Alternatives to reinjecting produced water will be essential not only to avoid induced seismicity but also to provide an additional source of water for energy operations, a speaker suggested during a breakout session at the US Energy Information Administration’s 2017 conference.
“We’re in an arid period—about 100 years into a 300-year cycle,” said Linda Capuano, an energy technology fellow at Rice University’s Baker Institute for Energy Studies. US states project economic growth will require using water from nontraditional sources, including the brackish water associated with oil and gas production, she noted during the June 26 discussion.
The good news, Capuano said, is that produced water requires less treatment than other alternatives to fresh water because it contains below 30,000 ppm of dissolved solids in some cases. “It also is found in arid states where it is needed most,” Capuano said.
Growing use of renewable technologies will not reduce requirements for water to generate electricity, Capuano warned. “As the oil and gas industry depends more on treated produced water to operate, states will have to prepare for instances where it is not immediately available, putting more pressure on surface water supplies,” she said.
“Rapid analytical and purification testing techniques are needed. Treatments will need to fit specific purposes. We need to identify other key variables besides produced solids. More states need to rigorously account for produced water because the oil and gas industry is using it more,” Capuano said. “Produced water is here, and it’s available. We need to learn how to use it more efficiently.”
Two Oklahoma Geological Survey (OGS) officials, meanwhile, said that more information about each area’s characteristics will be needed for states to develop sound strategies to avoid induced seismic events. “Right now, the earthquake trend in our state is flattening somewhat, but it’s still more than most people like,” observed OGS Director Jeremy Boak. Reduced production in response to plunging oil and gas prices primarily drove the decline, he added.
Stress vs. strain
“There are other induced seismicity causes besides wastewater injection. But in all cases, it involves stress vs. strain,” said OGS hydrologist Kyle E. Murray. “What we know is based on very limited data. The further back in time we go, the less reliable it becomes.”
It is becoming apparent, however, that solutions that would work in Oklahoma would not necessarily apply in North Dakota or Pennsylvania, Murray said. OGS is working with the Texas Bureau of Economic Geology to determine quake frequencies in the Bakken, Barnett, and Eagle Ford shales, Murray said. “Depth relative to basement is important. Oklahoma wells are deeper than the ones in Pennsylvania, so pressure is harder to measure.”
Murray said, “Operators in Texas dispose of water in wells that are shallower than in Oklahoma, which avoids seismicity problems but raises potential problems with drinking water and other supplies. There is a value we can assign to water as an economic asset. How we treat it matters.”
Capuano added, “States with a lot of water, particularly in the Northeast, don’t manage it as aggressively as states which don’t have as much. The Groundwater Protection Council is working to help improve this.” State agencies, she added, are working with producers to better protect nearby communities from induced quakes.
It’s always interesting when there’s a correlation between activities and impacts, Capuano said. “Ten years ago, the biggest concern was crude oil production’s possible impacts on drinking water supplies. We’re largely past that now because it has been determined that defective wells pose the greatest threat, and these can be avoided with the appropriate effort,” she said.
Other misconceptions need to be cleared up, Boak said. “There’s one that disposal wells involve high pressure, similar to hydraulic fracturing. That’s not the case. Most involve water that’s simply poured into the formation from the surface,” he said.
Contact Nick Snow at firstname.lastname@example.org.