The Ixtoc I oil spill began on June 3, 1979, when an exploratory well drilled by Pemex, Mexico's national oil company, suffered a catastrophic blowout in the Bay of Campeche, Gulf of Mexico. Over the following 290 days, an estimated 140 million gallons (3.3 million barrels) of crude oil poured into the sea before the well was finally capped on March 23, 1980. It remains the largest accidental marine oil spill in recorded history, surpassed only by the deliberate releases during the 1991 Gulf War.
What Caused the Ixtoc I Blowout?
Ixtoc I was drilled by the semi-submersible rig Sedco 135-F under contract to Pemex at a water depth of about 160 feet (49 metres), roughly 100 kilometres southwest of Ciudad del Carmen, Campeche. In early June 1979, the drill bit lost circulation fluid — the heavy drilling mud that counterbalances underground pressure. Without that pressure barrier, highly compressed oil and gas surged up the wellbore in an uncontrolled blowout. The blowout preventer, the last line of mechanical defence, failed to seal the well. Within hours the rig was engulfed in fire and sank, leaving the open wellhead gushing an estimated 10,000 to 30,000 barrels of oil per day directly onto the seafloor at 50 metres depth.
How Did the Spill Spread and Who Did It Affect?
Gulf currents carried the slick northward, contaminating approximately 162 kilometres of Texas coastline by August 1979, reaching Padre Island National Seashore. Mexican beaches along the Campeche and Yucatán coasts were severely fouled. Pemex deployed booms, skimmers, and the chemical dispersant Corexit, and even dropped 100,000 steel, lead, and iron balls into the wellhead in a procedure called 'junk shots' — none proved fully effective. Shrimp and fishing industries on both sides of the border collapsed temporarily; sea turtle nesting beaches were heavily oiled. The U.S. government protested the spill's cross-border impact, but Pemex's sovereign status shielded Mexico from legal liability.
| Spill | Year | Barrels Released | Cause |
|---|---|---|---|
| Ixtoc I | 1979–1980 | 3.3 million | Well blowout (accidental) |
| Deepwater Horizon | 2010 | 4.9 million | Well blowout (accidental) |
| Gulf War spill | 1991 | ~8 million | Deliberate release |
| Atlantic Empress | 1979 | 2.1 million | Tanker collision |
How Was Ixtoc I Finally Capped?
Pemex hired Texas-based oil-well firefighter Red Adair and his team, but the deep subsea location made conventional capping far more difficult than surface blowouts. The primary solution was drilling two relief wells — Ixtoc 1-A and Ixtoc 1-B — that intercepted the original borehole and allowed heavy drilling mud, followed by cement, to be pumped in to kill the well. This process, begun in late 1979, finally succeeded on March 23, 1980, nearly ten months after the blowout started. The disaster directly influenced global offshore drilling regulations and served as a grim preview of the challenges engineers would face again during the 2010 Deepwater Horizon response.
