Neptune Project: Spar History and Design Considerations

Abstract

This peper wes selected for presentetion by the OTC progrem Commillee following review of informetion conteined in en ebstract submilled by the euthor(s). Contents of the peper, es presented, have not been nsviewed by the Offshore Technology Conference end ere subject to correction by the euthor(s). The meteriel, es presented, does not necesserily reflect eny posnion of the Offshore Technology ConIensnce or ns off'lC8I'8, Electronic reproduction, distribution, or storage of eny part of this peper for commerciel purposes without the wriIIen consent of the Offshora Technology ConIensnce is prohibned. Permission to nsproduce in print is nsstricled to en ebstrect of not mora then 300 words; illustrations mey not be copied. The ebstract must contein conspicuous ecknowledgment of whens end by whom the paper wes presented. AbstractNeptune marks the fIrst use of this type of structure to support production operations. The paper will discuss existing spar type structures and the development of the Spar design for the Neptune project. Design considerations for hull sizing and mooring system are discussed. Motion analyses and con-fIrming model tests are presented. The well system design is introduced, which allows for the use of surface type trees providing economical well bore intervention capability. The topsides facility layouts are described. The Spar's capability of future drilling operations, using a semisubmersible drilling rig moored alongside the Spar, is discussed.

Large Floating Structures

“…Instead, the risers were supported on RAM type or ''push up'' tensioners as illustrated in Fig. 6 Schematic of production riser and buoyancy cans (Glanville et al 1997) the rods upwards. Installation of the production riser tensioners in shown in Fig.…”

Modeling Vortex Induced Motions of Spars in Uniform and Stratified Flows

“…Since the installation of the first spar in the Gulf of Mexico [1], the hull shapes have evolved from the "classic" cylinder shape to include "cell" and "truss" configurations [2]. All of these are potentially subject to VIM.…”

“…Reynolds numbers and surface roughness were also varied. The experiments available for comparison here were performed at the MARIN facility in the Netherlands1 in 1:46-scale giving a model spar hull diameter of 0.8m and a draft of 4.26m. It is well established that VIM, if it occurs, tends to be strongest when the natural frequency of vibration of the spar coincides with the vortex shedding frequency or at reduced velocities ( rn U ) of about 6 or 7, which correspond to a Strouhal number ( t S ) of a little less than 0.2.…”

“…The mesh includes all hull appurtenances, except for the anodes. This particular model test, unlike most others,1 Maritime Research Institute Netherlands -Depressurized Towing Tank did not include the hull anodes. Hence the physical model and the numerical model were essentially identical.…”

Floating Offshore Platform Design

“…This was based on providing adequate separation between the wave energy and the natural heave period of the spar so that resonant heave would not be excited (Glanville et al, 1997). This was based on providing adequate separation between the wave energy and the natural heave period of the spar so that resonant heave would not be excited (Glanville et al, 1997).…”