Sedco 135F – IXTOC I Blowout and Oil Spill

We learn from the past in order to prevent the bad incidents to be happened. This time we would like to discuss about Sedco 135F – IXTOC I Blowout and Oil Spill.  The Sedco 135F was perforating and drilling the IXTOC I well in 1979 for PEMEX, which is a petroleum company in Mexico owned by the state at the time when the well underwent an eruption. Through a drilling, the well had been dug up to 3.6 km with the 9-5/8″ casing set at 3.6 km. It has been vindicated by various studies that there was a failure in mud circulation (essentially mud is a massive and heavy weighted drilling fluid which is utilized as a lubricant for the drill bit, helps in cleaning the drilled rock from hole and present a column of hydrostatic pressure as a prevention from influxes), hence a consensus was reached that it is the best to pull the drill string & plug the well. The absence of mud column’s hydrostatic pressure triggered an unconstrained and liberal circulation of oil & gas to the surface, and this was what happened when the crew was working with drillstring’s lower part. The BOP was shut on the pipe however it was unable to chop the chunky drill collars, permitting oil and gas to come up to the surface where it burned and inflamed the Sedco 135F. The rig broke down and drowned on top of the wellhead space on the seabed, cluttering the seabed with debris like the rig’s derrick & 3000m of pipe.

Sedco-135F---IXTOC-I-Blowout-and-Oil-Spill-2

Sedco 135F – IXTOC I Blowout

At first the circulation in the well was 30,000 barrels/day (1 barrel = 42 US gallons = 159 liters) that later came down to approximately 10,000 bpd by trials to plug the well. Besides, couple of relief wells were dug and drilled to subdue some pressure and finally the well was killed 9 months later on March 23rd, 1980. The squirt and spill from the explosion caused extreme contamination (by June 12th, the oil slick measured around 180km by 80km), approximately 500 aerial missions were sent to spray dispersants on the water. The winds existing resulted in a lot of damage along the coastline of the country and Texas underwent the maximum damage out of all the states. The IXTOC I catastrophe was the most massive single spill, with a release of approximately 3.5 million barrels of oil.

Sedco 135F - IXTOC I Blowout and Oil Spill

Impacts of the spill

The explosion resulted in loss of oil which triggered pollution of a substantial area of the offshore place in the Gulf of Mexico and most of the coastal zone, that is, beaches & barrier islands wrapping around the shallow lagoons.

It was speculated that the oil on the beaches of Mexico in beginning of September was computed to approximately 6000 metric tons. As per the research and studies it was stated that, about 5 times that that figure is predicted to represent an approximate value. Further researches and studies by coastline of Texas vindicate that about 4000 metric tons of oil, that is almost 1 percent was precipitated. The remaining quantity of oil, that is approximately 120,000 metric tons or 25 percent, drowned into the Gulf.

The oil had a massive effect on the littoral crab & mollusk fauna of the contaminated beaches. It resulted in the extinction of various crab species in a vast location, for instance Ocypodequadrata (the ghost crab). Further, the populace of crabs on coral islands was also highly diminished.

The oil which was carried onto the shore at the depth of about a foot deep, like it was pushed north due to winds and currents till about 8 weeks later, it came across the border of Texas. Finally it covered about 170 miles (270 km) of American beaches. Globally, the most alarming issue was that of the Mexican beach -Rancho Nuevo, which was the prime shelter for the sea turtles of Kemp Ridley that had already slogged up the sand in massive numbers to lay eggs. When the eggs hatched, the beach was nearly sunk in oil.

 Ref: Wikipedia

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