The impairment is a sign that the waters are getting pretty rough for the oil and gas industry, due to a combination of supply surpluses, low prices, the struggling and unproven business case for large-scale shale drilling, and the looming threat of peak demand.

The write down comes as Chevron lowered its long-term forecast for oil and gas prices, which directly impacted the value of its assets. "We have to make the tough choices to high-grade our portfolio and invest in the highest-return projects in the world we see ahead of us, and that's a different world than the one that lies behind us," Chevron Chief Executive Mike Wirth said in an interview with the Wall Street Journal.

The WSJ says the admission that billions of dollars' worth of assets are worth a lot less than previously thought could force others to "publicly reassess the value of their holdings in the face of a global supply glut and growing investor concerns about the long-term future of fossil fuels."