By Kevin Westerling,
Are you for or against it? It seems everyone has picked a side in the debate over hydraulic fracturing (“fracking”), but most conflict would likely fall away if fracking was performed in a proven safe and sustainable manner, verified by a reliable source.
There are multiple issues that concern those opposed, including the potential for aquifer contamination during the process and pollution from wastewater, or “produced water,” coming out of the process. A third concern is the sheer volume of water required within fracking operations, especially in water-scarce areas. While debate will continue on the first two issues — not tackled within this article — the U.S. Government Accountability Office (GAO) has studied and reported on water-efficient fracking techniques that are proven and reliable.
GAO’s Water in the Energy Sector technical assessment was delivered to Congress (by request) in August and made publicly available in September. According to GAO Chief Scientist Timothy M. Peters, the report “examine[s] the current state of technologies that are either available or being developed to reduce freshwater consumption or that employ alternative water sources [i.e., treatment, recycle, and reuse] in hydraulic fracturing…”
In addition to providing technology information, the report addresses the underlying need for such technologies. A number of shale gas and shale oil plays are located in dry, drought-prone areas — namely Barnett in central Texas, Niobrara in Nebraska, and Bakken in North Dakota. GAO cites an oft-referenced report from 2012 (by Jean- Philippe Nicot and Bridget R. Scanlon) indicating that fracking activities in Texas accounted for less than 1 percent of statewide water withdrawals. True enough, but the same report reveals a much greater impact at the local level — as much as 29 percent of annual net use for some counties. GAO adds that fracking and related water needs are still growing; a GAO study from September 2012 revealed a five-fold increase in activity from 2007 to 2011, and the Colorado Oil and Gas Conservation Commission, through a May 2014 study, projected a 35-percent increase in annual water demand for Colorado’s fracking between 2010 and 2015.
To put real numbers to the water use, yet another GAO-cited report estimates that each well consumes between 2 and 9 million gallons, with the high fluctuation due to differing shale geology and fracking processes.
But how about processes that use little to no water? Here are three to consider.
Liquefied Petroleum Gas (LPG) Fracturing
In conventional hydraulic fracturing, “fracking fluid” is injected into a well at high pressure to pierce the shale and release the oil or gas. Mostly comprised of water, fracking fluid also contains proppants — typically sand or man-made materials designed to hold the hydraulic fracture open to facilitate oil/gas recovery. LPG fracturing essentially replaces the water in the fracking fluid with, traditionally, nitrogen or carbon dioxide (CO2), and more recently with a mixture of propane and chemical additives. This gas-based process has advantages over water for certain shale formations — those that exhibit low permeability and require low-pressure fracturing. Water-based fracking inhibits flow out of the wellbore, whereas gas-based (LPG) fracking, with its lower viscosity and density, promotes flow out of the formation; plus, there is no need to recover and treat injected water. The technique has been proven more efficient than water-based fracking with certain plays in Canada and Texas, but it also has drawbacks.
LPG-based fracturing is limited to specific shale formations, and even then there are concerns over its relatively short track record, as well as safety and cost — propane is both flammable and expensive. For the right application, however, and especially when infrastructure that allows the propane to be captured and reused is in place, LPG can increase oil and gas production while saving water.
In foam-based fracturing, the fracking fluid is composed of a small amount of water, a foaming agent, and nitrogen or CO2. Again, the technique was designed to overcome specific obstacles to efficient shale gas production — in this case, low-pressure, water-scarce formations where reservoir pressure is too low to drive water and gas out of the well. Cited in the GAO report, the National Energy Technology Laboratory (NETL) found the technique, when used by the Department of Energy (DOE) to stimulate Devonian Shale wells in the eastern U.S. during the 1970s, reduced water usage by 75 to 90 percent versus “slickwater” (conventional) fracking.
Unfortunately for the fate of process — and water conservation — the success could not be duplicated when applied to formations that typically require high pressure and high volumes of water. When Mitchell Energy pitted foam-based fracturing against slickwater fracking at the Barnett Shale in Texas, the latter recovered as much or more gas at half the cost. Foam-based fracturing has since fallen out of favor, notes GAO, but rising water-scarcity concerns have renewed the interest of researchers; its efficacy and financial viability will be reexamined now that water restrictions and treatment regulations related to slickwater fracking are becoming increasingly prevalent.
Channel Fracturing Technology
Relative to other alternatives to conventional fracking, channel fracturing has the most potential for the immediate ability to conserve water, due to its widespread use and effectiveness. The technology is based on the behavior and manipulation of proppants, which are injected into the formation with fluid and then coaxed into clusters by a proppant-free gel that is also injected. The cluster placement, as shown in the figure below (image and caption credit: Schlumberger/GAO), allows gas to flow more freely, enhancing production by as much as 60 percent (during one Eagle Ford Shale study) and reducing water consumption by 58 percent (per a separate Eagle Ford study). The technique is also said to reduce operational costs and safety and environmental risks, according to GAO. Channel fracturing has been widely adopted — used in major shale plays throughout the U.S., as well as overseas — but must still be proven “over a sufficiently long time span [and] across different types of shale plays...” to some industry insiders interviewed by GAO for the report.
Flow channel creation with channel fracturing technology
Source: Schlumberger | GAO-15-545
Left image: Proppant media placement typical of conventional hydraulic fracturing. Hydrocarbons flow through the homogeneously-placed proppant.
Right image: Hydrocarbon flow patterns created by a channel fracturing technique create open channels through which hydrocarbons can flow more easily.
A key lesson notable from an examination of these water-saving alternatives to fracking and their potential impact is that water conservation, per se, is not the key to the equation at all — at least not to oil and gas companies. Rather, increased production at less cost will dictate the adoption rate of these technologies, with water savings simply serving as a happy byproduct.
However it happens, we’ll take it.