking was, and almost 60 percent had no opinion on it.
In recent years, combining hydraulic fracturing with horizontal drilling is what has allowed for the oil and gas revolution that many in the industry say will pull America away from the Middle East in terms of long-term resources and energy independence.
It’s important to understand that fracking is a small part of a much larger operation to get oil and gas from a mile below the surface into storage tanks for market.
Fracking takes about two to three days in what is roughly a 10- to 14-day process of drilling and completing a well.
“Fracking is one of the important parts of this,” said Leen Weijers, vice president of technology and sales for Liberty Oil Field Services, a private contractor that fracks wells for oil and gas exploration companies.
Fracking has always been a part of drilling. The new part of the process is horizontal drilling.
“People don’t equate drilling with fracking,” Richardson said. “I don’t think most people understand if you ban fracking, you effectively ban drilling.”
STARTING A WELL
Companies start the drilling process on about a 3-acre pad of land, which allows for the many trucks that become part of an oil and gas drilling process.
The process begins with vertical drilling. A drilling rig is brought on site to drill the well, which will go to depths of up to 10,000 feet below the surface. This process can take from a week to 10 days, depending on the site.
Drilling stops initially below the water table so the well can be encased in cement to prevent anything from the well leaking into the water table. Once the casing is completed, a 7-inch drill bit will drill more than a mile to get to the formation in which to frack. Once the drill bit hits bottom, or the “pay zone,” the company will drill what is called the “bend,” which is the curve the well takes to get into the horizontal portion of the zone. The bend alone could take up to two days to drill.
Throughout the drilling process, drilling mud is pumped in to cool the drill bit and act as a means for the resulting debris to leave the well.
The horizontal portion of the well then is drilled for an additional 4,000 feet to 10,000 feet, then encased in cement, with a 4-inch metal pipe in the center to allow for the oil and gas to flow to the surface. At this point, the well is just a hole drilled into the ground, with a cement barrier between the pipe, the formations and water table.
The rig is packed up and activity stops until fracking is scheduled. Sometimes it can wait for weeks before a fracking crew is able to get there. Sometimes it takes a couple of days.
The actual fracking process uses a lot of machinery capable of driving the fluid down more than a mile, and a lot of science to calculate the exact mixtures of everything from chemicals and water and sand to the pressure it takes to crack tiny little fissures into rocks, more than a mile beneath the surface.
Sand, water and chemical additives are pumped into the well at high pressures, so as to crack the rock in different stages in the horizontal (parallel to the surface) portion of the well.
The chemicals do not erode the rock to create the cracks — it’s the high pressure of the water that opens them up. The chemicals, such as guar gum, which also are in many foods we eat, are added to help the water to gel, allowing the sand an easier vehicle in which to move.
“When it’s thicker, it does a better job of carrying sand downhole,” Weijers said. “If you think about a handful of sand at a lake, and you put it in water, the sand will settle quickly to the bottom of the lake. We don’t want that to happen in fractures.”
Those cracks, now held open by the tiny kernels of sand, release the trapped oil and gas inside, which flow back to the surface after the downward pressure from fluids is released from the well.
Soap ingredients also can be added to the gel to prevent bacterial growth in the well. If bacteria forms, it could release deadly gases.
“You put a lot worse stuff in your food, your yard or your garden,” Richardson said. “A lot of the chemicals are used to clean your counters, and put in your make-up.”
To handle the sand, water, chemicals and production that comes out of the well during the fracking of the well (commonly called flowback), the site needs have the basics: Trucks, trucks and more trucks to carry the water, the sand and the chemicals to mix them all together, and more truck horsepower to combine it all to shoot down through a pipe into an 8-inch hole in the ground.
To prep the area, several 500-barrel tanks for water storage or a massive, 40,000-barrel pool to store water is erected on the periphery of the site. Sand storage tanks arrive, then are filled. A typical frack job will utilize from 1.5 million to 6 million pounds of sand.
Iron trucks carry massive amounts of pipe that will be used to keep the well opened and separate from the well.
“When the rest of the crew arrives on location, they’ll typically rig up to the well head with a missile,” Weijers said.
The missile is a manifold around which most of the activity centers, to ultimately pump fracking fluid downhole. Crews will line on each side of the missile five to six semi trucks, which contain the horsepower to create enough pressure to pump the fluid downhole at the proper rate.
In addition to the horsepower trucks, there are sand trucks and trucks containing the chemical additives to thicken the water to keep the sand moving in the well.
A hydration truck, through which the chemicals are added to the water to “gel,” and a blender, which mixes that fluid with the sand, are nearby. All surround the missile in a horseshoe shape.
“The blender sends the mixture of sand water to the low-pressure side of the missile,” Weijers said. “From that missile, we have 10-12 connections to the individual horsepower units, which really pressurize the mixture of sand and fluids so the (missile) can send it (through its high-pressure side) downhole at pressures that can crack the rock open.”
That one process is good for one frac, or stage, at which the horizontal well is cracked from being hit at such high pressures.
A typical well can have 20 fracs, each necessitating this procedure of blending, pressurizing and cracking. A typical frac job can last up to 20 hours — one frac stage per hour — from start to finish.
At the open end, or the top of the horseshoe, is a data center, or a trailer containing about five to six people controlling the science of the job. There’s usually a representative or two from the oil and gas company, a job supervisor and an engineer to do the calculations.
“Typically, there’s an engineer who makes the readings of the pressure,” Weijers said. “There’s hundreds of parameters being tracked, all the chemicals, the proppant (sand) being pumped, pressures during the job. The engineer makes it possible to track that and do scientific calculations of the data.”
Here, employees track every aspect of the job, from pressures of the fluid to the diesel engine’s fuel gauges.
At various other open areas, there will be containers in which the used sand and production waters are placed into once they fulfill their purpose in the wells to be hauled off later for recycling, injection or disposal.
On jobs where crews utilize a large pool of water, the water is usually being heated to temperatures of about 70 degrees to provide the perfect chemical combination with the additives and sand.
At some point in the drilling and completion process, crews will build oil and gas storage tanks, vapor recovery units to control air emissions, and oil and gas separators for the eventual well production. All will be strategically located around the wellhead.
Once all the fracs are created, the downward pressure is removed from the well. Within a couple of days, the release of that pressure will reverse, allowing the oil and gas to flow from the rocks and up the well.
“At end of the frac job, the flow stream is reversed,” Wiejers said. “Instead of pumping things downhole, due to the pressure we created, we have almost no pressure at the surface, then the flow reverts and oil and gas and some of the water find their way back from downhole to the surface.”
All the equipment is removed from the site, leaving only the wellhead, the storage tanks, separators and emissions control. Production can last for years.
Support Local Journalism
Support Local Journalism
Each donation will be used exclusively for the development and creation of increased news coverage.
If you don't follow the rules, your comment may be deleted.
User Legend: Moderator Trusted User