LOS ANGELES—When students in Jamie Rector’s Energy and Civilization course at the University of California, Berkeley, came to him with the idea for a project on California’s abandoned oil wells, he was intrigued.

The state has more than 120,000 abandoned oil and gas wells, as well as 30,000 idle and 70,000 active wells. Many were drilled or dug in the late 1800s, clustered in areas such as downtown Los Angeles and near present-day Dodger Stadium, where the California oil boom began.