Energy-water consortium: Water use in horizontal drilling more efficient than in vertical
February 22, 2012
Extensive water use has been a source of concern as oil and gas companies have gravitated toward horizontal drilling, but drillers can produce much more energy per gallon of water through that technique than with vertical drilling, civil engineers and water experts have discovered so far through studies conducted in Weld County.
Kenneth Carlson, a civil and environmental engineering professor at Colorado State University who serves as a co-director of the Colorado Energy-Water Consortium, said this month that studies conducted by the consortium have also discovered the average amount of water used per completed horizontal well is about 2.8 million gallons – not 5 million gallons of water, which is a commonly used figure.
And though about 400,000 gallons of water is used per vertical well, studies have shown so far the energy returns are much better with horizontal drilling.
“Horizontal drilling requires a lot of water, no doubt … and I think that has caused concerns for a lot of people in this area,” Carlson said. “But if we in fact feel it’s necessary to pull this energy out from the ground beneath us, it looks like horizontal drilling is a more water-efficient way of doing it.”
In its research, the consortium concluded the water use for horizontal wells was about 2.9 gallons of water per million BTUs of energy produced, while vertical wells used 5.4 gallons of water per million BTUs of energy produced.
A million BTUs of energy is the equivalent of about 8.5 gallons of gas, Carlson said.
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All of the 445 wells examined in the study – the majority of which were vertical, as horizontal drilling is still a relatively new technique – used the hydraulic fracturing method. Hydraulic fracturing, or “fracking,” involves blasting water, sand and chemicals into rock formations to free oil and natural gas.
Carlson was in Evans this month talking about the consortium’s ongoing studies, detailing those efforts to attendees of the West Greeley Conservation District’s annual meeting.
Carlson explained at that meeting and in an interview last week that the Colorado Energy-Water Consortium is a public-private partnership between CSU and the oil and gas industry formed about a year ago. It is working to solve issues related to water and the production of oil and gas in Colorado.
The consortium spent the past six months examining 445 of Noble Energy’s wells – all of which are in Weld County, and about 50 of which are horizontal wells. The rest are vertical.
As Carlson explained, the shale formation from which oil is extracted is about 7,000 feet deep underground, but the shale formation itself is relatively shallow – only a few hundred feet deep.
The more commonly used vertical oil wells only go straight down and into the underground shale formation to extract oil, but the technology used in horizontal drilling allows those wells, once they reach the shale formation, to drill horizontally through the shallow shale formation.
Because each individual horizontal well covers more area in the shale formation, the ratio of water used per BTU of energy produced is much less than vertical wells.
Carlson said water-use results may vary, depending on the region where the drilling is taking place, and the companies doing the drilling.
During the meeting in Evans, Carlson also made note of the Colorado Oil and Gas Conservation Commission’s recently published report projecting that from 2010 to 2015 hydraulic fracturing will account for 0.1 percent of the water diverted for beneficial use.
Although the recent water-use studies performed by the Colorado Energy-Water Consortium and the Colorado Oil and Gas Conservation Commission may lay to rest some concerns regarding water use in horizontal drilling, experts spearheading the consortium, including Carlson, acknowledge that horizontal drilling and fracking are not perfect processes, and there is still plenty of research to be done and improvements to be made.
Carlson said there are about 20,000 oil and gas wells in Weld County. Because horizontal drilling looks to be used more often in Weld County and because there are many questions surround the drilling technique, Carlson said he and other water and engineering experts with the consortium will continue with more in-depth research and hope to learn more about the long-term effects of horizontal drilling, as well as fracking techniques.
For instance, he and others with the consortium agree there is potential for better recycling of water in drilling operations, so less water would have to be trucked in.
He also said at the meeting that if oil and gas companies are complying with Colorado Oil and Gas Association rules – regulations that require both a steel pipe and cement casing to serve as barriers between the wells and the surrounding ground and groundwater – the risk of contamination from fracking fluids is low. At the same time, he said, these requirements are self-regulated by the oil and gas companies, and this, too, could be an area of change down the road.
Carlson said he and others also want to further examine the foundation effects of horizontal drilling and fracking.
“I can tell you, many oil and gas companies want to do the right things,” Carlson said. “It just takes research and time to know how this can be done in the most responsible manner.
“Can oil and gas industry do better than it is now? Absolutely. And that’s what we’re working on.”