Matterhorn Export Pipeline And Steel Catenary Riser Design, Fabrication, And Installation
Authors: Jefferies A.T. , Desalos A.P. , Van Der Linden C. 
Published: October 2008

This paper discusses the project planning and execution for the fabrication, installation, and commissioning of the Matterhorn export pipelines including the Steel Catenary Risers (SCR's). Further technical details relating the SCR design issues are provided in OTC paper 16612

The Matterhorn export system consists of a 10" nominal gas line and an 8" nominal oil line both departing the Matterhorn TLP via Steel Catenary Risers. The use of SCR's in a field development is not unusual, however matching platform interfaces, environmental conditions, combined with the reeled installation method identified and represented a number of challenges.

The Matterehorn SCR and pipeline project was challenged by schedule and mechanical interfaces with a host facility that was awarded under an EPCI contract with penalty based milestones for delivery of hardware and installation schedules. The interfaces were further complicated by the need to consider up to six future risers and four future umbilicals in the interface and interference design for the system.

Contracting strategy played a key role in the project execution requiring the project team to manage numerous interfaces while ensuring that warranty provisions by the involved contractors remained protected.

The SCR's and pipelines were installed successfully and have performed as predicted in the early months of operation.

Introduction

The Matterhorn TLP is located in Mississippi Canyon Block 243 which is 100% operated by TOTAL. The gas export line is owned by TOTAL and is tied in to El Paso's VKGS line 15 miles away in MC-20 with a diver installed 10" × 20" hot tap assembly in a water depth of 520'. The 8" oil export line is owned by Chevron Pipeline (CPL) and is connected to their 10" oil transmission line in a water depth of 750ft in South Pass Block 50, again using a diver installed hot tap assembly. The general arrangement for the development is shown in Figure 1.

The TOTAL Matterhorn TLP execution was awarded to Atlantia Offshore as an EPCI contract. The pipelines were not included in this EPCI contract but were managed directly by TOTAL. Because one of the export lines was owned by CPL, and CPL had previous project experience with SCR design and installation, it was decided to form a joint team between TOTAL and CPL for the entire pipeline project execution.

The joint project team approach offered a number of advantages including a common design basis, common clashing analysis and common interface management. The project team organization is shown in Figure 2. The initial project schedule for the pipeline related tasks is shown in Figure 3.

The establishment of the joint export pipeline team postdated the award of the EPCI contract which, as regards to the riser interface data, was based on early project conceptual design work. Essentially:Riser countRiser locationsRiser maximum static top tensionsDynamic amplification factorsDeparture anglesRiser sizes These data are shown in Table 1. The fast track project planning required detailed load information to be provided to the hull designers as early as November 2001 and delivery of SCR receptacles at the hull fabricator by July 2002.