Ixtoc I
Encyclopedia
Ixtoc I was an exploratory oil well being drilled by the semi-submersible
drilling rig
Sedco 135-F in the Bay of Campeche
of the Gulf of Mexico, about 100 km (62.1 mi) northwest of Ciudad del Carmen
, Campeche
in waters 50 m (164 ft) deep. On 3 June 1979, the well suffered a blowout
resulting in one of largest oil spills in history.
(Petróleos Mexicanos) was drilling a 3 km (1.9 mi) deep oil well
when the drilling rig
Sedco 135F lost drilling mud circulation.
In modern rotary drilling, mud is circulated down the drill pipe
and back up the well bore 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 oil to fill the well column, blowing out the well. The oil caught fire, and Sedco 135F burned and collapsed into the sea.
At the time of the accident Sedco 135F was drilling at a depth of about 3600 metres (11,811 ft) below the seafloor. The day before Ixtoc suffered the blowout 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 on Sedco 135F, the drilling mud suddenly began to flow up towards the surface; by removing the drill-string the well was swabbed leading to a kick. Normally, this flow can be stopped by activating shear rams contained in the blowout preventer
(BOP). These rams are designed to sever and seal off the well on the ocean floor; however in this case the 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 blowout.
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 Sedco 135F 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 Gulf.
nearly 100,000 steel, iron, and lead balls into the well reduced the flow to 10000 barrels (1,589.9 m³) 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. Mexican authorities also drilled two relief wells into the main well to lower the pressure of the blowout, however the oil continued to flow for three months following the completion of the first relief well.
Pemex contracted Conair Aviation to spray the chemical dispersant Corexit
9527 on the oil. A total of 493 aerial missions were flown, treating 1100 square miles (2,849 km²) of oil slick. Dispersants were not used in the U.S. area of the spill because of the dispersant's inability to treat weathered oil. Eventually the on-scene coordinator
(OSC) requested that Mexico stop using dispersants north of 25°N.
In Texas, an emphasis was placed on coastal countermeasures protecting the bays and lagoons formed by the barrier islands. Impacts of oil to the barrier island beaches were ranked as second in importance to protecting inlets to the bays and lagoons. This was done with the placement of skimmers and booms. Efforts were concentrated on the Brazos-Santiago Pass, Port Mansfield Channel, Aransas Pass, and Cedar Bayou which during the course of the spill was sealed with sand. Economically and environmentally sensitive barrier island beaches were cleaned daily. Laborers used rakes and shovels to clean beaches rather than heavier equipment which removed too much sand. Ultimately, 71500 barrels (11,367.6 m³) of oil impacted 162 miles (260.7 km) of U.S. beaches, and over 10000 cubic yards (7,645.5 m³) of oiled material were removed.
were brought in to contain and cap the oil well. An average of approximately 10000 to 30000 bbl (1,589.9 to 4,769.6 m3) per day were discharged into the Gulf until it was finally capped on 23 March 1980, nearly 10 months later. In similarity to the Deepwater Horizon oil spill
31 years later, the list of methods attempted to remediate the leak included lowering a cap over the well, plugging the leak with mud and "junk", use of huge quantities of dispersants, and spending months attempting to drill relief wells.
as a state-run company.
The oil slick surrounded Rancho Nuevo, in the Mexican state of Tamaulipas
, which is one of the few nesting sites for Kemp's Ridley
sea turtle
s. Thousands of baby sea turtles were airlifted to a clean portion of the Gulf of Mexico to help save the rare species.
The oil on Mexican beaches that the authors observed in early September was calculated to be about 6000 metric tons. Based on reports from various groups and individuals, five times that figure is thought to represent a fair estimate of what had landed on Mexican beaches. Investigations along the Texas coast show that approximately 4000 metric tons of oil or less than 1 percent was deposited there. The rest of the oil, about 120,000 metric tons or 25 percent, sank to the bottom of the Gulf.
The oil had a drastic impact on the littoral crab and on the mollusk fauna of the beaches which were contaminated. The populations of crabs, e.g. the ghost crab Ocypode quadrata, were almost totally eliminated over a wide area. The crab populations on coral islands along the coast were also reduced to only a few percent of normal about nine months after the spill.
One study found that the most persistent issues were pollution of estuaries and coastal lagoons lining the bay, and especially the effects on breeding and growth of several food fish species.
Juan Antonio Dzul was a teenager when the Ixtoc 1 oil rig collapsed in June 1979 in the Gulf of Mexico, 70 miles (112.7 km) from the fishing town of Champotón where he grew up and still lives. The memory of the huge spill that followed is etched on his mind. "The oil covered the reefs and washed up on the shore. Fish died and the octopuses were buried under the oil that filled the gaps between the rocks where they live," he recalled in a phone interview. “Even today you can find stains on rocks a few centimetres deep, and if you stick something metal in them the smell of oil still escapes.”
The oil washed ashore, a foot deep in some places, as it was pushed north by prevailing winds and currents until it crossed the Texas border two months later and eventually coated almost 170 miles (273.6 km) of US beaches. The beach that caused most international concern in Mexico was Rancho Nuevo, a key nesting ground for critically endangered Kemp's Ridley sea turtles which had already lumbered up the sand in their hundreds to lay eggs. By the time the eggs hatched, the oil was lapping at the shore.
Fishing was banned or restricted by Mexican authorities in contaminated areas north and south of the well. Fish and octopus catches dropped by 50 to 70% from the 1978 levels. Some larger species with longer life spans took years to recover from the Ixtoc spill. It wasn't until the late-1980s that the population of Kemp's Ridley turtles, which lay a couple of hundred eggs a year, as opposed to the millions produced by shrimp, started recovering. The immediate losses from an oil spill continue to ricochet through larger species for generations.
There is much less information on the impact of the Ixtoc I spill on benthos (bottom dwellers). The best studies were on the Texas coast over 1000 km from the spill. Massive kills can occur when oil reaches the benthos in sufficient quantity. The only indication of a massive kill may be the remains of the dead organisms, but if they lack hard parts there will be little evidence.
A report prepared for the US Bureau of Land Management
concluded with respect to the spill's effect on US waters:
Semi-submersible
A semi-submersible is a specialised marine vessel with good stability and seakeeping characteristics. The semi-submersible vessel design is commonly used in a number of specific offshore roles such as for offshore drilling rigs, safety vessels, oil production platforms and heavy lift cranes.The...
drilling rig
Drilling rig
A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
Sedco 135-F in the Bay of Campeche
Bay of Campeche
The Bay of Campeche is the southern bight of the Gulf of Mexico. It is surrounded on three sides by the Mexican states of Campeche, Tabasco and Veracruz. It was named by Francisco Hernández de Córdoba and Antonio de Alaminos during their expedition in 1517...
of the Gulf of Mexico, about 100 km (62.1 mi) northwest of Ciudad del Carmen
Ciudad del Carmen
Ciudad del Carmen is a city in the southwest of the Mexican state of Campeche. Ciudad del Carmen is located at on the southwest of Carmen Island, which stands in the Laguna de Términos on the coast of the Gulf of Mexico. The 2005 census population was 154,197 people...
, Campeche
Campeche
Campeche is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. Located in Southeast Mexico, it is bordered by the states of Yucatán to the north east, Quintana Roo to the east, and Tabasco to the south west...
in waters 50 m (164 ft) deep. On 3 June 1979, the well suffered a blowout
Blowout (well drilling)
A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed....
resulting in one of largest oil spills in history.
Accident
Mexico's government-owned oil company PemexPemex
Petróleos Mexicanos or Pemex is a Mexican state-owned petroleum company. As of 2010, with a total asset worth of $415.75 billion, it is the second non-publicly listed largest company in the world by total market value, and Latin America's second largest enterprise by annual revenue as of 2009...
(Petróleos Mexicanos) was drilling a 3 km (1.9 mi) deep oil well
Oil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
when the drilling rig
Drilling rig
A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
Sedco 135F lost drilling mud circulation.
In modern rotary drilling, mud is circulated down the drill pipe
Drill pipe
Drill pipe, is hollow, thick-walled, steel piping that is used on drilling rigs to facilitate the drilling of a wellbore and comes in a variety of sizes, strengths, and weights but are typically 30 to 33 feet in length...
and back up the well bore 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 oil to fill the well column, blowing out the well. The oil caught fire, and Sedco 135F burned and collapsed into the sea.
At the time of the accident Sedco 135F was drilling at a depth of about 3600 metres (11,811 ft) below the seafloor. The day before Ixtoc suffered the blowout 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 on Sedco 135F, the drilling mud suddenly began to flow up towards the surface; by removing the drill-string the well was swabbed leading to a kick. Normally, this flow can be stopped by activating shear rams contained in the blowout preventer
Blowout preventer
A blowout preventer is a large, specialized valve used to seal, control and monitor oil and gas wells. Blowout preventers were developed to cope with extreme erratic pressures and uncontrolled flow emanating from a well reservoir during drilling. Kicks can lead to a potentially catastrophic...
(BOP). These rams are designed to sever and seal off the well on the ocean floor; however in this case the 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 blowout.
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 Sedco 135F 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 Gulf.
Volume and extent of spill
In the initial stages of the spill, an estimated 30000 barrels (4,769.6 m³) of oil per day were flowing from the well. In July 1979, the pumping of mud into the well reduced the flow to 20000 barrels (3,179.7 m³) per day, and early in August the pumping ofnearly 100,000 steel, iron, and lead balls into the well reduced the flow to 10000 barrels (1,589.9 m³) 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. Mexican authorities also drilled two relief wells into the main well to lower the pressure of the blowout, however the oil continued to flow for three months following the completion of the first relief well.
Pemex contracted Conair Aviation to spray the chemical dispersant Corexit
Corexit
Corexit is a product line of solvents primarily used as a dispersant for breaking up oil slicks. It is produced by Nalco Holding Company which is associated with BP and Exxon. Corexit was the most-used dispersant in the Deepwater Horizon oil spill in the Gulf of Mexico, with COREXIT 9527 having...
9527 on the oil. A total of 493 aerial missions were flown, treating 1100 square miles (2,849 km²) of oil slick. Dispersants were not used in the U.S. area of the spill because of the dispersant's inability to treat weathered oil. Eventually the on-scene coordinator
Federal On Scene Coordinator
The Federal On Scene Coordinator , is a designation in the United States for an individual that:*Is responsible for providing access to federal resources and technical assistance...
(OSC) requested that Mexico stop using dispersants north of 25°N.
In Texas, an emphasis was placed on coastal countermeasures protecting the bays and lagoons formed by the barrier islands. Impacts of oil to the barrier island beaches were ranked as second in importance to protecting inlets to the bays and lagoons. This was done with the placement of skimmers and booms. Efforts were concentrated on the Brazos-Santiago Pass, Port Mansfield Channel, Aransas Pass, and Cedar Bayou which during the course of the spill was sealed with sand. Economically and environmentally sensitive barrier island beaches were cleaned daily. Laborers used rakes and shovels to clean beaches rather than heavier equipment which removed too much sand. Ultimately, 71500 barrels (11,367.6 m³) of oil impacted 162 miles (260.7 km) of U.S. beaches, and over 10000 cubic yards (7,645.5 m³) of oiled material were removed.
Containment
In the next nine months, experts and divers including Red AdairRed Adair
Paul Neal "Red" Adair was an American oil well firefighter. He became world notable as an innovator in the highly specialized and extremely hazardous profession of extinguishing and capping blazing, erupting oil well blowouts, both land-based and offshore.-Life and career:Adair was born in...
were brought in to contain and cap the oil well. An average of approximately 10000 to 30000 bbl (1,589.9 to 4,769.6 m3) per day were discharged into the Gulf until it was finally capped on 23 March 1980, nearly 10 months later. In similarity to the Deepwater Horizon oil spill
Deepwater Horizon oil spill
The Deepwater Horizon oil spill is an oil spill in the Gulf of Mexico which flowed unabated for three months in 2010, and continues to leak fresh oil. It is the largest accidental marine oil spill in the history of the petroleum industry...
31 years later, the list of methods attempted to remediate the leak included lowering a cap over the well, plugging the leak with mud and "junk", use of huge quantities of dispersants, and spending months attempting to drill relief wells.
Aftermath
Prevailing currents carried the oil towards the Texas coastline. The US government had two months to prepare booms to protect major inlets. Pemex spent $100 million to clean up the spill and avoided most compensation claims by asserting sovereign immunitySovereign immunity
Sovereign immunity, or crown immunity, is a legal doctrine by which the sovereign or state cannot commit a legal wrong and is immune from civil suit or criminal prosecution....
as a state-run company.
The oil slick surrounded Rancho Nuevo, in the Mexican state of Tamaulipas
Tamaulipas
Tamaulipas officially Estado Libre y Soberano de Tamaulipas is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 43 municipalities and its capital city is Ciudad Victoria. The capital city was named after Guadalupe Victoria, the...
, which is one of the few nesting sites for Kemp's Ridley
Kemp's Ridley
Kemp's ridley sea turtle , or Atlantic ridley sea turtle is the rarest sea turtle and is critically endangered. It is one of two living species in the genus Lepidochelys Kemp's ridley sea turtle (Lepidochelys kempii), or Atlantic ridley sea turtle is the rarest sea turtle and is critically...
sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...
s. Thousands of baby sea turtles were airlifted to a clean portion of the Gulf of Mexico to help save the rare species.
Long-term effects
The oil that was lost during the blow-out polluted a considerable part of the offshore region in the Gulf of Mexico as well as much of the coastal zone, which consists primarily of sandy beaches and barrier islands often enclosing extensive shallow lagoonsThe oil on Mexican beaches that the authors observed in early September was calculated to be about 6000 metric tons. Based on reports from various groups and individuals, five times that figure is thought to represent a fair estimate of what had landed on Mexican beaches. Investigations along the Texas coast show that approximately 4000 metric tons of oil or less than 1 percent was deposited there. The rest of the oil, about 120,000 metric tons or 25 percent, sank to the bottom of the Gulf.
The oil had a drastic impact on the littoral crab and on the mollusk fauna of the beaches which were contaminated. The populations of crabs, e.g. the ghost crab Ocypode quadrata, were almost totally eliminated over a wide area. The crab populations on coral islands along the coast were also reduced to only a few percent of normal about nine months after the spill.
One study found that the most persistent issues were pollution of estuaries and coastal lagoons lining the bay, and especially the effects on breeding and growth of several food fish species.
Juan Antonio Dzul was a teenager when the Ixtoc 1 oil rig collapsed in June 1979 in the Gulf of Mexico, 70 miles (112.7 km) from the fishing town of Champotón where he grew up and still lives. The memory of the huge spill that followed is etched on his mind. "The oil covered the reefs and washed up on the shore. Fish died and the octopuses were buried under the oil that filled the gaps between the rocks where they live," he recalled in a phone interview. “Even today you can find stains on rocks a few centimetres deep, and if you stick something metal in them the smell of oil still escapes.”
The oil washed ashore, a foot deep in some places, as it was pushed north by prevailing winds and currents until it crossed the Texas border two months later and eventually coated almost 170 miles (273.6 km) of US beaches. The beach that caused most international concern in Mexico was Rancho Nuevo, a key nesting ground for critically endangered Kemp's Ridley sea turtles which had already lumbered up the sand in their hundreds to lay eggs. By the time the eggs hatched, the oil was lapping at the shore.
Fishing was banned or restricted by Mexican authorities in contaminated areas north and south of the well. Fish and octopus catches dropped by 50 to 70% from the 1978 levels. Some larger species with longer life spans took years to recover from the Ixtoc spill. It wasn't until the late-1980s that the population of Kemp's Ridley turtles, which lay a couple of hundred eggs a year, as opposed to the millions produced by shrimp, started recovering. The immediate losses from an oil spill continue to ricochet through larger species for generations.
There is much less information on the impact of the Ixtoc I spill on benthos (bottom dwellers). The best studies were on the Texas coast over 1000 km from the spill. Massive kills can occur when oil reaches the benthos in sufficient quantity. The only indication of a massive kill may be the remains of the dead organisms, but if they lack hard parts there will be little evidence.
A report prepared for the US Bureau of Land Management
Bureau of Land Management
The Bureau of Land Management is an agency within the United States Department of the Interior which administers America's public lands, totaling approximately , or one-eighth of the landmass of the country. The BLM also manages of subsurface mineral estate underlying federal, state and private...
concluded with respect to the spill's effect on US waters:
- "In spite of a massive intrusion of petroleum hydrocarbon pollutants from the Ixtoc I event into the study region of the South Texas Outer Continental Shelf during 1979-1980, no definitive damage can be associated with this or other known spillage events (e .g ., Burmah Agate ) on either the epibenthic commercial shrimp population (based on chemical evidence) or the benthic infaunal community . Such conclusions have no bearing on intertidal or littoral communities, which were not the subject of this study."
See also
- List of oil spills
- Notable offshore well blowouts
- Deepwater Horizon oil spillDeepwater Horizon oil spillThe Deepwater Horizon oil spill is an oil spill in the Gulf of Mexico which flowed unabated for three months in 2010, and continues to leak fresh oil. It is the largest accidental marine oil spill in the history of the petroleum industry...
- Ocean RangerOcean RangerOcean Ranger was a semi-submersible mobile offshore drilling unit that sank in Canadian waters on 15 February 1982. It was drilling an exploration well in the Grand Banks area, east of St. John's, Newfoundland, for Mobil Oil of Canada, Ltd. with 84 crew members on board when it sank...
- Piper AlphaPiper AlphaPiper Alpha was a North Sea oil production platform operated by Occidental Petroleum Ltd. The platform began production in 1976, first as an oil platform and then later converted to gas production. An explosion and resulting fire destroyed it on 6 July 1988, killing 167 men, with only 61...
- Thunder Horse PDQThunder Horse PDQThunder Horse PDQ is a BP plc and ExxonMobil joint venture semi-submersible oil platform on location over the Mississippi Canyon Thunder Horse oil field , in deepwater Gulf of Mexico, southeast of New Orleans, moored in waters of...
- Transocean John ShawTransocean John ShawTransocean John Shaw is a semi-submersible drilling rig designed by Friede & Goldman as a self-propelled modified & enhanced pacesetter, built and delivered in 1982 by Mitsui Engineering & Shipbuilding Ltd. in Japan....
External links
- Photo gallery by the US National Oceanic and Atmospheric AdministrationNational Oceanic and Atmospheric AdministrationThe National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
. - TV news reports from the 1970s regarding the Ixtoc spill and comparisons with the BP spill of 2010