Editor's note: This is part 2 in a two-part series on managing Bakken byproducts. Part 1 can be found here.
Water is a vital part of the complex lifeline that makes drilling in the Bakken oil play so productive.
It's water that is key as a proppant carrier - the material keeping an induced hydraulic fracture open during or after the fracking process. Mixed with sand, gel, ceramics, or other materials the water slurry is injected into the well.
However, what goes in also comes out, in addition to oil. Three to five barrels of wastewater are produced for every barrel pumped down a well in the drilling and fracturing process. In the oil and gas industry, 42 gallons is considered a barrel, whether it's a barrel of oil or barrel of water. While fracturing aids in coaxing oil from the deep bowels of the Bakken shale formation, wastewater produced in the process becomes a major byproduct.
Two types of wastewater are involved in the drilling and fracturing process: Flowback and produced water. Flowback water is wastewater from the fracking process and comes back up through the well bore. That typically amounts to about 600,000 to 900,000 gallons - 20 to 30 percent of what was injected - per well, explained Halliburton's strategic business manager for water solutions Walter Dale. Produced water comes out during the production process during a well's lifespan and is typically injected into a disposal well.
Dealing with wastewater falls under the auspices of the Oil and Gas Division of the North Dakota Department of Mineral Resources. "We regulate all aspects of it (wastewater)," described Oil and Gas Division public information specialist Alison Ritter. That litany includes water storage in tanks, transportation and underground injection.
Depending on the technique an average well within North Dakota's Bakken Formation uses approximately 3 million gallons of water during the drilling and fracturing process, explained Oil and Gas Division underground injection control manager Mark Bohrer. With more than 150 rigs actively drilling on any given day in the state, that's a massive amount of water injected beneath North Dakota - and coming back up - and it must be disposed of properly. Wastewater contains a mix of chemicals, often including sodium, calcium, chloride and potassium, although it's mostly chloride and sodium, Bohrer described.
Because wastewater is high in salt content in North Dakota, the only viable option for wastewater disposal for companies operating in the state has traditionally been transporting it to a disposal well and injecting back down the well bore. A disposal well is a well drilled specifically for disposal or an abandoned oil well.
A disposal well confines wastewater into the underground rock formation within three layers of steel - surface and production casings and tubing. Bohrer heads the Oil and Gas Division's underground injection program.
The major components ensuring adequate disposal include proper disposal well construction, cemented casing and an active inspection program, he said. The goal is to protect North Dakota's underground drinking water sources. All disposal wells have injection zones with above and below shale confining layers, Bohrer described.
North Dakota's wastewater is 10 times saltier than ocean water, Bohrer said. Ocean water contains 35,000 parts per million (PPM) sodium chloride, compared to 250,000 to 300,000-PPM of sodium chloride in wastewater.
North Dakota has about 400 disposal wells. Just how much wastewater they can hold hasn't been quantified but Bohrer said eight wells have been injected with more than 30 million barrels in their lifetime. "Some of those (disposal wells) are still active," he added.
While most water used in drilling is from freshwater sources such as underground aquifers or Lake Sakakawea, Bohrer said the industry has increasing interest in using recycled water.
That's where companies such as Nuverra and Halliburton, among others, enter the wastewater picture. With Halliburton handling the technology and Nuverra the trucking logistics, "H2O-Forward"service technology is gradually making its way into the Bakken. The concept is to recycle both flowback and produced water, Dale explained, and use it in the fracturing process at the next well site. The innovation in the technology isn't to recycle wastewater so it's drinking water quality, he said. "We're not trying to make drinking water, we're trying to make fracking fluid," he said.
The cold, harsh reality is that it's scientifically impossible to treat an impaired water source such as wastewater to make it as clean as drinking water at a price point that provides incentives for the industry to recycle.
Instead, by not pulling ions out of the water and trying to re-create drinking quality type water, filtration technology is used to reduce the amount of total suspended solids (TSS). Total dissolved solids (TDS) are left in the water. Fracking water can contain up to 300,000 PPM of total dissolved solids and still be usable, Dale said. Because recycled water from this technology still contains sodium chloride, it reduces the amount of salt that would normally be added in the fracking process.
For years, the belief in the industry has been that freshwater is needed during fracking and drilling. Three years ago a study indicated North Dakota's Bakken wastewater was too salty to be recyclable. "We're saying you just need to remove some of the suspended solids," Dale said.
The traditional method of dealing with wastewater - using freshwater for every well and disposal well injections of the wastewater - usually involves more than 1,200 truck trips hauling 160,000 barrels of water per well. About 60,000 barrels of that is wastewater, another 80,000 barrels is freshwater used in drilling, and of that, 20,000 is flowback water hauled to disposal wells.
Dale said Halliburton's recycling process means 60,000 barrels of wastewater are hauled to recycling sites, along with another 20,000 barrels of flowback water. That means a total of 80,000 barrels of wastewater are available for use at the next well site.
The need for one new barrel of freshwater is reduced for every barrel of recycled water used at a well site. In addition, that's one less barrel of wastewater injected into a disposal well. The need for a biocide salt additive for clay stabilization is reduced because recycled water still contains salt.
Recycling wastewater hasn't gained the momentum in North Dakota's Bakken as it has in other oil plays in the United States, perhaps in part because freshwater availability isn't as much of an issue as it is in other areas where water is at a premium, such as Texas and Oklahoma. In addition, North Dakota has available disposal wells.
Recycling wastewater won't end truck traffic issues in the Bakken, Dale said, but because less freshwater is required, if done correctly recycling could potentially eliminate 30 percent of the truck miles involved per well.
Another way truck miles could potentially decrease is implementation of a pipeline system that would take wastewater from the well site to a recycling center, Nuverra vice president of investor relations and corporate communications Liz Merritt added. It's an option that is currently under study, she said.
Safety is a primary consideration when transporting wastewater, given its high salinity. Wastewater is highly regulated throughout the process and Merritt said it's of the utmost importance that Nuverra's operators meet and perform to all standards of equipment and training. Nuverra has a long-standing presence in North Dakota transporting and disposing of producing water, but "now we've added recycling into that mix," Merritt said.
North Dakota's oil play is on pace to use about 10 billion gallons of fresh water annually. It costs about $8 per barrel for water and transportation to and from a well site, along with a disposal fee.
Nowadays, dealing with the logistics of wastewater isn't a function of technology, Dale said, because water used in the drilling and fracking process doesn't have to be of drinking water quality. For many companies, it's no longer a function of economics because when viewed on a large-scale, it's more economical to recycle wastewater. "It's really a function of choice, speed, and need," Dale said.
As companies become increasingly interested in using recycled water, so, too, increases the need for monitoring such operations.
That's where the Oil and Gas Division comes in again, Ritter said. The agency regulates treating (recycling) plants as well as on-site recycled water containment systems used in fracking.
Monitoring, regulating, and recycling are all part of the process of trying to make the Bakken's massive amount of wastewater more manageable.