∼∼≈∼∼≈∼∼ Deepwater 1 Horizon ≈≈∼≈≈∼≈≈ ∼∼≈∼∼≈∼∼≈≈∼≈≈∼≈≈

Deepwater Horizon was the name of the exploration rig owned by . The rig was operating at the Macondo well, which was licensed to BP for drilling and production. Transocean’s rig and crew were drilling BP’s Macondo well with some oversight from BP personnel.

Geography and Geology

Figure 1 shows Macondo well location in Block 252 of Mississippi Canyon. This location is 48 miles from the nearest land, 114 miles from Port Fourchon that services and supplies oil rigs and 154 miles from Houma helicopter base used for transporting oil & gas personnel to the rigs in .

Figure 1: Macondo well location. Source: : Accident Investigation Report (2010).

Figure 2 shows the formations, casings and pressure levels at Macondo well. Formations are primarily of two kinds: mudstone (shale) and siltstone (clastic rock including clay) mixed with mudstone and sand- stone. Casings get narrower deeper in the well and house the production string. The production string goes down to 18,349 feet from the rig floor. 13,282 feet of this is wellbore and is drilled starting from the sea floor. The remaining 5,067 feet is the depth of the water at Macondo well. Figure 2 also has the pressure levels in the wellbore as a function of the depth. The pressure always increases with depth so all the graphs are going down and to the right. Pore pressure is the pressure of the liquids in theDo formations whereas NOT the fracture pressure Post is the pressure that or the formation can Copy stand before 1 Keywords: Risk involved in complex exploration & production projects. This case is prepared for class discussion by Metin C¸akanyıldırım. If you want to use this case, please get written permission from Metin C¸akanyıldırım by sending an email to [email protected]. Compiled at 21:00 on Thursday 7th February, 2019. Deepwater Horizon by Metin C¸akanyıldırım

Figure 2: Macondo well. A: formations, B: casings and possible flow of gas, C: pore pressure vs. fracture pressure; all in terms of the TVD (total vertical depth) in feet from the rig floor. Source: Hickman et al. (2010). cracking. The mud in the wellbore is used to counter these pressures. If the mud pressure is less than the pore pressure, the liquids flow into the wellbore. If the mud pressure is more than the fracture pressure, the mud cracks wellbore formations (unintentional fracking). At any given depth, the mud pressure must always be more than pore pressure and less than fracture pressure. That is, the mud pressure graph must lie between black and red curves in panel C of Figure 2. Unfortunately, the gap between these curves is narrow in deepwater drilling wells of Gulf of Mexico. This makes the adjustment of mud weight challenging in the drilling projects of the gulf.

Events Before and After Deepwater Horizon Disaster

As a background material, Ingersoll et al. (2012) lays out the events before and after the BP at the Macondo well on April 20, 2010. After the spill, the US House of Representatives started an investigation led by congressman Henry Waxman, chairman of the Committee on energy and Commerce, and congressman Bart Stupak, chairman of Subcommittee on Oversight and Investigation. The committee invited BP CEO for his testimony to the US Congress on June 17, 2010 and sent a letter (Waxman and Stupak 2010) to him on June 14 to hint at some questionable decisions made and actions taken during the drilling and completion of Macondo well;Do see Figure 3. The NOT letter lists crucial BP Post decisions: or Copy (1) the decision to use a well design with few barriers to [uncontrolled] gas flow [from the reservoir to the drilling rig]; (2) the failure to use a sufficient number of ”centralizers” [that keep the casing/pipes stable,

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perpendicular to the seabed and at the center of the wellbore] to prevent channeling [air/gas pathway from reservoir to annulus and possibly all the way to the surface] during the cement process; (3) the failure to run a cement bond log to evaluate the effectiveness of the cement job; (4) the failure to circulate potentially gas-bearing drilling muds [sufficiently] out of the well; (5) the failure to secure the wellhead with a lockdown sleeve before allowing pressure on the seal from below.

BP conducted its own investigation and released a report to provide its own account of events, actions and decisions (Deepwater Horizon: Accident Investigation Report 2010). This investigation report has a chronology of events that led to the spill; see Section 3. These events are chronologically listed and explained in Events sheet of the spreadsheet deepwaterHorizonEventsData.xlsx available from MERIT website. Negative-pressure test was one of the critical events that took place on April 20. It started about 3 pm and consisted of three different set ups to read wellbore pressure. A negative pressure test involves emptying out the mud and liquids (water, spacer) in a certain sealed portion of the wellbore to see that the pressure in that portion can remain at zero for 10-20 minutes. If the pressure does not reach to zero or does not remain at zero, one should suspect from an underbalance: movement of hydrocarbons into the wellbore from the surrounding formations as a result of compromised well integrity. The pressure can be read from the production line or from the kill line. These lines can be thought as two parallel pipes connected to the blowout preventer (BOP) at the sea floor and to the drilling rig above the sea. The production line carries hydrocarbons during production and the kill line is narrower than the production line and is used for pumping in/out mud or other liquids directly to the BOP. In a successful negative pressure test, both lines connected to the same portion of the wellbore must show the same pressure. In the case of Deepwater Horizon, the crew had to work hard to get a reading of zero psi (pounds per square inch) on the production line. They had to bleed off too much liquid out of the wellbore thinking that this would help reducing the pressure. This decreased the liquid level at the surface and the crew looked down the production line on the rotary table of the platform to see how deep the liquid went down. Then they added spacer (liquid barrier between mud and seawater) and pumped seawater with an attempt to replace the mud with the seawater only above the BOP. This spacer is not commonly used in the industry. Its density is far higher than that of the water. When mixed with seawater, it can possibly fall below the seawater over enough time. The spacer was laid between the mud and seawater, these three had to be piled up on top of each other in the order of the mud, spacer, seawater as the depth increased. The spacer, failing to separate the mud and seawater, probably unintentionally went below the seawater even below the BOP. This made it harder to compute the amount of mud or seawater to pump out/in and to interpret the results of pressure tests. When another negative pressure test was attempted by reading the pressure on the kill line, its pressure reading turned out to be less than that of the production line. For a while, the production line showed significant positiveDo pressure NOT while the kill line showed Post no pressure. The or crew was confused Copy with this inconsistent reading. It is impossible to exactly know what might have caused this inconsistency. However, a credible theory suggests that the narrow kill line was temporarily clogged by the non-traditional spacer. Later the crew decided to open the kill line and to see if any mud came to the surface, which did not initially. Consequently, the crew (or some of them) inclined to interpret the absence of the mud on the rig

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Sea level 0 metres

Wide Narrow production kill line line

Sea floor −1, 525 metres BOP

Ruptured outer casing

Production casing Outer casing Cement

Resevoir Do NOTHydrocarbons Post or Copy −5, 500 metres

Figure 3: Deepwater horizon rig and Macondo well.

4 Deepwater Horizon by Metin C¸akanyıldırım as a sign of a successful negative pressure test. The movie Deepwater Horizon (2016) showcases the tense disagreement among the crew members as to how to interpret the negative pressure test results. It is hard to understand the steps of the negative pressure test from the movie, Chapter 4.6: Negative Pressure Test in the report titled Deep Water: The Gulf Oil Disaster and the Future of Offshore Drilling (2011) is far more instructive. After the incident, through liquid flow modelling, it is determined that hydrocarbons broke into the wellbore at 20:52. In about 40 minutes, they passed into the riser (above the seabed). At 21:42, the mud under the pressure of the gas overflowed onto the rig floor. In 7 minutes, rig lost the power and two successive explosions happened. By 23:22, coast guard helicopters arrived and survivors were taken to the close-by mud ship Damon Bankston. Deepwater Horizon sank at 10:22 in the morning of April 22.

Questions to Consider for the Case Discussion

A list of questions is provided below. A case report does not need to address all of these questions but should instead focus on some of these. The report can also identify other issues and provide a discussion of those issues.

1. List the key companies that played a role in drilling and completion. For example, Sperry Drilling was collecting data from drilling sensors and interpreting them and Weatherford was the manufac- turer of drillstring centralizers. Neither of these companies played a key role. You should focus on other companies.

2. List the key technical and managerial issues that led to the oil spill. Associate each technical issue with one or some of the companies which were responsible for the issue.

3. Put yourself into the shoes of three companies responsible for key technical issues and use your empathy to explain why they did what they did.

4. Before the disaster, there were some conflicts among the companies and the people. Some people are more risk averse than others. Some companies have risk management groups whose responsibility is to monitor and control the risk. The steps and precautions used in risk control can slow down the progress of a project. Put these general remarks into the context of Deepwater Horizon and give examples of who wanted to progress fast and who wanted to be more cautious.

5. Can you make suggestions as to how disasters like Macondo oil spill can be avoided? Note that BP had a refinery fire a few years before the oil spill, it investigated the fire and made suggestions. Apparently those suggestions did not work. Why will your suggestions work?

• A common suggestion after an accident is to tighten the safety regulations. Tightening of regula- tions requires first understanding the processes (e.g., drilling completion) and equipment (type and number of drillstring centralizers) & material (e.g., type of cement) used, then standardiz- ingDo them with rules. NOT Afterwards, companies Post and employees are monitored or and checkedCopy to see if they abide by the rules specified in the regulations. This methodology is used in other industries such as manufacturing or healthcare. In the context of deepwater offshore drilling, what might be some challenges associated with using the methodology?

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6. Ethics is doing what is right when you have a legal right not to do it. From an ethical standpoint, which company or who is right or wrong in the retrospect? If you can identify some unethical behav- ior, what would be a way to correct such behavior? What, if any, role can (university) education play in instilling strong ethical values to the members of our society?

This case focuses on what led to the accident and immediate aftermath. Intentionally, the focus on oil spill, cleaning efforts, environmental, societal issues and fines is limited. Depending on the background or interests of its author, a case report can address issues surrounding the oil spill. In that case, the report should address fewer of the questions listed above.

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References Deepwater Horizon. 2016. Movie produced by Summit Entertainment, Lionsgate Company. http://www.deepwaterhorizon.movie Deepwater Horizon: Accident Investigation Report. 2010. Prepared by BP, Sep 8. http://www.bp.com/content/dam/bp/pdf/sustainability/issue-reports/Deepwater Horizon Accident Investigation Report. pdf. Deep Water: The Gulf Oil Disaster and the Future of Offshore Drilling. 2011. Report prepared by a US Presidential Committee co-chaired by Senator Bob Graham and William K. Reilly. https://www.gpo.gov/fdsys/pkg/GPO-OILCOMMISSION/pdf/GPO-OILCOMMISSION.pdf Hickman, S.H., P.A. Hsieh, W.D. Mooney, C.B. Enomoto, P.H. Nelson, L.A. Mayer, T.C. Weber, K. Moran, P.B. Flemings and M.K. McNutt. 2012. Scientific basis for safely shutting in the Macondo Well after the April 20, 2010 Deepwater Horizon blowout. Proceedings of the National Academy of Sciences of the USA, Vol.109, No.50: 20268-20273. http://www.pnas.org/content/109/50/20268.full.pdf Ingersoll, C., R.M. Locke, C. Reavis. 2012. BP and the Deepwater Horizon Disaster of 2010. Revised on Apr 3. https://mitsloan.mit.edu/LearningEdge/CaseDocs/10%20110%20BP%20Deepwater%20Horizon%20Locke.Review.pdf. https://www.goodreads.com/work/quotes/27417251-supreme-justice-reeder-and-rogers-1 Waxman, H., B. Stupak. 2010. June 14 letter from the US Congressional Committee on Energy and Com- merce https://energycommerce.house.gov to British Petroleum http://www.bp.com.

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