New mud supply process saves time and expense in riserless deepwater drilling

Described here are a methodology and process being employed to redefine interval limitations in deepwater operations. Discussions include limitation of conventional methods, types of riserless fluids used today, and details of a new process that supplies higher-density fluids by mixing concentrated mud onsite with seawater to avoid high-volume storage / supply limitations. Selected case histories illustrate applications in more efficiently running 20-in. casing to provide the base for more efficient final-string design. Deepwater drilling is taking place in certain offshore areas through young sedimentary sections often characterized by narrow margins between formation pore pressure and fracture pressure. As a result, drillers are challenged to prevent the upper-hole section from collapsing.1 The traditional approach of running an additional casing string may not be viable in deepwater wells due to engineering constraints or contingency cost.