Houston-based Fieldwood Energy LLC and its affiliates are seeking relief under Chapter 11, joining the growing list of U.S. oil and gas operators squeezed by the devastating impact of Covid-19.

The Gulf of Mexico (GOM) giant, a portfolio company of private equity (PE) giant Riverstone Holdings LLC, was formed in 2013. A “comprehensive restructuring” is planned, according to the voluntary petition filed in the U.S. Bankruptcy Court for the Southern District of Texas in Houston.

Fieldwood has the largest footprint of any operator in the shallow Outer Continental Shelf, with stakes in about 500 blocks.

Most of Fieldwood’s exploration and production (E&P) efforts are concentrated in the GOM in water depths of less than 1,000 feet, but it also has deepwater operations and...