and OIM in the command organization. Crew members stood watches in a prescribed rotation, and crews were regularly cycled on and off the rig to support continuous operations.

The Deepwater Horizon worked on the Macondo well under the command of Transocean even during drilling operations, as contracted by BP. BP’s on-site direction was provided by two well site leaders. Four others from BP (a well site trainee and three subsea engineers) were also aboard. In addition, BP separately contracted for services aboard the Deepwater Horizon from contractors, including Halliburton (cementing), Sperry Sun (well data logging), M-I SWACO (mud material and engineering), Schlumberger (well and cement logging services), Weatherford (provider of casing accessories), and Tidewater (owner–operator of the offshore supply vessel Damon B. Bankston) (Transocean 2011a, 17). Further information is given in Chapter 5.

Six large diesel generators powered the rig’s integrated electric plant. Propulsion and dynamic positioning were produced by steerable thruster pods. Generated electrical power was also consumed by hotel loads, drilling equipment loads, and damage control equipment including pumps for firefighting and dewatering. A backup diesel generator, smaller than any of the six main units, provided emergency power for lighting and restarting the main engines in the event of a loss of main power. Propulsion power plays a vital role in maintaining the rig’s position, since wind and currents constantly work to move the rig away from the wellhead, risking separation of the riser from the wellhead. Thus, the rig’s design and maintenance with regard to sustaining reliable propulsion power play important roles in drilling operations safety, as well as in traditional marine navigation safety.

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FIGURE 4-1 Basic dimensions of the Deepwater Horizon rig while drilling. Source: Chief Counsel 2011, p. 26.



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