Abstract

The Perdido Development project, in the Gulf of Mexico, has set several record firsts; including, in 4500 feet of water, the first diverless deep-water tie-in to an existing export line and the deepest tie-in to an in-service pipeline system. It is also the first to employ a unitized foundation and prefabricated jumper spool.

Identifying options for transmission of oil and gas production from the deepwater spar facility to shore required innovative thinking and input from many technical disciplines. The options were limited; Perdido is located in an area with little export infrastructure, and the route to shore covers some of the gulf's most challenging terrain. The closest shallow-water platform is over 140 miles from Perdido.

Analysis revealed that the lowest cost option with the most manageable risk was a tie-in to the existing HOOPS export pipeline, approximately 70 miles north of Perdido. However, connecting to an 18-inch, operating pipeline in deep water provided major engineering challenges.

The project required subsea installation of a piggable wye in the HOOPS pipeline to provide a connection point for Perdido. In a clear break with conventional tie-in projects, an innovative new methodology was developed that enabled the Perdido export connection system to be fabricated in its entirety onshore and reassembled on the pipeline using a reference system to ensure a perfect fit.

The objective was to reduce HOOPS shut-in time and return the pipeline to service as safely and efficiently as possible. However, the connection system also had to meet several other criteria: zero release of hydrocarbons and re-configurable, which would provide the flexibility to serve future connection needs.

Six months after the project's spar production platform was put into place, the Perdido subsea tie-in was installed on the seafloor. HOOPS production was interrupted for 17 days in March 2009 to accommodate the connection. Consistent with Shell's commitment to protecting people and the environment, the work was executed with no safety or environmental incidents.

The ability to connect subsea without a pre-existing connection point is an enabling technology available to the industry as it continues to move into ultra-deep water while executing projects far from existing production transportation infrastructure.

Introduction

The Perdido spar is the world's deepest direct vertical-access spar. Moored in a water depth of 7817 feet with flowlines extending to 9790 feet, it will act as a hub for and enable development of three fields: Great White, Tobago and Silvertip. The Perdido Development is a joint venture between Shell (operator), Chevron and BP. Located in Alaminos Canyon blocks 857, 859 and 815 in the western Gulf of Mexico, it supports subsea wells connected to the spar host facility by a system of flowlines and subsea structures.

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