Canyon Express Commissioning and Start-up Experience
Authors: Hare Simon , Case Richard 
Published: October 2008

The Canyon Express project involves a commingled tieback of three dry gas fields, owned and operated by different companies, through a jointly owned twin 12" flowline tieback to a third party host platform at 56 miles distance. It is also the world's deepest development at 2200 m/7200 ft. Design rate is 500 mmscfd.

In the design/construction phase of a challenging project such as Canyon Express, a project team attempts to identify what operational challenges will be faced and how they are to be designed for and managed. The start-up and operational phases show how well anticipated problems have been managed, and bring to light unexpected problems.

This paper presents an overview of the key operational problems anticipated in the Canyon Express project design phase, and whether they did actually occur during and after start-up. It will also discuss the operational experience gained during the commissioning and early production life phases, and the unexpected problems that arose.

Operational Experience Discussed

Flowline dewatering and pigging Flow assurance strategy & hydrate prevention Pipeline liquid inventory management Methanol recovery system and methanol inventory Management Flowline solids production Subsea methanol filter blockages

Significance of Subject Matter.

The depth and tie-back distance of the Canyon Express fields pose significant flow assurance and other operational challenges. The operational experience gained in this development are valuable lessons learned for the development concepts and operating strategies of future long distance, deep water subsea tie-backs.

Introduction

The Canyon Express system is a joint development of three Gulf of Mexico deep water gas fields: King's Peak, operated by BP Americas, Inc.; Aconcagua, operated by TotalFinaElf E&P USA, Inc.; and Camden Hills, operated by Marathon Oil Company. The three fields are located in 6500' to 7200' of water, and are tied into the Canyon Express pipeline system operated by TotalFinaElf. The pipeline system consists of 57 mile long twin 12" flowlines, a main electro-hydraulic umbilical system, and a 2-7/8" diameter single methanol distribution line (SMDL).

The King's Peak field comprises 3 wells, the Aconcagua field 4 wells, and the Camden Hills field 2 wells. The gas produced from the three fields is a very dry gas, containing &gt;99% methane, with up to 0.5% carbon dioxide, and a condensate yield of around 0.75 to 1 bbl/mmscf. The fields jointly have the potential to produce 450-500 mmscfd of gas.

The two 12" flowlines are tied back to a processing platform in 300' of water. This platform, Canyon Station, is owned and operated by Williams Field Services. The subsea control system and methanol injection facilities are also located on Canyon Station. Methanol is stored on Canyon Station in three legs of the structure, the total capacity amounting to approximately 2400 bbl. Methanol is continuously injected at the subsea wells to prevent hydrate formation; injection rates are currently around 800-1200 bbl per day, with a design maximum of 1900 bbl per day. Gas produced from the flowlines is separated from the liquids in two-phase HP separators, then dehydrated in a conventional process prior to export through three separate export lines.