/
Insight

Mexico's Massive IXTOC-I Blowout in 1979

Wed, 01/25/2012 - 17:11

Whilst the Macondo well blowout is certainly the most recent significant oil spill in the minds of the global oil and gas industry, Gulf of Mexico veterans will remember the Ixtoc I oil spill of 1979 as its forerunner in many ways, from the similarities in its causes to its severity and clean up.

IXTOC-1: 3.3 MILLION BARRELS SPILLED INTO THE GULF OF MEXICO

The exploratory well Pemex drilled in 1979 was in the bay of Campeche, some 100km offshore in a 50m water depth. The drilling rig was the Sedco 135-F, owned by a company that later became part of Transocean and built at the Victoria Machinery Depot in British Colombia, Canada. Problems arose when the drilling rig passed the 3,000m mark at the start of June. On June 2nd, the well began to lose drilling mud, and circulation was completely lost at a depth of 3,625m. Following several unsuccessful attempts to regain circulation, Pemex officials decided to remove the drill bit, then run the pipe back into the hole and pump materials down the pipe in order to attempt to seal the fractures that were causing the loss of circulation. On June 3rd, disaster struck. While attempting to remove the drill pipe from the well, mud began to flow up the drill pipe and onto the platform due to the extremely high well pressure.

As a result, the well blew out and caught fire. The explosion and fire destroyed Sedco 135-F, which sank to the sea floor. The well’s stack and casing were damaged in the process and caused oil and gas to mix with water close to the sea floor. Before the Macondo blowout, Ixtoc I was the largest accidental marine oil spill in history: 3.3 million barrels are estimated to have spilled into the Gulf of Mexico.

Some of the techniques used to stop the flow of oil will sound very familiar to those acquainted with BP’s efforts to stop the Macondo well leak in 2010, including attempts to lower a cap onto the well, plug the well with debris, and drill relief wells horizontally through the seabed to stop the flow. Eventually, relief wells managed to halt the flow of oil into the Gulf after months of drilling. The spill occurred in June and July 1979; the wells were pumped with mud, and the flow well was finally capped 290 days later.

Experts generally agree that environmental consequences of the spill would have been much worse had it not been for the fact that the spill occurred in warm waters. Higher water temperatures accelerate evaporation of oil, as well as its weathering and consumption by microbes. Rather than washing up onshore, much of the oil from the Ixtoc I spill remained offshore, either evaporating or settling on the sea bed.