Tayvis Dunnahoe
Special Projects*
Water resources are an important factor in unconventional oil and gas development. At both ends of the barrel, water is a necessary component of developing gas and oil and, once spent, produced water must be handled and disposed of properly.
Dry fracing, or waterless fracing, may soon take water out of the equation for some operators. While the amount of water used to frac a well varies by play, most shale completions will require an average of 5 million gal. 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.
In South Texas, a region prone to drought, the dual issues of water consumption and disposal have made headlines in recent months. Last year, shale production consumed 25 billion gal of water statewide. Compared with competing interests such as agricultural irrigation, manufacturing, and power generation, this amounts to a small percentage of the total statewide consumption.
Water usage is a regional issue. For many South Texas communities, such as Barnhart where local supplies have nearly dissipated in recent months, increases in water demand can have a profound effect on local supplies. While the industry has come under recent focus because of local water shortages in the heart of the Eagle Ford shale, it is important to note that nearly 90% of the state has been under severe drought conditions through much of this year according to the Texas Water Development board.
Waterless fracing advancements
Like most problems associated with oil and gas development, technology may soon provide a clear solution to water shortages in arid regions. GasFrac Energy Services Inc., Calgary, developed its closed-loop stimulation process in 2008, which uses a liquified petroleum gas (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 area of South Texas. The company has opened a base in Floresville, Tex., and its system is actually improving production for some operators.
BlackBrush Oil & Gas LP, San Antonio, 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," said Eric Tudor, spokesman for GasFrac.
Some critics of the technology suggest that deeper wells can be problematic as gas can prove more difficult to pressurize downhole, but in reality propane and butane will remain in a viscosified liquid form allowing for a wide range of application.
GasFrac has successfully treated wells to a true vertical depth of 13,000 ft with bottom hole temperatures approaching 300° F.
"Using hydrocarbons to fracture these wells, which tend to be undersaturated in respect to water, i.e. wells that do not produce water naturally, is ideal," Tudor said.
"The damaging effects of clay swelling in the formation are effectively eliminated during the completion as the LPG (propane and butane) does not react with clay," Tudor said, adding, "Effective frac lengths turn out to be longer than those created with water." Ultimately, this enables higher initial and long-term production of the well.
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 thereby allowing 100% recovery within the early phase of production.
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."
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. While this technology is also in its early phase, there could likely be developments that further improve on waterless fracing.
Environmental standpoint
From an environmental 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 refined LPG 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 LPG 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."
*Tayvis Dunnohoe is editor of OGJ's Unconventional Oil & Gas Report.
