Umbilical Installation

Subsea trees are monitored and controlled via umbilicals suspended in a catenary shape and protected at the splash zones by I- and J-tubes fixed to the structures.

File:Umbilical Reel (Courtesy JDR).png

Umbilical Reel (Courtesy JDR)

File:System Integration Testing of Control Umbilical.png

System Integration Testing of Control Umbilical

File:Umbilical Connecting an FPS to a Subsea Structure.png

Umbilical Connecting an FPS to a Subsea Structure

Requirements for Installation Interface

The installation vessel and its installation equipment should be in good condition and working order, and be verified according to relevant regulations and safety plans prior to vessel mobilization. In addition to the requirement of API Recommended Practice 17I, Installation Guideline for Subsea Umbilical, the interfaces relating to the installation of the subsea umbilical should be carefully managed including these items:

• The design and fabrication of the UTAs and their support frames;
• Determination of the design requirements for all cable crossings;
• The design of umbilical supports for crossing of pipelines;
• Protection requirements.

Installation Procedures

Umbilicals are laid using one of the following typical methods:

• The umbilical is initiated at the manifold with a stab and hinge-over connection or a pull-in/connection method and terminated near the subsea well with a second-end lay-down sled (i.e., infield umbilical connection from manifold to satellite well).
  File:Umbilical Connecting a Host Platform to a Subsea Structure.png

  Umbilical Connecting a Host Platform to a Subsea Structure

The connection between the umbilical and the subsea well is later made using a combination of the following tie-in methods:

(1) rigid or flexible jumper, (2) junction plates, and (3) flying leads.

• The umbilical is initiated at the manifold with a stab and hinge-over connection or a pull-in/connection method. It is laid in the direction to the fixed or floating production system and pulled through an I- or J-tube or cross hauled from the laying vessel to the floating production vessel.
• The umbilical can also be initiated at the fixed or floating production system and terminated near the subsea structure with a second-end umbilical termination assembly (termination head, lay-down sled, umbilical termination unit, etc.). A pull-in and connection tool operated by an ROV may be used to connect the umbilical to the subsea structure.

Umbilical installation can be carried out in the following cases:

• Umbilical installation between subsea manifold and tree;
• Umbilical installation with first-end initiation at subsea structure;
• Umbilical installation with first-end initiation at floater.

Fatigue Damage during Installation

The issues that need to be considered when dealing with fatigue damage during installation of steel tube umbilicals are as follows:

• The contribution to accumulated plastic strain during reeling and potential retrieval; The issues that need to be considered when dealing with fatigue damage during installation of steel tube umbilicals are as follows:
• The contribution to accumulated plastic strain during reeling and potential retrieval;

However, some aspects of installation fatigue analysis do not apply to in-place fatigue analysis:

• Since the umbilical changes configuration and is subject to different loads during various stages of installation, different umbilical models are needed to model the various stages of installation that require analysis.
• For installation fatigue analysis it is appropriate to use a time-domain approach. A frequency-domain analysis would not adequately predict the fatigue damage suffered during installation due to the highly irregular loading that the umbilical experiences during this stage of its life.

References

[1] R.C. Swanson, V.S. Rao, C.G. Langner, G. Venkataraman, Metal Tube Umbilicals- Deepwater and Dynamic Considerations, OTC 7713, Offshore Technology Conference, Houston, Texas, 1995.

[2] International Standards Organization, Petroleum and Natural Gas Industries, Design and Operation of Subsea Production Systems, Part 5: Subsea Umbilicals, ISO 13628-5, (2009).

[3] Technip Technology and Teamwork Achieve World Class Success for Shell Perdido, Oil & Gas Journal on line, Volume 108 (Issue 31) (April 1, 010). http://www.ogfj.com/ index.

[4] N. Terdre, Nexans Looking beyond Na Kika to Next Generation of Ultra-deep Umbilicals, Offshore, Volume 64, Issue 3, Mar 1, 2004, p://www.offshore-mag. com/index.

[5] O. Heggdal, Integrated Production Umbilical (IPU for the Fram Ost (20 km Tie-Back) Qualification and Testing, Deep Offshore Technology Conference and Exhibition (DOT), New Orleans, Louisiana, 2004, December.

[6] Det Norske Veritas, Submarine Pipeline Systems, DNV-OS-F101, (2007).

[7] Det Norske Veritas, Fatigue Strength Analysis of Offshore Steel Structures, DNV-RPC203 (2010).

[8] J. Hoffman, W. Dupont, B. Reynolds, A Fatigue-Life Prediction Model for Metallic Tube Umbilicals, OTC 13203 (2001).

[9] W.K. Kavanagh, K. Doynov, D. Gallagher, Y. Bai, The Effect of Tube Friction on the Fatigue Life of Steel Tube Umbilical RisersdNew Approaches to Evaluating Fatigue Life using Enhanced Nonlinear Time Domain Methods, OTC 16631, Offshore Technology Conference, Houston, Texas, 2004.