Na Kika Umbilical Transport & Installation Challenges
Authors: Clausing K.M. , Williams V.T. , MacFarlane J.C. 
Published: October 2008

The umbilical infrastructure for the Na Kika Development is comprised of four dynamic umbilicals from the host platform and five static umbilicals between subsea fields to provide injection chemicals, power and communication services to five subsea fields. An additional umbilical was also installed to tie back a sixth field, Coulomb, to the Na Kika host.

Shell contracted directly with the installation contractor for transportation and installation of 123km of steel tube umbilicals. A hybrid transportation solution was adopted and multiple lay spread configurations were employed. The campaign marked the largest and most complex umbilical installation campaign undertaken by Shell in the GoM and the first installation of lazy wave umbilical risers from a floating host.

A rigorous approach was applied during the planning phase in order to identify and reduce the risks associated with the novel installation aspects. Contingency plans were prepared and key equipment procured to minimize schedule impact in the event of installation delays or damage. The risk mitigation measures employed, the difficulties encountered and the lessons learned during the installation campaign are expanded in the paper.

Introduction

Execution of the umbilical scope for Na Kika represented a contractual challenge as well as a technical challenge. The numerous novel installation requirements were augmented by the complexities and constant interface evolution inherent with a new green field development project of this magnitude. The nine umbilicals for the Na Kika subsea development and the single umbilical for the Coulomb development were transported from Norway to the Gulf of Mexico during April and August 2003. Installation of the umbilicals was performed during September and October 2003 by the MSV Toisa Perseus using three different lay spread configurations. A selection of highlights and difficulties encountered during the campaign are presented, concluding with some of the main lessons learned.

Umbilical Configuration

All Na Kika umbilicals and the Coulomb umbilical were manufactured with varying quantities of three core materials - zinc extruded carbon steel tubes, zinc extruded Nitronic 19D duplex steel tubes and electric quad cables. All the umbilicals, with the exception of KGL, followed a common construction specification with the carbon steel tubes layed-up in a central bundle and the duplex steel tubes, electric quad cables and fillers layed-up around this central bundle as the second pass. Static umbilicals were jacketed with polypropylene (PP) roving and the dynamic umbilicals were extruded with polyethylene (PE) sheath for the dynamic section only. A summary of dimensional data for the ten umbilicals is presented in Tables 1 and 2. Dry weights are quoted "in air, fluid filled" and submerged weights are quoted "in seawater, fluid filled". Diameters and weights for the dynamic umbilicals are stated for the PE sheathed dynamic section.

Table 1 Static Umbilical Summary (Available in full paper)

Table 2 - Dynamic Umbilical Summary (Available in full paper)

Contract Strategy

A strategy to contract three well-defined scopes; tube supply, umbilical manufacture and umbilical transportation/ installation (T&I) with the project team retaining overall project management was followed.