The amount of “produced” wastewater from Marcellus Shale wells being drilled in Pennsylvania has risen dramatically since the development of unconventional drilling began in the early 1990s.
The hydraulic fracturing used to crack the shale layers deep within the earth to allow the gas to flow to the surface requires large amounts of water be injected under very high pressure along with various chemicals and additives. The “produced” water that returns to the surface is a highly salty brine and contains contaminants such as barium, strontium, bromide, and radium, as well as solvents and other chemicals, requiring special treatment and disposal processes.
A study published in the July 2019 edition of Science of the Total Environment took a deep look at waste handling practices and location tracking using Pennsylvania Department of Environmental Protection and federal data, operator websites and Freedom of Information Act records.
The study determined that the amount of wastewater has risen from 3.7 million barrels in 1991 to 57 million barrels in 2017. Among the findings were that the majority of the wastewater produced in Pennsylvania and disposed of in-state, although final endpoints are often not reported in DEP records.
The methods of disposal have changed dramatically since the inception of unconventional drilling. Underground injection disposal wells were used for a large amount of water in the late 1990s, while some was also taken to public sewage treatment plants. However, after plant operators experienced increased amounts of total dissolved solids and bromides in the treated water, state regulators stopped allowing that method.
“The most dramatic of these shifts is the practice of reusing liquid wastes down other production wells primarily for fracturing new wells,” the study states. At the start of unconventional drilling, just 1.4 percent of water was reused, but increased to 69.1 percent in 2013. More than 90 percent of operators in the state reuse water.
“Not only does reuse alleviate the cost of paying for treatment or other expensive options, it also allows operators to purchase less new materials,” the study states. However, it further points out that reuse is only a viable option while new development keeps pace and that lower amounts are reused when there are pauses in drilling.
“The point in time when the wastewater supply from well development and the wastewater demand for new drilling equalize is known in the industry as the ‘crossover point.’ In 2016, that point was reached by some operators. The cost of oil and gas dropped to a point where new well development was no longer economically feasible for some operators and their market for wastewater dropped,” it states.
If they can’t reuse water, operators faced with more expensive wastewater disposal options. At a panel discussion at the recent Shale Insight conference in Pittsburgh, a group of industry experts talked about those options in the current low-price environment as many operators are scaling back drilling.
They attempt to share used water with other operators still drilling, but if that is not an option they must look at temporary storage, centralized treatment plants, disposal facilities or underground injection disposal. New technologies are also being considered to improve the treatment process.
The study noted that a major limitation of the DEP data is that there is no cradle-to-grave tracking system to account for water from the time it is generated until it reaches its final resting place, as just 57 percent of the volume for all years had a distinct listed final endpoint.
“We recommend that PADEP and other oil and gas regulatory agencies nationwide implement a comprehensive cradle-to-grave tracking program, which would provide a much more detailed information on where waste ends up,” the study states. Such data would allow better evaluation of impacts to water and environmental quality and the potential for health risks.
As economic pressures of disposing of wastewater increases, industry groups are once again pushing the Environmental Protection Agency and state agencies to allow disposal of treated water into rivers. The EPA has undertaken a study of wastewater regulations, which is expected to be finalized soon.