During more than nine months, Ixtoc 1, an offshore oil well in the Gulf of Campeche, discharged about three million barrels of oil into the sea. Almost all of this oil ultimately was carried north in the western boundary current of the Gulf of Mexico.
On June 3, 1979, at approximately 3:30
When the well began to flow in spurts, the operator shut the annular preventer, which closed the annulus between the drill pipe and the casing. Gas and oil continued flowing through the drill collars, however, spilling oil on the derrick floor. At the same time, the annular preventer failed, and well pressure began to eject the drill collars from the well. The crew activated the shear rams to crush the casing and drill string, but the rams, designed to crush drill pipe, were unable to shear the much stronger drill collars. The well continued to flow and burn. After unsuccessfully attempting to cut the anchor lines so that the floating platform and rig could be towed away, the crew was driven away by heat and flames. Fifteen hours later, the drilling rig collapsed and fell into the water. The remainder of the drilling unit was towed from the site on June 4, 1979, and scuttled on July 12 in 1,800 fathoms of water more than two hundred miles offshore; the unit disappeared in ten minutes without visible signs of pollution.
The well discharged gas and oil about twelve meters above the ocean floor through the apparently undamaged BOP stack; this was seen through remote-control videotape cameras. At first, PEMEX estimated the flow to be about 30,000 barrels per day. Later appraisals put the initial flow at between 5,000 and 10,000 barrels per day. Calculations based on inexact measurements of the oil slick floating on the surface yielded estimates of between 20,000 and 30,000 barrels per day. PEMEX also estimated that 7,500 barrels per day were being recovered by collector equipment and that 2,500 barrels per day were dispersed in the Gulf of Mexico. Perhaps as much as a third of the discharged oil burned and evaporated.
Escaping oil and gas quickly rose in the seawater. Churning and heating emulsified the oil and evaporated or burned the more volatile, toxic fractions. The resultant oil slick was a viscous emulsion of 70 percent water and 30 percent heavy oil referred to as mousse. Analysis of the mousse indicated that approximately 30 percent of the oil from the well burned. In addition to the slick, which was between one and three millimeters thick, the upper few meters of the water contained a cloudy suspension of very small emulsion particles.
PEMEX contracted with the Red Adair Company to bring the well under control. Their first attempt was to close the valves on the BOP, which required removing wreckage around the well head and repairing the BOP stack. This work began on June 3; on June 24, the flow was stopped for about one hour. After one hour of pumping cement into the well, however, the well again broke through the wellhead below the control valves and resumed its uncontrolled blowing. The well was reignited to dispose of as much oil and gas as possible.
Steel balls, lead balls, and gelatin were pumped down the well in repeated attempts to check or stop the flow. After the injection of nearly 100,000 balls, the flow reportedly decreased from 20,000 to 10,000 barrels per day during the week of August 6. The reduction was temporary, however, and the balls were expelled from the well. A later injection of 108,000 balls reportedly reduced the flow to a “sputter” of 10,000 barrels per day on October 12. This process continued and appeared successful in holding the flow to about 10,000 barrels per day.
In addition, an inverted 300-ton steel cone called a sombrero was built to fit over the blowout preventers on the ocean floor. It was hoped that the device would catch the escaping oil and gas and feed it to a collecting system. On September 24, the sombrero, having been found defective, was returned to the manufacturer for modification and repair. On October 15, PEMEX announced that the sombrero was collecting between 80 and 85 percent of the intermittent spill. In late November, however, the sombrero was capturing only 6,000 of the 10,000 barrels per day flowing from Ixtoc 1. According to PEMEX, half of the escaping 4,000 barrels burned and the rest was skimmed or chemically dispersed. On December 24, PEMEX reported that the sombrero had been damaged by heavy weather and abandoned. Jerome Milgram,
At least four different organizations using different equipment attempted to skim emulsion from the slick at or near the well site. Norwegian pollution abatement specialists from Statoil, the Norwegian national petroleum company, brought containment and pickup devices thought capable of gathering more than 30,000 barrels of oil per day. Although the operation was abandoned after having been judged ineffective, Statoil claimed to have recovered as much as 8,760 barrels of crude oil in one twenty-four-hour period. Oil Mop, Incorporated, attempted to gather the oil by towing continuously circulating loops of oleophilic rope through the slick. The ropes were pulled through a roller on a barge to squeeze out the oil and then returned to the slick. These machines reportedly recovered about 50,000 barrels of mousse during one month’s operation. Shell Oil offered the use of an experimental sock skimmer that was thought capable of picking up 150 barrels of mousse per hour. The device was technically deficient, however, and was removed from the scene within the first month of operation. At least three skimmers from the Southern California Petroleum Contingency Organization came onto the site on July 9. In addition to skimming, chemical dispersants were applied close to the site and in areas where the slick appeared to threaten coastlines.
The Ixtoc 1 oil well had discharged about three million gallons of oil off the Mexican coast by the time the accident was contained in March, 1980.
A relief well, Ixtoc 1A, began drilling on June 10 to tap the reservoir at or near the bottom of Ixtoc 1. A second relief well, Ixtoc 1B, began shortly thereafter. These wells, drilled with advice from Red Adair, ultimately injected drilling mud, water, and cement into the reservoir rock and the base of the well, which cut off the flow. The first well, Ixtoc 1B, penetrated the producing zone in early December, and shortly after that, it was observed that seawater was mixed with the blowout oil. By December 24, water, jell, and brine pumped into the blowout through the wellhead and the Ixtoc 1B well had cut the flow to 1,200 barrels per day. In mid-January, Red Adair reported that Ixtoc 1A was slowly and cautiously being directed to intersect the base of the Ixtoc 1 casing, so that the well could finally be controlled. By February 11, Ixtoc 1A had pumped seawater, hydrochloric acid, and mud directly into the well, and Ixtoc 1B had pumped nearly 4.5 million barrels of fluid into the reservoir. After a delay caused by weather, the flow from Ixtoc 1 ended. The well was finally plugged with three cement plugs at 11:00
PEMEX estimated that about three million barrels of oil were spilled by Ixtoc 1. Although small amounts were collected from the surface, more than half of the unburned oil drifted away on the surface and within the upper layers of the sea. Almost all of this oil ultimately was carried north in the western boundary current of the Gulf of Mexico. Hardly any oil reached the shore east or south of the well.
Approximately 4,000 tons of oil from Ixtoc 1 washed ashore in Texas, more than 600 miles from the blowout, between mid-August and early September, 1979. Beaches from the Mexican border to Aransas County were fouled. Most of the beached oil, however, was removed on September 13, 1979, by tropical storm Henri. Exposed beaches of fine-grained sand were left with only light tar. Beaches of mixed sand and shell fragments remained significantly oiled, mostly by sediment-laden tar balls. Large tar mats, containing 8 percent oil, 15 percent water, and 77 percent sediment, remained underwater at the toe of the beach in several localities after the storm. These mats contained approximately 180 tons of oil, less than 5 percent of the total quantity originally beached. Less than 0.8 percent of the approximately 476,000 tons of oil released by Ixtoc 1 into the Gulf of Mexico washed ashore in Texas and less than 0.04 percent remained as tar mats after the storm. Although Ixtoc 1 continued to flow until March, 1980, negligible additional oil washed ashore. Tar balls that remained on the beach during the summer of 1980 could not be distinguished from chronic accumulations.
In late August, PEMEX reported that oil slicks were nearing the Tampico shoreline, but the company claimed they were able to disperse them chemically and that no beaches on the Mexican coast were stained by the blowout. American observers, however, reported that there was oil on those beaches and that it was gone after Henri passed through.
September 8-9, Congress held hearings on the spill. Great economic losses had been reported as a result of major reductions in tourist traffic, recreational and commercial fishing, and the leasing of winter residences. The U.S. Coast Guard and SEDCO detailed how they managed the spill. Concern about the pollution of marine habitats was later diminished by a Texas study in mid-November that found Texas shrimp uncontaminated.
By September 24, a $155 million class-action suit had been filed against SEDCO, Permargo, and PEMEX on behalf of as many as one hundred fishermen. Later, taxing agencies in Hidalgo and Cameron counties and several Padre Island property owners filed two $100 million suits. On October 18, the state of Texas filed suit for $10 million in damages against SEDCO and Permargo, and on the same day the U.S. government filed for $6 million against SEDCO for cleanup costs in addition to substantial damages. In September, SEDCO requested clearance from all blame or limitation of liability to $300,000. In early October, José López Portillo announced that Mexico would not pay damages because the U.S. government refused to pay damages for saltwater incursion from the Colorado River.
PEMEX spent approximately $131.6 million to control the well and contain the spill. Dispersants were sprayed on the oil and booms placed across gaps in the barrier beaches north of Tampico in an attempt to protect the Mexican beaches and lagoons. A substantial amount of oil did reach shore, however, where it was cleaned. Ocean currents moved the remainder northward. The U.S. Coast Guard, in anticipation of the late summer arrival of the slick on U.S. coasts, installed many booms in estuaries and beach gaps between Brownsville and Aransas Pass. These were reasonably effective but did not totally prevent incursion of oil, especially oil suspended in water.
The environmental consequences of the spill were significant but not catastrophic. Laboratory studies found Ixtoc 1 oil to have low toxicity. Some eggs, larvae, and immature animals were affected, but the effects on local animals such as shorebirds were minimal. Intertidal beach faunas seemed somewhat reduced, but only two species experienced major declines. The impact on marsh vegetation, marine turtles, and mammals was likewise minor. The evaluation was hampered to some extent by the difficulty of distinguishing between the effects of the spilled oil and those of natural causes and normal population variation.
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American Petroleum Institute. 1981 Oil Spill Conference (Prevention, Behavior, Control, Cleanup). American Petroleum Institute Publication No. 4334. Washington, D.C.: Author, 1981. Describes the U.S. National Strike Force organization and action in response to the Ixtoc 1 blowout, as well as the plans to assess the damage from the Ixtoc and future spills. Also evaluates dispersant application and describes the physical and biological impact and persistence of Ixtoc oil on the Texas coast. Technical, but with readable summaries and introductory material. -
Atwood, Donald K., ed. Proceedings of a Symposium on Preliminary Results from the September 1979 Researcher/Pierce Ixtoc-1 Cruise. Boulder, Colo.: National Oceanographic and Atmospheric Administration, 1980. Presents the results of investigations of the chemical oceanography of the Ixtoc 1 spill and compares it with other major spills. Includes a comprehensive description of the spill and its spread. Fairly technical. -
Hooper, Craig H., ed. The Ixtoc 1 Oil Spill: The Federal Scientific Response. Boulder, Colo.: NOAA Hazardous Materials Response Project, U.S. Department of Commerce, 1981. Summarizes the work of about two hundred scientists forecasting oil movement in the Gulf of Mexico, advising on beach processes, evaluating danger to organisms, and determining changes in oil composition and toxicity of the oil during its time at sea. Comprehensive nontechnical summary, followed by technical articles. -
“Ixtoc Blowout Capped as Ten-Month Struggle Finally Succeeds.” In International Petroleum Encyclopedia 1980, edited by John C. McCaslin. Tulsa: Pennwell, 1980. Summarizes events from the initial blowout to the capping of the well. Nontechnical and with instructive diagrams. -
U.S. Congress. Committee on Merchant Marine and Fisheries. The Impact of the Mexican Oil Well Ixtoc 1 and the Resultant Oil Pollution on Texas and the Gulf of Mexico. 96th Congress, 1st session, 1980. Senate Report 96-19. Transcribed testimony and written commentary on all aspects of the Ixtoc 1 blowout and its effects. Includes statements by Texas congressmen, senators, state legislators, and mayors; SEDCO; politicians; business people; environmentalists; and scientists. Unedited and unorganized.
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