On April 20, 2010, Deepwater Horizon, an oil drilling rig operated by private contractor Transocean, is set to begin drilling off the southern coast of Louisiana on behalf of BP. Chief Electronics Technician Michael "Mike" Williams and Offshore Installation Manager James "Mr. Jimmy" Harrell are surprised to learn that the workers assigned to test the integrity of recently completed cement work are being sent home early, without conducting a cement bond log (CBL), at the insistence of BP managers Donald Vidrine and Robert Kaluza. While Mike prepares the drilling team, including Caleb Holloway, Harrell meets with Vidrine and persuades him to conduct a test, which only serves to weaken the already poorly placed cement further. His patience thinning, and without waiting for Harrell to confirm the results, Vidrine orders the well to be flowed.