Field Recovery of High Holding Capacity Anchors in 5,000 Feet of Water

Abstract

This paper will review the engineering design and field procedure for recovery of high holding capacity anchors on a moored drilling vessel in 5,000 feet of water.It will discuss the variables that field personnel can control at the surface and how changing these variables affects forces applied to anchors embedded into a silty-clay bottom. The paper will show how to estimate the resultant force applied to the anchor since there is currently no method available to measure forces at the anchor. The paper will include a discussion of the upgrades to the chain chaser system and a large 450 MT winch used on one anchor handling vessel. This paper will show how to balance line tensions between the winches on a moored drilling vessel and an anchor handling vessel so that the upward resultant force at the embedded anchor is effectively applied. The pulling procedure can result in lower chase wire tensions at the stern of the anchor handling vessel while reducing the time necessary to recover an embedded anchor. Lower wire tensions increase the factor of safety for the components that make up the chain chaser system and reduce the risk of a failure.As operators move to deeper waters using moored drilling vessels, thorough understanding of the forces being applied to the ~hain cha~er and anchor can improve recovery of high holdmg capaCIty anchors and minimize recovery time. This new technology can help moored drilling vessels operate efficiently in deep water.

Deepwater Rig Anchoring: Key Lessons Learned and Ways Ahead

“…This come from the high stresses during decking (insert method) but also when chasing back at the anchor (all methods). Particularly, chaser rings are often inadequately designed (see [3]). …”