The Permian Basin has been a growth engine for the U.S. oil giants in recent years, but as a pandemic-fueled plunge in crude prices forces spending cuts, shale investment has been among the first to go.

Even independent Permian producers, criticized for growing output at all costs, are dramatically altering their plans. Concho Resources Inc. expects to keep production flat this year while warning that it may be forced to curtail some output. The West Texas-based shale explorer has already voluntarily shut in some production.