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Potential of produced water to fill California supply gap

Changing conditions in California could provide an opening for treated produced water to meet shortfalls in traditional water supplies.

California could be facing a severe water supply-demand gap in the coming years as urbanization rates climb and the local agriculture industry increasingly moves towards crops requiring year-round irrigation. Central to both the state’s agriculture and oil & gas industries is Kern County, which alone is set to experience a shortfall of about 900,000 acre feet (6.98 billion bbl) per year by 2040, Aquilogic CEO and principal hydrologist Anthony Brown told attendees of the Produced Water Society’s 30th annual seminar.

A factor that will exacerbate the situation is California’s recently adopted Sustainable Groundwater Management Act (SGMA), which will limit volumes available to water users and subsequently lead to higher water prices. “Groundwater pumping right now is projected to have to decrease in Kern County by about 40% over the next 20 years,” Brown said. “That is a best-case scenario. I think it realistically might be closer to 60%.”

At the same time, California is confronting another challenge: what to do with its increasing volumes of produced water, especially at a time when disposal options have become more constrained. While 2017 statewide water-to-oil ratios (WORs) averaged 20:1, some of Kern County’s mature oilfields saw WORs as high as 50:1, with total produced water volumes reaching around 1.8 billion bbl that year.

California’s last evaporation pits were shuttered in 2019, so operators can only dispose of produced water via saltwater disposal wells (SWDs), a practice which itself faces limitations related to injection depths and pressures. This has driven up water management costs.

“In general, produced water [disposal] costs have – up until last year – generally run at about $0.20-0.25/bbl,” Brown told the audience. “With the closure of the pits, we could be looking at costs over the coming year that are more in the range of $0.40-0.70/bbl.” This threatens to “become the biggest limiting factor on oil production” in the state, he added.

Treating produced water for beneficial reuse could help relieve water stress. A number of applications exist for the water, though the one requiring the least treatment would be irrigating crops to feed livestock.

Aquilogic is currently conducting a feasibility study for a phased project that would reuse water produced from the California Resource Corporation-operated Mt. Poso field, which in 2017 produced about 25.3 million bbl of water for only 1.5 million bbl of oil. The project’s first phase envisions delivering about 4,000 acre feet (31 million bbl) per year of water via pipeline for agricultural beneficial reuse in the Kern-Tulare Water Districts. An additional 6,000 acre feet (46.6 million bbl) per year would be provided for regional use during phase two.

Brown believes the cost of produced water treatment for beneficial reuse will eventually dip below reinjection costs. “Now is the time to start planning for that if you believe that in 3-5 years it might be economically viable to make use of this produced water for off-field beneficial use,” he urged the audience.

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