Method and apparatus for conversion of semi-submersible platform to

Abstract

A method of conducting offshore well operations including exploration drilling and production from a single floatable platform which is converted from semisubmersible exploration mode to tension leg production mode at a well site. A method of conversion of platform from catenary mooring mode in which exploration and drilling operations are conducted from the platform in semisubmersible mode at the well site to establish production capabilities and upon determining the well site should be produced to tension leg mode for production including the steps of, preparing to conduct production operations in tension leg mode by lowering and setting anchor pile guide means carried by the platform at selected anchor locations, shifting the platform in semisubmersible mode for drilling at each anchor pile guide means, setting permanent anchor pile members in the sea floor at the anchor pile guide means, connecting a tension leg means to the anchor pile members and to said platform, initially tensioning said tension leg means to a selected tension, then releasing said platform from said catenary mooring mode, and further tensioning said tension leg means for operation of said platform in tension leg production mode. A mobile offshore marine platform for conducting exploratory drilling operations in semisubmersible catenary anchor mode and for conducting production activities in tension leg production mode wherein conversion means includes anchor means carried by the platform, means on the platform for installing the anchors while the platform is in catenary anchor mode and tension leg means for interconnecting the anchor means and the platform.