Oil and gas giants Chevron Corp. (NYSE:CVX), Exxon Mobil Corp. (NYSE:XOM) and Shell Plc (NYSE:SHEL) have evacuated staff and paused operations on oil platforms in the U.S. Gulf Of Mexico ahead of an expected hurricane, Reuters reports. According to the National Hurricane Center, a system developing in the southwestern Gulf of Mexico is expected to grow from a tropical storm and reach hurricane strength on Monday before reaching the northwestern U.S. Gulf Coast by the middle of the week. NHC says the Potential Tropical Cyclone Six was located…