By Sharon Dunn | The Greeley Tribune, Colo.
The answer to Greeley’s first earthquake in at least 40 years may be sitting 10,000 feet below the surface in a deep-water trash can that might be overfilling.
The oil and gas boom has put added stress on the industry’s resources, more specifically in deep wastewater injection wells that cut two miles below the surface. But some say the answer may be as simple as water management.
Wastewater injection wells — which take in produced water from fracking jobs — may now go under increasing scrutiny in Colorado, as scientists have found strong connections between them and a spate of small earthquakes across the country in recent years.
Still, most injection wells are not linked to any earthquakes; it’s only a tiny fraction of injection wells that have specifically been cited as the cause of a minor quake. It’s a puzzle that continues to grow for seismologists looking for answers.
Researchers from the University of Colorado at Boulder put out seismographic equipment throughout Weld County last week, hoping to cull the earth’s secrets into a database of answers. If injection wells are found to be the common denominator in further quake activity, they’ll capture it.
But in the absence of answers, some would say solutions are not that difficult.
“There are ways to fix this,” said Ken Carlson, an associate professor of civil and environmental engineering at Colorado State University. “This is sort of a byproduct of too much water being disposed of, but it’s not like we should shut it down. That’s what the activists will say. It just means we need to improve our water management. So if you say this is probably related to disposal wells, it isn’t that hard to change our practices and really fix this. Just drill new wells and increase recycling.”
WHAT ARE INJECTION WELLS
Injection wells have long been handy tools for oil and gas companies to dispose of wastewater in an environmentally friendly way. The water is pumped two miles beneath the surface into porous rock, through which the water disperses — allowing more water to be pumped in. The process is highly regulated by the Environmental Protection Agency and state oil and gas regulators. Operators must adhere to disposing of water at tested rates and volumes, so as not to overwhelm the well, and they are subjected to annual inspection and well integrity testing every five years, state officials say.
“In a natural system like that, you can do projections. But until you push it to the limit, you can’t really prove it,” Carlson said, noting that he was clearly guessing. “Maybe it’s never been pushed that high.”
For Anadarko Petroleum Corp., which is working to manage its water resources by using municipal effluents, recycling and piping water into sites rather than trucking, officials say they may be coming close to a “limit” on its injections wells, and have been working toward better management to dispose of less.
“The wells are definitely a cause of concern with induced seismicity,” said Korby Bracken, environmental health and safety manager for Anadarko. “We think they’ll continue to be used but it’s something we’re studying quite a bit. There have been multiple studies in Ohio and Oklahoma and other areas where the injection of produced water from oil and gas had the potential to cause induced seismicity. It’s definitely something we’re taking a look at.”
The puzzling part to seismologists is that some areas rife with injection wells for years have no earthquake activity; still others start quaking the minute the well is drilled. There were two injection wells in proximity to the perceived epicenter of the Greeley quake — one was two years old, and the other was 20.
“There are a lot of variables,” said Justin Rubinstein, a seismologist out of Menlo Park, Calif., who is chief of the Induced Seismicity Project, which studies man-made earthquakes. “Maybe this earthquake relieved everything that was available to be relieved or maybe it didn’t and there will be more. Maybe the operator said I might be causing earthquakes, I need to stop injection or slow injections. Generally, when you slow or stop injections, earthquakes slow down.”
The idea of drilling more injection wells to relieve the pressure on existing wells is favored in the exploration community.
Carlson said the water could get dispersed a bit more evenly, reducing pressure with the oil and gas boom going on in Weld.
“It’s not a bucket,” Carlson explained of the rock in which the water is pumped. “It’s more like a sponge. You put the water in and it gets absorbed, then it diffuses through the formation. But you can’t just put in an unlimited rate and keep raising the pressure. Then something would give, and that something might be a fault. With the growth in fracking and unconventional oil and gas in the DJ, there’s certainly greater demand on some of these water disposal sites.”
Rubinstein said he wasn’t so sure drilling more injection wells is the answer.
“In a different perspective, now you’re covering more areas with injections wells, so maybe you’re increasing the probability of finding an area that has a fault,” Rubinstein said. “There are so many variables out there.”
Rubinstein suggested creating mid-volume wells, alleviating pressure that way. “But I don’t know if it gets you out of the problem,” he said.
Anadarko has a permit pending for an injection well. The company has three in Colorado now, all that are running at capacity.
“That being said, we’re looking at other and alternative ways to recycle the fluids that come from the well bore,” Bracken said. “So we don’t have to rely as much on those saltwater injection wells.”
Water, water everywhere
A typical frack job will use 3 million to 4 million gallons of water, but not all of it comes back once the rock is stimulated 7,000 feet below ground. Typically, about 20 percent of the water comes back to the surface during a frack job.
Companies will take that flowback, treat the water on site to take out harmful bacteria from beneath the ground, and truck or pipe it out for recycling or injection. The rest of the water comes out with the oil and gas over time.
Recent years have shown the technology is available to clean up used fracking water, enough to be reused, much like a municipal wastewater treatment system.
“Some operations are pushing ahead with more recycling,” Carlson said. “The more you recycle, the less you’re disposing of and that’s a good thing.”
Anadarko and Noble are big customers of High Sierra Water Services, which operates two recycling facilities in Weld County. Two of their facilities together can recycle about 20,000 barrels a day (840,000 gallons). Both companies have worked on both ends to recycle water.
Anadarko, for example, takes effluent from the city of Aurora’s wastewater treatment plant for most of its fracking operations, then reuses the water over and over.
“If you put down 10 units of something and only get two back, you have to make up eight units for the next well,” Bracken explained. “We’ll recycle what comes back, add make-up water, put it downhole, recycle what comes back and, eventually, you’re recycling the same molecule of water over and over again.”
Both companies are piping recycled water to and from recycling facilities.
But not all water can be recycled. Sometimes it’s too salty. That’s where injection is most necessary.
“Some of the water is very saline,” Rubinstein said. “Some of the water they’re producing in Oklahoma is … 15 percent salt. Salt is highly corrosive. They really can’t reuse it.”
Though reusing the water is the ideal, there’s simply not enough storage out there to hold the water.
“I guess I’d say there is the ability to now recycle probably 15 to 20 percent of the 100,000 barrels a day coming out of the DJ,” said Josh Patterson, operations director for High Sierra. A third recycling center is in the planning stages.
“Logistically speaking, there wouldn’t be a reservoir large enough to store every barrel (of wastewater) for it to be re-used,” Patterson said.
Costs of recycling are high, but so are trucking costs. If companies can eliminate trucking in new water, and recycle existing water, that takes trucks off the road and reduces those expenses.
Patterson said the demand for water recycling continues to grow, however, with both of High Sierra’s facilities contracted out for the next five years.