Importance

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Abstract

A well system, and a method for installing the well system, for use in producing hydrocarbons from a subterranean reservoir located beneath a body of water is disclosed. The well system is intended for use in conjunction with a bottom-founded offshore platform. The inventive well system eliminates the conductors traditionally used in offshore platform well systems. According to the invention, a subsea guide template and an outer casing string extending downwardly from the guide template to a first predetermined depth less than the depth of the reservoir are installed prior to installation of the offshore platform. Thereafter, the platform and the first intermediate casing string are installed, in either order. Drilling for the first intermediate casing string takes place in the open hole defined by the outer casing string with all returns of drilling fluid and drill cuttings occurring at the seafloor. Preferably, the in-water portion of the first intermediate casing string serves as a removable drilling riser for conducting all subsequent drilling operations. The well is then completed in the conventional manner. The present invention may advantageously be combined with pre-installation of some or all of the platform's foundation piles to provide the added benefit of achieving a 'storm-safe' condition in a matter of a few hours.

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First Claim