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Unformatted text preview: gth, 68 drill bit size, anticipated hydrocarbon flow, and hydrocarbon type. BP originally designed the Macondo well to include seven casing strings to reach the target well depth. However, based on the actual conditions encountered during drilling, BP used nine casing strings to reach total depth. Conditions encountered during drilling can drive changes in casing programs. For example, circulation loss events occurred in the open‐hole section of the Macondo well. Lost circulation is the loss of drilling fluids (such as drilling mud and spacer) into the formation. This loss of drilling fluid is observed during the circulation of drilling fluids. When less fluid is returned up the well annulus than was pumped into the well through the drill string, this means a loss of drilling fluid – lost returns – has occurred. These lost returns were a factor in BP’s decision to limit the well total depth to 18,360 feet (short of the 20,200 feet originally planned) and also led BP to revise the well’s casing design program to account for mud weight and fracture gradient drilling margin issues. Specifically, BP modified its casing program several times because of: (1) a well control event in March 2010 that resulted in the drill pipe becoming stuck; (2) changes in pore pressure estimates; and (3) well ballooning. 69 After BP revised its casing program, it submitted a revised Application for Permit to Drill to MMS for approval. 70 Burst pressure is the theoretical internal pre...
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This note was uploaded on 01/18/2014 for the course BEPP 305 taught by Professor Nini during the Fall '11 term at UPenn.

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