One of the key debates in the oil and gas industry across North America is centred on the practice of hydraulic fracturing. This long-established well stimulation technique has drawn attention from the public and media as its ongoing development has brought it into closer contact with populated areas. Concerns regarding contaminated aquifers and increased fresh water use have driven much of the discussion, and governments on both sides of the border are taking a hard look at the practice.
As nearly every oil and gas well drilled today is fractured in some manner, it has become an important tool for operators. With greater scrutiny and regulations being considered or introduced in many jurisdictions, companies using hydraulic fracturing are finding it necessary to look towards more environmentally friendly methods of stimulating wells.
While the core technique isn’t likely to change too much, its components could look quite different moving forward thanks to new developments.
Long-time stimulation tool
While hydraulic fracturing (or ‘fracking’) has only been on the public radar for the past few years, it has been an established practice on oil projects since the 1940s. Mike Dawson, president of the Canadian Society for Unconventional Resources (CSUR), said that the principles of fracking remain similar on today’s well sites.
“The concept was to see what we could do downhole to improve communication, or provide better roadways, from the wellbore into the formation,” Dawson said. “Some formations that have very good reservoir properties don’t need much stimulation at all, but expanding our exploration area, we find that other rocks contain oil and gas but need a bit of a kickstart to get it flowing.”
Hydraulic fracturing is a simple process at its core: once the wellbore is drilled to the required depth and resource-bearing formations identified, small explosive devices are used to blast openings into the rock of the formation. Fracturing fluid, a mixture of chemicals and proppant (usually sand), is pumped down the hole at extremely high pressure, forcing the formation to crack and creating an easier route for oil or gas to flow into the well.
The oil industry has used fracturing more and more over time as exploration has turned up tighter deposits of hydrocarbons.
“The low-hanging fruit of those very easy reservoirs where stimulations weren’t necessary have gone by,” Dawson said. “If you plotted the production from conventional wells versus unconventional wells, you’d see a very significant trend – as conventional decreased, you will see an increase in hydraulic fracturing.”
As the industry has matured and more unconventional reserves have been tapped, fracking has seen changes in its technology. Pumping equipment has increased in its size and effectiveness, frac fluid has evolved, and – perhaps the biggest change – downhole work has improved with the development of horizontal drilling and borehole isolation allowing multi-stage fracturing operations.
“As companies have changed their technology more towards horizontal drilling, we’ve seen fracturing change as well to be more effective in terms of stimulation of these horizontal wells,” Dawson said.
Multi-stage fracturing is integral to the use of horizontal drilling, he noted. While a vertical well might bore through a 15-metre segment of hydrocarbon-bearing sandstone, a horizontal well can extend hundreds or thousands of metres through the formation. Borehole isolation techniques that allow short segments of the well to be fractured at a time are ideal for taking advantage of that long segment of pay well.
Downhole monitoring is also a greatly improved sector, Dawson noted. Instead of earlier fracturing methods that revolved around pushing fluid down the hole and hoping for the best, today’s fracturing operations have a far greater view of what’s happening in the formation.
“With advanced technology, operators can design a frac job and modify it on the fly,” he said. “They can measure what’s going on downhole in terms of pressure and microseismic events, tailor and adjust it as they go along. In some cases, that can even be done from head office.”
Refinements in all areas
Drilling companies themselves are constantly working to improve their fracturing operations, keeping public concerns in mind as they move forward. The work is a combination of improving the existing techniques and educating the public about how those improvements change the process for the better.
“I talk to people every single day who think I’m lying saying that fracking is safe, that it’s not something we invented two years ago,” explained Chris Faulkner, CEO of Breitling Oil & Gas. “They believe what they read, and what they read is inaccurate. There’s a lot more to clearing that up than just saying ‘you’re wrong and we’re right’.”
Breitling has a substantial portfolio of fracking operations, and much like many companies is searching for answers to public concerns.
Water use and protection is one of the key concerns expressed by the public, so recycling and closed loop fracturing are important steps for his company, Faulkner said.
“Water acquisition is the big argument in the U.S.… we’re not where we want to be yet and still have to reintroduce fresh water, but we are recycling our chemicals and we’re reducing our environmental impact using pad drilling,” he said. “There are a lot of up-front costs... but once you get past those, if you’re doing pad drilling and not moving your rigs around, having everything already there makes the most sense.”
Pad drilling – using horizontal drilling to bore multiple wells from the same location – and on-site recycling are slowly growing in popularity among the industry, Faulkner said. They also open the doors to more opportunities such as closed loop fracking.
“On-site, we have a blender in which we mix sand, chemical and water, and that’s pushed down the hole. When it comes back up, we capture that fluid, and instead of putting it into a reserve pit we flow it into a steel frac tank,” he said. “We capture the fluid and use a filtration process to remove partially dissolved solids, which are disposed of in a wastewater treatment facility safely. Then we reinject water into the fluid and reuse it in the fracturing process.”
Closed loop fracturing means less water is used, there is far less likelihood of fluids leaching down into the aquifer – Faulkner noted that most fracturing operations are done far below the aquifer, so water leaching down from the surface is the most likely potential contamination source – and there is less traffic in terms of trucks moving in and out of the site with fluid and chemical.
The future holds changes to fracturing fluids to reduce the potential hazards to the water table. Breitling has been working to develop a frac fluid using food-safe fluids rather than harsh chemicals, and is currently testing their new cocktail in tight gas wells.
“We’ll remove those harmful chemicals within 12 months, we’ll recycle water within 36 months, and I think perhaps sooner than that we’ll have some sort of waterless fracking system that works with most geologies,” Faulkner noted.
While companies and associations are working to answer public concerns, regulators are also giving the technique a look. In Canada, the Quebec government has instituted a moratorium on fracturing as studies are performed, and other provinces have instituted opt-in registration systems for frac fluid chemicals. The Canadian Association of Petroleum Producers has instituted a set of guidelines for companies drilling and fracking gas wells.
The United States has seen more focused regulatory activity. On May 4, the Department of the Interior introduced a proposal requiring companies to publicly disclose the chemicals used in their frac fluid. The rule also requires companies to improve their assurances that wellbore integrity is such that fluids are not able to escape during fracturing operations, and to confirm that a water management plan is in place for flowback fluids.
While environmental concerns are being addressed, the jury is still out on a final issue surrounding hydraulic fracturing – whether there is a link between the practice and increased earthquakes. Two studies released recently in the U.S. and UK suggested that deep-well injection of treated water may have been associated with small earthquakes.
“Induced earthquakes have been known of for about 100 years and are very common around underground mining operations, including here in Canada,” noted Kevin Heffernan, CSUR vice-president. “The fact that breaking rocks with hydraulic fracturing creates measurable seismic events shouldn’t surprise anybody.”
Issues such as earthquakes and incidents of damaged aquifers near fracturing operations get higher visibility than the industry’s protective efforts, Faulkner noted. Public education is important for breaking those negative perceptions.
“The industry is late to the party. People have already made up their minds, and we have to convert those naysayers to our side. The reality is that will be very difficult, as their concerns are clearly set forth,” he said. “But, if we’re going to continue to freely access the reserves that are deep within the earth that need fracturing to unlock, we have to be able to do it.”