BBB725
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Ixtoc oil spill lasted June 3, 1979 – March 23, 1980 spilling 3,000,000 barrels of oil into the gulf of Mexico
Ixtoc I was an exploratory oil well in the Bay of Campeche of the Gulf of Mexico, about 100 km (62 mi) northwest of Ciudad del Carmen, Campeche in waters 50 m (160 ft) deep. On 3 June 1979, the well suffered a blowout and is recognized as the second largest oil spill and the largest accidental spill in history.
Mexico's government-owned oil company Pemex (Petróleos Mexicanos) was drilling a 3 km (1.9 mi) deep oil well, when the drilling rig lost drilling mudcirculation. The Ixtoc I was being drilled by the Sedco 135, a semi-submersible platform on lease to Pemex. In modern rotary drilling, mud is circulated down the drill pipe and back up the casing to the surface. The goal is to equalize the pressure through the shaft and to monitor the returning mud for gas. Without the counter-pressure provided by the circulating mud, the pressure in the formation allowed hydrocarbons to fill the well column, blowing out the well. The hydrocarbons caught fire and the platform collapsed.
At the time of the accident Ixtoc was drilling at a depth of about 3,600 metres (11,800 ft) below the seafloor. The day before Ixtoc suffered the blow out and resulting fire that caused her to sink, the drill bit hit a region of soft strata. Subsequently, the circulation of drilling mud was lost resulting in a loss of hydrostatic pressure. Rather than returning to the surface, the drilling mud was escaping into fractures that had formed in the rock at the bottom of the hole. Pemex officials decided to remove the bit, run the drill pipe back into the hole and pump materials down this open-ended drill pipe in an effort to seal off the fractures that were causing the loss of circulation.
During the removal of the pipe the drilling mud suddenly began to flow up towards the surface. Normally, this flow can be stopped by activating shear ramscontained in the blowout preventer (BOP). These rams are designed to sever and seal off the well on the ocean floor, however in this case drill collars had been brought in line with the BOP and the BOP rams were not able to sever the thick steel walls of the drill collars leading to a catastrophic blow out.
The drilling mud was followed by a large quantity of oil and gas at an increasing flow rate. The oil and gas fumes exploded on contact with the operating pump motors, starting a fire which led to the collapse of the drilling tower. The collapse caused damage to underlying well structures. The damage to the well structures led to the release of significant quantities of oil into the ocean.
In the next nine months, experts and divers (including Red Adair) were brought in to contain and cap the oil well. Approximately an average of ten thousand to thirty thousand barrels per day were discharged into the Gulf until it was finally capped on 23 March 1980. Prevailing currents carried the oil towards the Texas coastline. The US government had two months to prepare booms to protect major inlets. Eventually, in the US, 162 miles (261 km) of beaches and 1421 birds were affected by 3,000,000 barrels (480,000 m3) of oil. Mexico rejected US requests to be compensated for cleanup costs.
Ixtoc I was an exploratory oil well in the Bay of Campeche of the Gulf of Mexico, about 100 km (62 mi) northwest of Ciudad del Carmen, Campeche in waters 50 m (160 ft) deep. On 3 June 1979, the well suffered a blowout and is recognized as the second largest oil spill and the largest accidental spill in history.
Mexico's government-owned oil company Pemex (Petróleos Mexicanos) was drilling a 3 km (1.9 mi) deep oil well, when the drilling rig lost drilling mudcirculation. The Ixtoc I was being drilled by the Sedco 135, a semi-submersible platform on lease to Pemex. In modern rotary drilling, mud is circulated down the drill pipe and back up the casing to the surface. The goal is to equalize the pressure through the shaft and to monitor the returning mud for gas. Without the counter-pressure provided by the circulating mud, the pressure in the formation allowed hydrocarbons to fill the well column, blowing out the well. The hydrocarbons caught fire and the platform collapsed.
At the time of the accident Ixtoc was drilling at a depth of about 3,600 metres (11,800 ft) below the seafloor. The day before Ixtoc suffered the blow out and resulting fire that caused her to sink, the drill bit hit a region of soft strata. Subsequently, the circulation of drilling mud was lost resulting in a loss of hydrostatic pressure. Rather than returning to the surface, the drilling mud was escaping into fractures that had formed in the rock at the bottom of the hole. Pemex officials decided to remove the bit, run the drill pipe back into the hole and pump materials down this open-ended drill pipe in an effort to seal off the fractures that were causing the loss of circulation.
During the removal of the pipe the drilling mud suddenly began to flow up towards the surface. Normally, this flow can be stopped by activating shear ramscontained in the blowout preventer (BOP). These rams are designed to sever and seal off the well on the ocean floor, however in this case drill collars had been brought in line with the BOP and the BOP rams were not able to sever the thick steel walls of the drill collars leading to a catastrophic blow out.
The drilling mud was followed by a large quantity of oil and gas at an increasing flow rate. The oil and gas fumes exploded on contact with the operating pump motors, starting a fire which led to the collapse of the drilling tower. The collapse caused damage to underlying well structures. The damage to the well structures led to the release of significant quantities of oil into the ocean.
In the next nine months, experts and divers (including Red Adair) were brought in to contain and cap the oil well. Approximately an average of ten thousand to thirty thousand barrels per day were discharged into the Gulf until it was finally capped on 23 March 1980. Prevailing currents carried the oil towards the Texas coastline. The US government had two months to prepare booms to protect major inlets. Eventually, in the US, 162 miles (261 km) of beaches and 1421 birds were affected by 3,000,000 barrels (480,000 m3) of oil. Mexico rejected US requests to be compensated for cleanup costs.
