Abstract
April 20th was a calm sunny day in the Gulf of Mexico. The 126-strong crew of the Deepwater Horizon drilling rig was busy finishing work on the BP Macondo well at a remote location, as shown in Fig. 7.1, some 130 miles southeast of New Orleans and 420 miles east of Houston. Only a few routine operations were left to be completed before the rig would leave the site, with the Macondo well safely plugged with cement and waiting to be reopened at a later date. By March 8, the rig was already scheduled to be at a different location in the Gulf, so everybody was rushing about to mop up and stop the hemorrhage of money escaping from BP’s pocket at a rate of $1,000,000 per day.
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Notes
- 1.
Many of the industry-specific terms are explained in the Glossary at the end of this book.
- 2.
According to BP, the 6-5/8 inch pipe went down to 4,117 feet, 960 feet above the seafloor. The 6-5/8 inch pipe’s bottom end was then joined with a 5-1/2 inch pipe down to 7,567 feet, followed by a 3-1/2 inch pipe down to 8,367 feet, or 3,300 feet/1 kilometer into the wellbore. The reason for the three different pipe diameters was that the two larger diameter pipes would get stuck in the central production casing of the well. According to Halliburton, there was no 5-1/2 inch pipe and the 6-5/8 inch pipe went down to 7,545 feet.
- 3.
One barrel is 42 U.S. gallons or 159 liters.
- 4.
Displacing 16 pounds per gallon (ppg) mud with 8.6 ppg seawater.
- 5.
Displacing a 14 ppg mud with 8.6 ppg seawater. Because some of the riser was filled with a 16 ppg mud, the actual pressure decrease was even higher.
- 6.
Take an empty tall metal can. Press it down with your hands until it partially submerges in water. Then let it go. The can will jump up from the water. So could the production casing in BP’s well when pressure was decreased in the riser and both annular preventers were opened.
- 7.
The computerized sensors were registering the flow rate, but their readings were not interpreted correctly or fast enough to make a difference.
- 8.
Hearings focus on possible human factors in BP oil spill, by David S. Hilzenrath, Washington Post staff writer, Thursday, July 22, 2010.
- 9.
“I said: ‘What the hell do you mean you’ve lost the cofferdam? How did you lose it? Don’t give me that!’” Mr. Lynch, a BP vice president and a leader of the effort to kill the well, recalled. “This thing has taken off like a damn balloon. “The last thing you’d want is this thing filled with ice crushing the bottom of the vessel.” Clifford Krauss, Henry Fountain and John Broder, “Behind Scenes of Oil Spill Acrimony and Stress,” The New York Times, 8/27/2010.
- 10.
At one point, technicians said in interviews, a plumbing problem on one of the pump ships forced a delay in the operation. Then a screaming match over the radio between two senior engineers ended in one of them threatening to come over and throw the other overboard. Ibid., see Footnote 5, this chapter.
- 11.
Government officials insisted on reopening the well, but luckily the BP engineers prevailed.
- 12.
Because flow resistances are in series, the appropriate average is the length-weighted harmonic average of the hydraulic diameters of the annular space segments listed in the last column of Table 7.1. An argument advanced against this averaging relies on the choking effect of pipe collars and the narrowness of parts of the annular space. The pipe collars are very short and their choking effect would be small. They also would be eroded away by the reservoir fluid and sand. Thus, with time, the flow rate through the annular space would tend to increase.
- 13.
Initially a single-phase supercritical fluid that was neither oil nor gas flowed in the well. The narrowest annular space at the well bottom was exposed to this low-viscosity supercritical fluid that could easily flow through it.
- 14.
One-half of the total calculated flow rate of 37,000 barrels per day of oil and some gas liberated from the oil, gushing together from the blowout preventer. This calculation is tricky and highly uncertain, because if gas is given enough time to evolve into bubbles and then free gas, there will be not one, but 2.5–3 barrels of gas flowing out of the well for each barrel of oil.
- 15.
And 5–15 firehoses blowing gas, depending on how fast the gas was liberated.
- 16.
Their approach is called “Particle Image Velocimetry” or PIV. One of the coauthors, Dr. Paul Bommer of UT Austin, used a classical petroleum engineering approach to calculate the wellbore flow, and the Ros correlation to calculate the choking effect of the BOP. Significantly, for the unobstructed flow through the production casing, Dr. Bommer calculated the oil discharge to be 90,000–105,000 barrels per day.
- 17.
The completely unrestricted initial production rates of these wells can easily exceed 100,000–200,000 barrels of oil per day. This is why one needs to be careful when drilling any well in ultradeep water in the Gulf of Mexico.
Further Reading
Deepwater horizon accident investigation report, BP. www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/incident_response/STAGING/local_assets/down-loads_pdfs/Deepwater_Horizon_Accident_Investigation_Report.pdf. Accessed 8 Sept 2010
Deep water – the gulf oil disaster and the future of offshore drilling, report to the President, National Commission on the BP deepwater horizon oil spill and offshore drilling. www.oilspillcommission.gov/final-report. Accessed 11 Jan 2011
Feynman, Richard P.: Report of the Presidential Commission on the space shuttle challenger accident, appendix F – personal observations on the reliability of the shuttle. science.ksc.nasa.gov/shuttle/missions/51-l/docs/rogers-commission/Appendix-F.txt (1986). Accessed 15 March 2011
Gardner, Craig, National Commission on the BP deepwater horizon oil spill and offshore drilling – cement testing results, chevron energy technology company. motherjones.com/files/chevron_final_report.pdf. Accessed 26 Oct 2010
Patzek, T.W.: Energy and environment subcommittee of the energy and commerce committee, briefing. democrats.energycommerce.house.gov/documents/20100609/Patzek.Statement.06.09.2010.pdf. Accessed 06 Sept 2010
Ros, N.C.J.: An analysis of critical simultaneous gas/liquid flow through a restriction and its application to flowmetering. Appl. Sci. Rev. Sec. A. 9, 374–388 (1960)
Aliseda, A., et al.: Deepwater horizon release estimate of rate by PIV., www.doi.gov/deepwaterhorizon/loader.cfm?csModule=security/getfile&PageID=68011. Accessed 21 July 2010
Det Norske Veritas, final report for United States Department of the Interior Bureau of Ocean Energy Management, Regulation, and Enforcement Washington, DC 20240, Forensic Examination of Deepwater Horizon Blowout Preventer Contract Award No. M10PX0033, Volume I, final report, and Volume II, Appendices, Report No. EP030842. Accessed 20 March 2011
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Tainter, J.A., Patzek, T.W. (2012). What Happened at the Macondo Well. In: Drilling Down. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-7677-2_7
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