Mexilhão

Location and Geology

The Mexilhão gas field is located in the Santos Basin, off the coast of São Paulo, Brazil, approximately 160 km offshore. The field is situated in water depths ranging from 320 meters to 550 meters.

Discovery and Development

The Mexilhão field was discovered in 2003 by Petrobras, making it one of the largest gas fields discovered by the company in Brazil at that time. Development drilling began in 2005, although initial drilling activities were challenging due to high downhole vibration caused by hard sandstone formations and the field's high temperatures (over 130°C at the well heads) and working pressures (10,000 psi).

Infrastructure

The development of the Mexilhão field is centered around the fixed gas production platform PMXL-1. This platform is the largest offshore metallic structure ever erected in Brazilian waters, standing 230 meters tall and weighing approximately 12,000 tons for the topside and 10,500 tons for the jacket. The platform is secured to the seabed using 3,150 tons of tubular steel piles up to 120 meters long. The topside includes a natural gas production plant designed to process 15 million cubic meters of gas per day and 3,200 cubic meters of condensate daily.

Subsea and Pipeline System

The produced gas is conveyed through submarine pipelines to the shore-based gas processing plant, specifically the Monteiro Lobato Gas Treatment Unit (UTGCA) in Caraguatatuba, São Paulo state. The gas is then forwarded to the national pipeline grid. The subsea system includes two umbilicals, each around 22 km long, running from the platform to a manifold at a depth of 500 meters, and seven additional umbilicals totaling nearly 15 km, connecting the manifold to the seven well heads.

Pipeline Connections

The Mexilhão field is connected to a broader pipeline network. The Tupi–Mexilhão gas pipeline, operated by Petrobras, Shell, and Galp Energia, is a 248 km long pipeline that starts in Rio de Janeiro and ends in São Paulo. This pipeline is part of a larger network that includes the URG–Mexilhão and PMXL–UTGCA pipelines.

Installation and Contracts

The installation of the PMXL-1 platform was scheduled for December 2009, with Petrobras closing a $70 million contract with Saipem for the installation. Acergy was awarded a contract valued at approximately $400 million for the installation of a 120 km long, 34-inch diameter gas export trunkline from the platform to shore, although this project was later classified as a discontinued operation due to the sale of the Acergy Piper.

Production

Production from the Mexilhão field was scheduled to begin in 2010, with an initial output of 12 million cubic meters per day, expected to increase to 15 million cubic meters per day. The field's production is integrated with adjacent areas to achieve this output.

Strategic Importance

The Mexilhão project is of strategic importance as it creates infrastructure that will serve other gas fields already discovered in the region. The total cost of the development was around $1.9 billion.

Processing and Distribution

The gas processed from the Mexilhão field is treated at the Monteiro Lobato Gas Treatment Unit (UTGCA) in Caraguatatuba and then distributed through pipelines to Taubate and further connected to the national pipeline grid, ultimately reaching consumers in São Paulo and other regions.

In summary, the Mexilhão project is a significant natural gas development in Brazil, characterized by its challenging operating conditions, extensive infrastructure, and strategic importance for the region's energy supply.