Surface BOP,Slim Riser,or Conventiona! 21-in.Riser-Which Is Best To Use?

摘要

One of the major cost components of ultradeepwater wells is the cost to build and operate the new fifth-generation mobile offshore drilling units (MODUs) required to drill in these water depths.Until recently,the only option for operators and contract drillers was to use a conventional 21-in.riser with an 18(3/4)-in.subsea-blowout-preventer (BOP) system.In the early 2000s,a new,somewhat radical concept of placing a surface-BOP stack (SBOP) directly under the rotary and running a high-pressure-casing riser below the SBOP to the seafloor was used.The full-length paper discusses a recent modification to the SBOP concept and a third proposed concept as alternatives to the 21-in.riser.