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Abstract

The Well IXTOC No. 1 was located 94 km Northwest of Ciudad del Carmen, Campeche in the Gulf of Mexico. The drilling objective was to determine the existence of hydrocarbons in carbonate rocks of the paleocene, cretaceous and jurassic formations; the drilling operation was initiated on December 1st, 1978. On June the 3rd at 2:45 - hrs., the Well started to flow out of control. This was the beginning of the IXTOC No. 1 blowout which lasted nine months and twenty-two days.

The purpose of this paper is to describe in a summarized form, the well control activities, including: the operations to reduce the flow of the well, the drilling of the directional control wells Ixtoc 1-A and Ixtoc 1-B, the installations used to assist in the operation and the pumping of fluids from the directional Wells to pumping of fluids from the directional Wells to achieve the dynamic control on the Ixtoc No. 1 Well, that brought about the final plug operation.

Background

The IXTOC No. 1 Well was drilled with a semisubmersible platform "Sedco 135", hired by Pemex. The water depth was 50.5 m and the space between rotary table and the ocean floor was 83.7 m.

Figure 1 illustrates the cemented casing and the geological section drilled. During drilling with a 152.4 mm (6") bit, at a total depth of 3627 m, there was a total lost circulation in fractured and porous carbonate rocks and an attempt was made at re-establishing circulation by lowering muy density from 1.14 g/cc to 1.12 g/cc adding fibrous and granular bridging materials up to 15 kg/m3 without success. After six hours had elapsed with no flow, it was decided to trip out the drilling string to eliminate the bit and the drill collars and trip back in to bottom with open ended drill pipe and try to shut off the loss circulation zone by placing a combination of cement and diesel oil plugs.

On June 2nd, at 22:00 hrs., the pull out operation started and at 2:45 hrs. June 3rd, the Well began to blow out. This took place having the top portion of the 120.65 mm (4 3/4") drill collars supported on the rotary table with the slips, the safety collar installed, and the last three joints of the pipe which had just been backed off suspended from the elevator. Gas and oil began to flow and spray under pressure from the well, forming a dense curtain which prevented the drilling crew from continuing the prevented the drilling crew from continuing the job, and the order was given to abandon the platform. platform. When lowering the first lifeboat, the derrick of the rig caught fire and it is believed that 10 to 15 minutes elapsed from the moment flow was detected until fire commenced. Fortunately, the 70 workers on the platform were evacuated and there were no casualties.

The rig, the stand pipe and part of the drilling equipment collapsed over the blow-out preventors tilting them by 10 degrees to 12 degrees in the 78 degrees South-west direction. Later, the platform was withdrawn from the location and upon platform was withdrawn from the location and upon examination it was realized that it would no longer be useful. Therefore, it was intentionally sunk in the open sea. Pemex hired the services of world known specialists to assist in the control operations.

Skin divers and television cameras were used in order to verify that the blow-out preventors could still be used to control the Well. Therefore, the necessary lines were connected to hydraulically operate them as well as a 79.375 mm (3 1/8") hose thru which kill fluids were to be pumped. On June 24th, before starting fluid pumped. On June 24th, before starting fluid injection, the Well was only flowing thru the blowout preventors and there was no evidence of flow outside them. Figure 2 shows the submarine stack of the well with the special hose for the injection of fluids and bridging materials.

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