Multiple anchors for a tension leg platform

摘要

Apparatus and methods are provided for installing an underwater anchor system including a plurality of separate anchors for a tension leg platform. A cluster of tethering elements is connected between the tension leg platform and each of the separate anchors. Each anchor assembly includes a primary anchor which is first located approximately in a desired position upon the ocean floor. This position includes a lateral location and/or an angular orientation about a vertical axis. Then the position of the primary anchor is ascertained and compared to a desired position of the main anchor. The main anchor is designed to be lowered into engagement with the primary anchor. A relative position determining structure is interconnected between the primary and main anchors for varying the relative position of the main anchor relative to the primary anchor to correct for any difference between the ascertained final position of the primary anchor and the desired position of the main anchor. This relative position determining structure is adjusted as necessary. Then the main anchor is lowered into engagement with the primary anchor so that a location and final angular orientation of the main anchor is determined by the relative position determining structure upon engagement of the main anchor with the primary anchor.