Diverless lay-away flowline installations in conjunction with first end connections to subsea completions have been successfully installed worldwide in water depths from 330 to 1620 feet (100-493 m). '!his paper reviews the design am operational experience gained from several deepwater subsea layaway completions, pioneered in Brazil, and how this technology has been applied to two recent deepwater subsea completion projects which have extended the technology into guidelineless operations approaching 2500 feet (750 m) am hybrid flowline design (flexible pipe connected to "reeled" steel pipe).
Flexible pipe lay-away completions are defined as a subsea diverless flowline installation technique where a flexible pipe bundle is:
Attached to a flowline hub assembly, then keelhauled between a drilling vessel am a pipelay vessel.
captured in the moonpool am connected to a subsea tree via a vertically oriented hydraulic connector.
Fully functioned am pressure tested with the subsea tree in the moonpool to assure reliable operation once the tree is placed in production. Problems can be diagnosed am mitigated quickly by personnel at the drilling vessel moonpool.
Attached to the tree lowered together down to the prepared subsea well in a pre-planned sequence of tree lowering am bundle payout operations to minimize installation loads.
Structurally latched to a receiver cradle on the subsea wellhead, locking the flowline hub an::l flowline bundle to the subsea well's framework. The only underwater seal connections are those associated with the tree to the well.
The flowlines can be hydraulically unlocked from the tree at the same time the tree is unlocked from the well should the tree have to be retrieved during a well workover. The flowline bundle is left behind as the tree is lifted in a single vertical motion. No prior horizontal motions to back the flowline bundle away from the tree are required. Reconnection the tree to the well am the flowlines is a simple reverse of the disconnect operation. The advantages of the flexible pipe lay-away technique are:
The ability to fully test all flowline am control system connections at the drilling vessel moonpool am quickly fix interface problems.
The time for first em connection operations is combined with the time to test am install the subsea tree, reducing overall project installation time.
The relatively small size of flowline equipment am elimination of elaborate flowline connection runningtools. All flowline connections am test functions are carried out through a tree installation tool.
The tree is retrieved am relanded via a single vertical motion am reconnected to the well am flowline using standard hydraulic connectors. All flowline am control system seals are recovered with the tree and can easily be replaced at the surface.
The disadvantage of the flexible pipe lay-away technique is:
The lay-away operation may require two offshore vessels, often on different contracts and operating schedules, on location at the same time. Planning the logistics and scheduling of both the drilling and pipelay vessels can be extremely difficult
