Jack / St Malo Deepwater Oil Project, Gulf of Mexico

The Jack/St Malo deepwater project comprises the joint development of the Jack and St Malo oilfields in the Gulf of Mexico. The fields are located 40km apart.

Chevron, an oil and gas company based in the US, is the operator and holds 51% interest in the field. Other partners include MP Gulf of Mexico (25%), which is owned by Murphy Oil (80%) and Petrobras America (20%), Equinor (21.5%), ExxonMobil (1.25%) and Eni (1.25%).

The deepwater project was approved by the partners in October 2010. An investment of $7.5bn was made in the initial development phase of the project. The first production was announced in December 2014.

Chevron is currently developing the St. Malo Stage 4 waterflood project to boost production from the field. The first water injection is expected in the second half of 2024.

Project location

The Jack and St. Malo fields are located 280 miles (450km) south of New Orleans offshore Louisiana in the Gulf of Mexico.

The Jack field lies in Walker Ridge blocks 758 and 759 at a water depth of 7,000ft and the St Malo field lies in Walker Ridge Block 678 at a water depth of 2,100ft.

Jack/St Malo oil field discovery details

The St Malo field was discovered in October 2003 by a well drilled by Transocean’s Discoverer Spirit drillship. The well struck a net oil pay of 1,400ft.

The Jack field was discovered in July 2004 by the exploration well Jack-1. The well was drilled by Transocean’s Discoverer Deep Seas drillship to a depth of 29,000ft. It struck 350ft of net oil pay.

Geology and reserves

The Jack and St Malo field reservoirs are located in a geological formation known as the lower tertiary trend. The formation was deposited more than 65 million years ago, 20,000ft below the seabed.

It covers an area larger than 300 miles off the Gulf Coast of the US between Texas and Louisiana. The formation is estimated to contain vast resources for long-life projects of up to 30 to 40 years.

The total recoverable resources of the two fields are estimated at more than 500 million oil-equivalent barrels.

Development of the Jack/St Malo fields

The development of Jack/St Malo fields was carried out in phases. Stage one was completed in 2014, followed by stage two in 2018 and stage three in May 2020.

The initial phases of development involved drilling ten production wells: four at Jack and six at St Malo.

The development also involved drilling 43 subsea wells, which are tied back to the Jack/St. Malo semisubmersible floating production unit.

Stage three included the drilling of two additional wells at the Jack field.

Chevron announced the St. Malo Stage 4 waterflood project in September 2019 to extend the life of the field. It is the company’s first project in the deepwater Wilcox trend and will help in recovering more than 175 million barrels of oil equivalent.

The project includes the drilling of two new production wells, three injector wells and the installation of topside water injection equipment on the floating production facility.

Jack/St Malo fields drilling details

The second well, Jack-2, was drilled at the Jack field by Transocean’s Discoverer Deep Seas drillship in 2005. The Cajun Express semisubmersible was used in 2006 to conduct a production test on the well.

Appraisal drilling commenced at the St Malo field in May 2004. An appraisal well was drilled to a depth of 7,036ft of water in July 2004. The well struck 400ft of net oil pay.

Transocean’s Discoverer Clear Leader was used to drill the wells in the initial phase of development, under a five-year contract that was signed in 2009.

Jack/St Malo semi-submersible floating production facility

The fields are co-developed with subsea completions flowing back to a single host floating semisubmersible production facility, which is installed at a depth of 7,000ft. Its topsides weigh 33,000t and the facility has a capacity of 170,000 barrels of oil per day and 42 million standard cubic feet per day of natural gas making it the biggest of its kind in the Gulf of Mexico.

It acts as a hub for the 43 subsea wells, which are divided into three clusters comprising subsea wells, pumps and other equipment on the seafloor, and are tied back to the facility.

The hull of the production facility was moored, and the topsides and other equipment including piles and tendons were delivered at the offshore location in March 2014. The equipment was carried over Crowley Maritime’s Ocean class tugs.

Pipeline

A crude oil export pipeline is installed from the fields to a processing facility owned and operated by Shell in Green Canyon block 19 (GC19).

From GC19, the crude oil can be transported to refineries on the Gulf Coast.

The pipeline is 220km long with a diameter of 24in and reaches a maximum depth of 2,140m. The Chevron Pipeline Company built and operates the pipeline for the Amberjack Pipeline Company (APC).

APC is a joint venture between Chevron Pipeline Company and Shell Pipeline Company.

Contractors involved

Subsea 7, a subsea engineering, construction and services company, was awarded a subsea installation contract for the St Malo field in December 2019. The scope of the contract includes project management, engineering, construction and installation of a multiphase pump system at the St Malo field and a 22km water injection flowline system.

In January 2010, Cameron, a subsea drilling and production equipment supplier, was awarded a $230m contract to supply subsea equipment and engineering and project management services for the fields. The company also provided 12 subsea trees of 15,000psi, manifolds and related connection systems.

Wood Group, a consulting and engineering company, was awarded a contract to commission the production facility.

Mustang, a subsidiary of Wood Group, was awarded a contract to carry out a detailed design for the topsides of the production facility in September 2010. The company conducted the front-end engineering and design for the facility in 2009.

Saipem, an oilfield services company, won a contract to transport and install the crude oil export pipeline from the fields in December 2010. The company used its pipelayer vessel Castorone to install the pipeline.

In April 2011, McDermott International, an engineering and construction solutions provider, was contracted to fabricate and install subsea equipment including umbilical, jumpers and control systems for the project.

KBR, a technology and engineering solutions provider, won a contract in April 2011 to provide detailed design services for the Jack/St Malo production facility. The work included design and engineering services for the hull, accommodation facilities, mooring system and other facilities.

In May 2011, Chevron contracted Aker Solutions, an oil and gas production solutions provider, to supply a subsea umbilical for the project.

Optical Metrology Services, a pipe inspection and measurement services company, provided dimensional measurement services for pipes used for the project.

Danos, an energy service provider, delivered hook-up and commissioning services for the Jack/St Malo project.