Chevron said it would buy Hess in an all-stock deal worth $53 billion, the second major oil tie-up this month following Exxon Mobil’s deal to buy Pioneer Natural Resources.

The U.S. energy company said buying Hess would upgrade and diversify its portfolio, marking Chevron’s entrance into an Exxon-led partnership overseeing a generational oil find in Guyana, while picking up additional U.S. shale assets largely in North Dakota. Chevron also highlighted the attraction of Hess’s assets in the Gulf of Mexico and its natural-gas business in Southeast Asia.