Rigzone has received information from a reliable source concerning what really happened on the Deepwater Horizon. The following is a technical look at the to-do list and what likely caused the blowout. We encourage the Rigzone readership to respond with their own technical conclusions to this article.
The Deepwater Horizon on April 20th had finished running and cementing a 9-5/ 8" x 7-3/8" tapered production liner to 18,303'. The cement job had also been completed. So what work remained to be done and what went wrong?
The 9 7/8" liner (not the tapered production liner) was set at 17,168'. Everything below the 16" casing shoe at 11,585' was a liner. But, rather than walk up the hole one casing string at a time, click here to see the the well design schematic for exact casing string sizes and depths. Note that the casing sizes and depths and the mud weight shown on our schematic are actual and not hypothetical. So with the production liner set, cemented and tested at 18,303 what else had to be done before BP could release the rig? The P&A program might have called for an EZSV packer in the 11 7/8 inch which would have been tested top and bottom, (positively and negatively) prior to setting the final cement plug(s) and displacing the mud in the riser with sea water. So from completion of the cement job the to do list at a minimum would have included the following steps:
- Pull out of hole and lay down liner hanger running tools.
- Rig up wire line and run 11 7/8 EZSV packer to above production liner top.
- Pick up RTTS tool w/bypass and trip in hole to set at 8500.
- Negative test with sea water to 8000 feet. Monitor test for one hour.
- Reverse out sea water with 14 lb mud.
- Pull out of hole.
- Trip in hole open ended to 8000 feet.
- Displace well bore and riser with sea water.
- Set required cement plug(s).
- Pull out of hole laying down pipe.
- Pull BOP Stack.
- Install dust cover and move rig.
The blow out occurred 20 hours after cementing the tapered production liner and the work described above could not have been done in 20 hours. What you can do in 20 hours is pull out the hole, lay down liner hanger running tools, run back in with drill pipe open ended and displace well bore and riser with sea water. Your comments are welcome and if they come in anonymously that confidentiality will be respected.