HOUSTON, Sept 4 (Reuters) - Marathon Petroleum Corp has agreed to be the lead company in 2022 talks with the United Steelworkers union (USW) for a new national agreement covering U.S. refinery and chemical workers, said a USW official.

Marathon, the largest U.S. refiner, will replace Royal Dutch Shell Plc because of changes in the industry over the past decade, said Mike Smith, chair of the USW’s National Oil Bargaining Program.

“Obviously, the industry is in a different place right now than it was a few years ago,” Smith said. “Shell’s position in refining is changing. They’re a smaller presence than they were. Marathon’s position in refining and in our groups is bigger.”

Marathon declined to comment, said spokesman Sid Barth.

Shell has been the lead company in negotiations for the national bargaining agreement, which sets the pay and benefits for 30,000 U.S. refinery and chemical plant workers, since 1997. In the late 1990s, major energy companies like Shell and Exxon operated refineries across the United States.

By 2020, a larger share of refineries in the United States are operated by independent companies like Marathon and Valero Energy Corp. Combined, the refineries operated by those two companies account for 27% of national refining capacity.

The majority of Shell and Exxon's plants are along the U.S. Gulf Coast.

In 2015, talks between the USW and Shell failed to reach an agreement on a contract and more than 7,000 workers at 12 refineries and three chemical plants walked off their jobs for at least two months at most sites and six months at one site.

The longest strike was at Marathon’s Galveston Bay Refinery in Texas City, Texas.

The current contract, agreed to on Jan. 31, 2019, expires just after 12 a.m. local time on Feb. 1, 2022. (Reporting by Erwin Seba; editing by Grant McCool)