Mooring an Ocean Victory Class MODU on a Pre-laid Mooring in 3,200 Feet of Water at Green Canyon 254

Abstract

WOPyrIGM 19% OFFSHORE TECHNOLOGY CONFERENCE nw$ papaf was pmpafad w pfesenlabm al ha Offshore Techc@Y Confererca kkl m HwstcfI, Texas, 6-9 May 19% TM papa was salauad for presantalm by an OTC Prcgmm Commit-folknwng rav!ew c+ mlcwnattof ontaned m an abstracl submrtted by the autkf(s) Ccmtents of the P&PC as wwanmd me nol been revwed by the OIWWe T@WWWY @ WE S* tO W*M by U-m author(s) The materkl as presmtad tis nd recassaniy rafkd my POsrbcn ot ttw 0iT5P0re TechmMgy Ccdarenm c+ m o%cm PanmssIwI to cmpy @ feemchd to an Astrad d nd mcfe man 303 words lllustfat~s may cot b-a copwd TM *SW sti cmiam CZXMPKUMIS aduwu-ent of~re and by whom W p-ape IS pfesanted AbstractAn Operator wanted to drill one or two additional delineation wells in 3,200 feet of water at Green Canyon 254. Because there were no MODUs capable of this water depth available to fit the Operator's schedule, the Operator elected to increase the water depth capability of an existing Ocean Victory Class MODU. The modification consisted of increasing the number of riser tensioners, installing longer BOP control hoses, guidelines and television cable, and using pre-laid moorings to enhance the mooring capability. This paper describes the pre-laid mooring procedures. Each prelaid mooring leg consisted of one 10 metric ton anchor, 1,000 feet of ground wire, 2,500 feet of dip-zone chain and 3,@30 feet of catenary wire. Prior to the arrival of the MODU, each leg also had 3,500 feet of 2 inch riser wire and a surface buoy. The moorings were laid using a single 6,140 brake-horsepower, anchor-handling, towing, supply vessel with a large A-frame at the stern. This same vessel was used to connect the chain from the MODU to the pre-laid moorings.Using pre-laid moorings to extend water depth capability gives the Operator greater flexibility in selecting MODU'S for deep water drilling and can solve scheduling problems. The use of an A-frame and a ground wire adjacent to the anchor allowed use of a smaller vessel than would otherwise be required. The MODU can be moved to nearby deepwater locations without fully recovering the pre-laid moorings.This operation demonstrates that the water depth capability of an all chain MODU, normally capable of 2,000 feet of water, can lx. extended to over 3,000 feet by using wire inserts and pre-laid moorings.

Deepwater Rig Anchoring: Key Lessons Learned and Ways Ahead

“…New technology arising, such as synthetic ropes and vertically loaded anchors, as well as preset mooring operations tend to push the limitation to much larger depths [1,2]. These issues are dealt with in the second part of this paper : Firstly, last information from a large scale test of a polyester rope on the SEDCO 700 is presented.…”