Produced water is underground water brought to the surface during the drilling process. Treating and disposing of produced water create an additional expense for oil companies.
One of the most relevant findings from the study is that the most feasible use of produced water generated from the oil and gas industry is for that industry to reuse its own produced water, as opposed to using fresh water.
Robert Sabie Jr., a geographic information systems analyst for NM WRRI, said this cost-effective solution would allow freshwater to be reserved for drinking water. “The focus of the project was to understand the opportunities for reusing treated produced water, both in and out of the oil and gas industry, in order to preserve the freshwater aquifers. Different water uses require different levels of treatment to attain an appropriate water quality. If the produced water is reused within the oil and gas industry, or for other uses with lower water quality standards, then we can use the cleaner, fresh aquifer water for drinking,” Sabie said.
Kenneth “KC” Carroll, an associate professor of water resource management in the NMSU Department of Plant and Environmental Sciences, said the oil and gas industry in West Texas and Southeastern New Mexico produces large amounts of water.
“One of the things we found is that the water produced with oil and gas can be up to 10 times the volume of oil and gas,” Carroll said. “It could be one-to-one, and sometimes no water is produced, but sometimes it’s a lot more.”
With water shortages in the southeastern part of the state, it’s important that researchers identify alternatives to purchasing fresh water from farmers and to reinjecting produced water into the subsurface as a wastewater.
“Southeastern New Mexico is an area that has water shortage issues and a threatened viability of agriculture,” Carroll said. “Although produced water is a wastewater, it is a large source of available water in a region where water scarcity is impacting agriculture.”
Sabie said treatment technology is improving and it is becoming more common for the oil and gas industry to reuse its produced water. It behooves the industry to do so, as there are high costs associated with transporting, treating, and injecting the water into designated injection wells. By reusing their own produced water, companies are able to use less costly and semi-mobile regulated treatment plants closer to the oil and gas extraction areas.
Sabie was the project manager for the feasibility study, and NM WRRI Director Sam Fernald was the principal investigator. NMSU collaborators included Carroll, as well as Pei Xu, an associate professor of environmental engineering in the NMSU Department of Civil Engineering.
“I’m interested in the environmental engineering aspects of produced water,” Xu said. “We need to find an engineering solution to solve the problem. Produced water is such an important topic for the industry, engineering, municipalities, and regulatory agencies. The goal is to treat the water.”
Xu said the feasibility study was made up of a large team, with each person working on a different aspect of the research.
“My job was to investigate the treatment technologies and the cost to treat the water,” she said. “This is an ongoing project. Right now I’m working with Dr. Yanyan Zhang, and we are evaluating the environmental toxicity of the produced water and the level of treatment needed to reduce the toxicity of that water. Our goal is to ensure the safe reuse of that produced water.”
Carroll’s contributions included looking into how the hydrogeologic or geologic formations vary – how deep and which rocks the water comes from – will affect the produced water quality. He also researched the spatial variability of the produced water quality.
“We mapped the salinity of the produced water across most of the Permian Basin at various depths,” Carroll said. “We found that not all produced waters are the same. Water in some areas can have salinity as low as approximately 10 grams per liter, but produced water salinity in some areas can be higher than 350 grams per liter. And seawater average salinity is approximately 35 grams per liter.”
Carroll took the lead on studying the produced water geochemistry, which is the chemical composition of water in the Permian Basin formations that is being pumped to the surface.
“In addition to salinity variations, we found quite a bit of variability in the type of salts dissolved in the waters,” he said. “We also discovered that a significant amount of water migrated deep into the Basin from the land surface, which enhances our understanding of the water flow behavior in deep subsurface basins like the Permian.”
“Our biggest accomplishment was establishing a clearer picture on the regulatory framework,” Sabie said. “There are three state agencies in charge of regulating water – the Office of the State Engineer, the New Mexico Environment Department, and the Oil Conservation Division. So, we got those agencies together and developed hypothetical use cases for produced water to characterize the ownership, jurisdiction agency for New Mexico, holder of liability, and permitting requirements.”