Despite producing less wastewater per unit of natural gas produced compared with conventional wells, the enormity of the Marcellus Shale’s growth has increased total wastewater generated in the region by about 570% since 2004, “overwhelming current wastewater disposal infrastructure capacity,” according to a study by researchers at Duke and Kent State universities.

“…[T]he Marcellus shale is massive and the cumulative volume of wastewater generated in the region is growing dramatically,” according to the study, which was published in the journal Water Resources Research.

Hydraulically fractured (fracked) natural gas wells in Pennsylvania’s Marcellus Shale produce “significantly less wastewater per unit gas recovered (35%) compared to conventional natural gas wells,” said researchers Brian Lutz, Aurana Lewis and Martin Doyle. While the average Marcellus well generated six times more drilling waste than the average conventional well during the period studied, they also produced significantly far more gas on average than their conventional counterparts, the researchers said.

“During the first year of production, the average Marcellus well produced 11,180.8 ML [million liters] of gas compared with 198.0 ML in the first year from each conventional well,” they said. “However, the mean annual gas production from Marcellus wells declined rapidly, with only 1,885.2 ML produced in the fourth year of operation.

“On average, conventional wells showed a small but significant increase in gas production during years two and three, but year four was not significantly different from year one. When summed across the four-year period, cumulative mean gas production for a Marcellus well was 30,038.7 ML compared with only 1,050.1 ML from an average conventional well.”

Most wastewater from Marcellus wells is brine generated over multiple years, with only 32.3% classified by operators as flowback from fracking.

The study was based on statewide natural gas and associated wastewater production data for 2000-2011 obtained from the Pennsylvania Department of Environmental Protection’s Bureau of Oil and Gas Management. Waste records for 2007 were not available, the researchers said.

“The first production records for Marcellus wells were recorded in 2004, with the number of new wells each year increasing exponentially, resulting in 2,189 active wells as of December 2011. Typically 3,000-5,000 new conventional wells were added each year since 2004, with 49,294 conventional wells reporting gas production in 2011. There were 3,513 Marcellus well permits issued in 2011, suggesting the number of new Marcellus wells is approaching — and may soon surpass — the rate of conventional well drilling.”

Side by side with all of those new wells will come a staggering increase in wastewater production, the researchers said.

“…[W]e estimate that the wastewater volume from Marcellus wells will exceed 5,370 ML [per year] in 2014, nearly 10 times greater than the volume of wastewater generated by conventional wells a decade earlier and prior to the development of the Marcellus Shale.”

How all of that wastewater will be handled is unclear.

“Because the current wastewater volume generated by only 2,189 active wells threatens to overwhelm existing infrastructure capacity, future development of what is potentially the most important natural gas resource in America’s energy future is likely to become increasingly dependent on novel logistical or technological solutions for wastewater management.

“Not more than a decade ago, extracting natural gas from the Marcellus Shale was commercially unfeasible. Yet technological advances have made unconventional gas production a reality…Advances in unconventional methods for wastewater management, comparable to the advances that facilitated the development of unconventional gas resources, are now needed.”

As drillers compete for access to water for their operations, researchers are looking for new ways to reuse and recycle wastewater for the good of the environment, as well as looking ahead to the possibility of more restrictions at the state or federal level that may be imposed on underground injection wells, according to researchers at consulting firm Accenture (see Shale Daily, Jan. 2).