Fracked Wells Team Up with Energy Storage

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The innovation

REFRAES (REpurposed FRAcked wells for Energy Storage)

The big picture

REFRAES has the potential to provide long-term, scalable energy storage.

The players

National Renewable Energy Laboratory (NREL) researchers Chad Augustine and David Young, along with former NREL colleague and Henry Johnston, a veteran of the oil and gas industry.

Computer modeling done by scientists at NREL and Colorado School of Mines has confirmed the feasibility of the idea. The researchers published two papers detailing their work late last year and were awarded a patent protecting the process.

A conceptual schematic of the energy storage system using old wells for energy storage. Illustration by Al Hicks, NREL

How it works

The technology uses depleted oil and gas wells as a reservoir for the storage of compressed natural gas. The gas can be released as needed to spin a turbine and generate electricity. The reservoir is recharged using excess electricity from the grid and the cycle repeats, providing a potential solution for the growing demand for energy storage, according to NREL.

The technology calls for a four-phase process, with the gas first injected into the reservoir at a constant flowing bottomhole pressure to store energy. The well is then shut in so that the gas cannot escape. Next, the gas is produced from the reservoir at a constant pressure to generate electricity. Finally, there is a recovery period during which the well is again shut in.

After the recovery period, the storage cycle is repeated.

Utilizing depleted oil and natural gas wells takes advantage of the growing number of horizontal, hydraulically fractured, or “fracked,” wells. The technique, which accounts for the majority of all newly drilled wells in the U.S., drills down and then straight across through the rock. Water is then pumped into the well at high pressure to fracture the shale to free trapped oil and natural gas.

Why it matters

The process can provide six hours of electricity for shorter-term needs, and 90 days of electricity for longer-term, seasonal needs.

While the researchers have chosen to launch the program with natural gas due to its availability and ease in getting well owners on board with the idea, the plan could gradually shift over to a different gas to run the system. This includes CO2, nitrogen, and hydrogen. Using CO2 could also be part of a carbon capture cycle, according to NREL.

Next Steps

The NREL researchers are working on a pilot project to demonstrate the technology.

The Department of Energy’s Geothermal Technologies Office, which funded the research conducted by Augustine and his colleagues, is separately investing in the possible use of inactive wells for geothermal energy.

Stay tuned for the next installment of the Energy Edge Innovation Series!