Transforming old oil wells into energy storage assets

‘Gravity wells’ could provide the grid with cheap energy storage services

Spotted: There are more than 2.6 million inactive oil wells in the US and Canada, according to US startup Renewell. These present a significant environmental hazard, leaking the potent greenhouse gas methane as well as other air and soil pollutants. But cleaning and plugging all these legacy wells is very expensive, and there is little incentive for companies to take on the task.

Now, however, the Texas-based company has an alternative solution: turning disused wells into cheap sources of energy storage. The company retrofits wells that have an existing grid connection with a gravity-based mechatronic energy conversion system. This stores and then discharges energy by raising and lowering a long cylindrical weight in the existing wellbore. When there is an excess of energy on the grid, the weight is lifted. Then, when there is high energy demand the weight is dropped, and a high-efficiency motor converts its mechanical energy to electricity. An intelligent control platform allows the system to be monitored and controlled remotely.

The weight itself is made from old oilfield materials and equipment, such as tubing and high-density filling, and the system takes advantage of other existing infrastructure located at oil wells, such as pumpjacks, communications networks, and roads. The well is also plugged above the depleted reservoir and the well is monitored by a suite of sensors. This is an improvement on the minimum requirements set by state-based regulations, which typically only require oil and gas companies to plug and abandon old wells, with no obligation to monitor their status.

Renewell will generate revenue from the energy storage services it sells to the grid for a period of 30 years, and the startup will share a proportion of this revenue with the well owner as a form of rent.

Springwise has previously spotted another mechatronic system making use of old coal mine shafts. We have also seen a startup using microbes to generate hydrogen from depleted oil reserves.

Written By: Matthew Hempstead