An exploratory oil well being drilled by the semi-submersible drilling rig Sedco 135 in the Bay of Campeche of the Gulf of Mexico.
Mexico’s state-owned oil company Pemex was drilling a 3 km deep oil well when on 3 June 1979 the drilling rig Sedco 135 lost drilling mud circulation that resulted in the destruction and sinking of the rig.
In the initial stages of the spill, an estimated 30,000 barrels of oil per day were flowing from the well. In July 1979, the pumping of mud into the well reduced the flow to 20,000 barrels per day, and early in August the pumping of nearly 100,000 steel, iron, and lead balls into the well reduced the flow to 10,000 barrels per day.
Pemex claimed that half of the released oil burned when it reached the surface, a third of it evaporated, and the rest was contained or dispersed. In total, around 138,500,000 US gallons of oil and 3.3 million barrels of oil were spilled throughout the roughly, 10 months it took for the oil to stop leaking.