The Castorone pipe laying vessel will be used for installing the gas pipeline for the project. Credit: Saipem SpA.
The Argo and Cassiopea fields will produce from four wells that will be tied back to the new Prezioso K platform. Credit: Vismar UK/
The gas produced by the two fields will be processed at a new gas processing plant being built in Gela. Credit: Valerio De Carlo/Wikimedia Commons.

The Argo and Cassiopea fields are located 25km offshore of Italy’s Sicilian coast in the Ibleo Area.

The fields are jointly owned by Eni, an oil and gas company, and Energean, a hydrocarbon exploration and production company, with 60% and 40% interests, respectively. Energean’s 40% interest in the fields was earlier held by Edison E&P, an oil and gas production company that was acquired by the former in 2020.

The project will be Italy’s largest greenfield gas development and is expected to have a net-peak production of 100,300 barrels of oil as an equivalent per day. The two fields will be the main producing fields in the country once operational in 2024.


The Argo and Cassiopea fields lie in the licensed Ibleo Area located within the Strait of Sicily. The area also includes several other prospects such as Gemini, Centauro, and Vela.

Discovery and Geology

The Cassiopea field was discovered by the Cassiopea 1 well in July 2008 at a water depth of 560km, 22km offshore the coast of Agrigento.

The Argo field was discovered in May 2007 by the Argo 1 well in water depths between 1,350m and 1,520m. The well flowed at the rate of 769 cubic feet per day during test production.

The field reservoirs’ holding gas is of the early Mesozoic to Cenozoic Age in the Pleistocene-Age clastic sediments.


The proven and probable gas reserves at the two fields are estimated at 31 million barrels of oil equivalent (mboe).

Gas reserves at the Cassiopea field are estimated to be approximately 16 billion cubic metres.

Argo and Cassiopea Gas Fields Development Details

The fields are planned to be developed through four subsea wells, comprising two new wells and two re-completions. The Argo field will produce from a single well, while the Cassiopea field will produce from three wells.

The four wells will be tied back to the new Prezioso K platform, planned to be installed at a water depth of 45m along with an optimised subsea production system. The platform will host the treatment and compression system for the project and will be connected to the existing Prezioso platform through a 60m-long bridge.

The wells’ control system operations and chemical injection for the fields will be provided from the Prezioso platform. The natural gas produced by the offshore platform will be transported through a new 60km gas pipeline with a 14in diameter installed at a maximum depth of 660m to a new onshore treatment and compression plant being constructed in the reclaimed area of the Gela refinery.

Gas Processing

A memorandum of understanding (MoU) was signed between Eni and the Ministry of Economic Development to transform the Gela refinery area into a green refinery project in November 2014.

The gas produced from the fields will be treated at a new treatment plant being constructed at the Gela refinery area, as part of this MoU.

The construction of the treatment plant started in September 2021 with an estimated investment of more than €700m ($764m). Gas production from the plant is expected to start in the first half of 2024.

The development plan for the treatment plant is aimed at minimising the surface area occupied, maintaining environmental sustainability, and enhancing the local area.

Contractors Involved

Eni Mediterranea Idrocarburi, a subsidiary of Eni, awarded a €300m ($327.41m) contract to Saipem,
The contract is related to the transportation and installation of the offshore gas pipeline connecting the four wells of the Argo and Cassiopea fields to the Sicilian coast. The gas pipeline will be installed by the Castorone and Castoro 10 pipe-laying vessels, while the Saipem 3000 vessel will install the umbilicals connecting the Cassiopea wells to the Prezioso platform.

Proeco, an engineering company based in Italy, was contracted to perform process, mechanical, and machine engineering as well as 3D modelling for the Prezioso K platform.

Arighi Engineering Services, an engineering company based in Italy, was subcontracted by Proeco for architectural front-end engineering design endorsement of the Prezioso K platform topside modules.

Other Development Projects in the Strait of Sicily

The Argo and Cassiopea gas fields are part of the current phased offshore gas development in the Strait of Sicily extending up to the early 2040s. The phased development includes the low-risk Gemini and Centauro fields that hold recoverable resources of 9.7mboe. The two prospects are planned to be drilled in the same campaign as the Argo and Cassiopea fields.

Vela is another well-defined exploration prospect in the Ibleo block, which has a probability of 73% geological success. It is estimated to hold an additional 148 billion cubic feet (bcf) of recoverable gas.

The Ibleo exploration block also includes the Lince oil exploration prospect, which is estimated to hold stock-tank oil initially in place of 1.2 billion barrels.

The Argo and Cassiopea gas fields development plan does not consider the initial gas in place, but the further development phase planned after the development of Gemini, Centauro and Vela is anticipated to extract a further 141bcf of gas.

The fields will be developed through tie-ins to the Argo and Cassiopea gas fields infrastructure and will also include other discoveries in the area, such as Panda and Panda West.