Summary

Halliburton confirmed support of investigation of the disaster of Deepwater Horizon rig in the Gulf of Mexico. Halliburton performed several services and had 4 employees on the rig. All were evacuated by the U.S. Coast Guard. Halliburton had completed the cementation of the final production string 20 hours prior to the accident. Tests to demonstrate the integrity of the casing were completed. At the time of the accident, placement of the final cement casing plug had not occurred. 

Analysis

The above is from a Rigzone Newsletter of April 30. The Halliburton report suggests casing failure. In deep water operations, the composition of the cement is carefully designed to set timely taking into consideration the high pressure/high temperature environment that would obtain in a well of that depth (about 18,000 feet). Once the job is complete, certain tests are made to insure that the job was a success. A key test is a check of the floating equipment. Long strings of casing are normally "floated" in, i.e. the string is equipped with both a float shoe and a float collar so that drilling fluid cannot enter the bottom of the string. The reason for this is to reduce the weight of the hook load which places a compressive burden on the derrick. The accident occurred 20 hours after the cementing. Depending on the design of the job, oil well cements are expected to set in 18-24 hours. The final cement plug would have been set by running a string of drill pipe into the well "open ended", i.e. nothing would have been attached to the bottom joint of drill pipe. It is at this point that no further information has been released. If the final plug had been set, the remaining completion fluid would have remained in the casing. Then a cast iron bridge plug would have been set several feet blow the casing head flange. At that point the well would have been abandoned. The subsea blowout preventer stack would have been disconnected and the final operation would have been to pull the riser with the subsea stack attached to the bottom of it. This did not happen. For reasons not yet revealed and possibly not  determined, a flow of natural gas and crude oil arrived at the surface and exploded. The force of the explosion must have damaged the ballast control equipment which led to the sinking of the rig. Until more information is made public, no conclusions can be drawn. The cause of the accident remains speculative.

Analyses are solely the work of the authors and have not been edited or endorsed by GLG.