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Unformatted text preview: e hydrocarbon zones at the production interval had failed and the casing had failed at the crossover joint. These failures would have resulted in hydrocarbon flow out of the well and up the riser. This scenario is depicted in Figure 7 below: “U‐tubing,” or reverse flow, occurs when fluids flow in the reverse direction and back up the inside of the casing. The “u‐tube effect” is the practice of putting a dense slugging pill (mud that is more dense than the mud in the drill pipe and the wellbore annulus) into the drill pipe in order to pull a dry string. The pill is pumped to the top of the drill string to push mud downward, out of the pipe, thus keeping the upper strands of the pipe empty. 158 64 Figure 7 – Flow Up the Annulus and Through Production Casing Crossover Joint After cementing the production casing, the Deepwater Horizon crew conducted a successful 2,500 psi positive casing test against the top wiper plug. 159 Although this pressure test (250 psi low/2,500 psi high) did not confirm aseal below the top wiper plug at the top of the float collar, it did provide evidence that the 9‐7/8 x 7 inc...
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