An unconventional frac job requires 5 million gal of water on average. About 50-80% of this amount will flow back to surface within the first few weeks of production. In many cases, this flowback is being treated and reused on subsequent wells. Where commercial disposal wells are available, produced water is often reinjected at a lower cost than recycling. Dry fracing, or waterless fracing, may soon take water out of the equation for some operators.
Obtaining fresh water can be problematic in arid regions such as in South Texas, a region prone to drought. In other regions, such as Pennsylvania's Marcellus shale, disposing of water through deep well injection is extremely limited. Operators typically recycle and reuse water or transport via truck to disposal wells in Ohio.
According to a study published by World Resources Institute, nearly 47% of all unconventional wells are located in areas with high or extremely high baseline water stress. Limited supply and risks of contamination will translate into technological advancement within the next few years. Recycling and reuse technology is already used in many North American plays, but newer methods may remove water from the equation.
Closing the loop
Industry problems are often addressed through technological solutions. Calgary-based GasFrac Energy Services Inc. developed its closed-loop stimulation process in 2008, which uses a propane-butane gel to produce hydraulic fractures in horizontal wells. The company has used the process in more than 2,000 completions in 758 locations in Canada and the US.
The waterless system has recently made headway in the Eagle Ford shale of South Texas. The company has opened a base in Floresville, Tex., and its system is improving production for some operators. San Antonio-based BlackBrush Oil & Gas LP has announced its success in using the technology to avoid finding and managing access to freshwater in its Eagle Ford operations. To date, the companies have completed 20 wells using gas in place of water with a 100% increase in initial production.
"It has to be applied to the right well," explained Eric Tudor, spokesman for GasFrac. Deeper wells can be problematic as gas can prove more difficult to pressurize downhole.
"Using hydrocarbons to fracture these wells, which tend to be under-saturated, is ideal," Tudor said. "The clay effectively optimizes completion as the gas does not react with clay. Effective frac lengths turn out to be longer than those created with water." Ultimately, this enables higher initial and long-term production.
The LPG gel properties include low surface tension, low viscosity, and low density, along with solubility within naturally occurring reservoir hydrocarbons. The system also has the ability to evenly distribute proppant with the gelled slurry during pumping, which decreases the chance of proppant settling within the formation. The gel regains permeability with the stimulated hydrocarbons, allowing 100% recovery within the early phase of production.
|GasFrac first deployed its system in 2008. This was the company's first "dual crew" project completed on the Cardium and Falher formations in the Edson, Alta., Canada area.|
One risk associated with the process is the use of flammable natural gas. "The system is completely closed-loop," Tudor said, adding, "The industry is well-versed in handling flammable liquids safely."
Using flammable material in hydraulic fracturing has raised some skepticism. Unrelated to this system, Houston-based eCORP Stimulation Technologies LLC reported in April that it plans to develop a system to render liquid propane as a nonflammable stimulation fluid. Should the system work, it could dramatically widen the application of waterless fracing throughout North America.
From an atmospheric standpoint, propane, butane, and pentane are not greenhouse gases. With relatively short atmospheric lifetimes, there are no essential concerns drawn from fracing with gas as opposed to water.
Geographically, South Texas is well-suited for the outgrowth of waterless fracing. Propane used for the process is supplied from Corpus Christi, Tex., on the Gulf Coast. For the Eagle Ford shale, this ample supply of gas ensures seamless activity with no real pressure on demand. While the company's Eagle Ford operations are well supplied, moving to liquids from the field is most likely a natural evolution for the process. "With a big enough project, using liquids-rich gas may become feasible in time," Tudor said. "Onsite recycling of natural gas is a ‘next step' as the technology is advanced."
In 2012, fewer than 5% of wells stimulated in the US used fluids other than water. As recycling technology advances, and waterless fracing continues to spread, more water may be left at its source in the coming years. While water can be considered an ample—yet finite—resource, the landscape for its open use is continually evolving, particularly where unconventional development is concerned. According to Tudor, "Freshwater may not be used in the same way 10 years from now." And water management may not be an issue for unconventional resource developers within the next decade.