Too Much Water, Too Few Answers

It could be argued the Permian Basin is a water play with a side of hydrocarbons. While oil is the goal, all that water represents a significant waste stream. Unconventional shale operators fairly quickly started diverting some produced water to hydraulic fracturing, but that still left vast volumes of water to be dealt with. Disposal wells—a favored and economical option—raise a number of potential issues, including induced seismicity. Treatment for reuse faces its own challenges, as does the idea of turning the waste stream into a feedstock for mineral extraction. At the recent Unconventional Resources Technology Conference (URTeC) in Houston, industry experts discussed the problem of produced water, examined the options for dealing with it, presented zero-discharge efforts, and suggested ways to reduce the volume of produced water in the first place. Danny Kingham, principal hydrogeologist at GSI Environmental, noted to a lunchtime URTeC audience that Texas is the largest producer of crude oil, natural gas, and water. The general public may be aware of the first two, she said, but likely does not realize how much water arrives alongside that oil and natural gas. “What they also don’t know is that you get immense volumes of water with that oil and gas. And as you all know, traditionally produced water has been considered a waste stream,” she said. In 2021, she said, the Permian Basin contributed 5.8 million BOPD to the global energy mix, but alongside all that oil, the basin also produced about 24 million BWPD. She attributed the high volume of produced water in the Permian—an area that’s “just been made Swiss cheese with producing wells”—to a trio of factors. “Fields are older, and the older the field is, the more produced water that you’re going to produce with your oil and gas. That’s just a general trend. Also, because of the increase in unconventional oil and gas practices—the horizontal wells with the fracking—that’s going to generate more water. And then significant oil and gas production, we’re just seeing increased oil and gas production in the Permian Basin,” Kingham said. But it’s not just “brown water” coming out of the reservoir, she said. That extremely salty, mineral- and metal-rich water typically contains hydrocarbons, hydrogen sulfides, and naturally occurring radioactive material. Total dissolved solids (TDS) is one measure of water’s purity, or lack thereof. “Fresh water is usually less than 1,000 milligrams (TDS) per liter. Seawater is around 35,000, and most people think the ocean is the saltiest water out there. Most produced water is over 100,000 milligrams per liter,” Kingham said.