Today, the term Big Oil most likely evokes a negative visceral In the maritime industry, a group of six companies that control the chartering of the majority of oil tankers worldwide are together referred to as "Oil Majors". Large petroleum companies began to merge, often in an effort to improve economies of scale , hedge against oil price volatility , and reduce large cash reserves through reinvestment. From Wikipedia, the free encyclopedia. Views Read Edit View history. Acronyms Oil shale gas Peak oil mitigation timing People Petrocurrency Petrodollar recycling Shale band Shale gas Swing producer Unconventional oil heavy crude oil sands oil shale tight oil.