One of America’s wealthiest businessmen is embroiled in a nasty divorce that could spark the biggest divorce settlement in U.S. history.

Harold Hamm, chief executive of oil giant Continental Resources, is facing losing a large portion of his $11.3 billion fortune to his estranged wife Sue Ann Hamm who filed for divorce, alleging that her husband “was having an affair” in 2010, court papers obtained by Reuters say.

The pair married in April 1988 and have two children, Jane and Hilary. Harold, 67, has three children from a prior marriage that ended in divorce in 1987.

In the new sealed docs, filed on March 7, it’s unclear if a prenuptial agreement was ever signed. But if there