Natural gas production project Carina Aries

Carina Aries, Argentina’s largest offshore gas production project to date, is an important growth driver for our subsidiary in Argentina. The consortium, made up of Total Austral (operator, holding: 37.5 %), Wintershall (37.5 %) and Pan American Energy (25 %) discovered major natural gas deposits around 80 kilometres off the coast of Tierra del Fuego in 1981. 1,668 kilometres of 2D seismology and 1,612 square kilometres of 3D seismology have been carried out. Eight percent of all Argentina's secure and acknowledged natural gas reserves (850 billion cubic metres, as of 31 Dec 2004) have been shown to be there. The intention is to produce around 56 billion cubic metres of natural gas, 3.4 million tonnes of condensate and 2.4 million tonnes of LPG from the Carina and Aries fields by 2007. The main customers for gas production are primarily major cities and industrial centres.

The Carina und Aries fields are located in the province "Tierra del Fuego, Antártida e Islas del Atlántico Sur". Carina was discovered in 1983 by the borehole Carina X1. It is an accumulation of oil and natural gas located approx. 80 km off the coast. Its structure stretches over 890 sq km. The water depth is between 80 and 100 metres. Between 1983 and 1999, 13 test bores were drilled and 2D and 3D seismic explorations were carried out. The deposits in the main strata of the Springhill formation are located at a depth of approx. 1,000 metres. The field has good petrochemical properties. The gas contains little condensate. The Aries field is located 30 km away from the coast of Tierra del Fuego, and was discovered in 1981. The structure stretches over 12 km in length and 4 km in width. The water depth varies between 60 and 80 metres. Between 1982 and 1995, 4 test bores were drilled and 2D and 3D seismic explorations were carried out. The reserves are located in the Hydra and Agro reservoir rocks at a depth of 1,600 metres. The gas from Aries has an even higher condensate content than that found in Carina.

The platforms consist of two main elements: the "jacket", which is attached to the sea floor as the support for the platform, and the "deck". The jackets were developed in Houston and manufactured in the shipyards of Louisiana, in the USA. They were taken on special transporter ships to the installation location at the end of 2003. The Carina jacket is a construction 80 metres in height and 15 metres in width. By comparison, that corresponds approximately to an 18-storey skyscraper. The Aries jacket is 76 metres long and 15 metres wide. The decks were produced in the port of Veracruz in Mexico, and shipped in December 2004.

One of the biggest technical challenges of the project was how to transport the oil and gas from these fields far from the coast of Tierra del Fuego. The solution lies in multiphase transport technology. A network of pipelines over 100 km in length has been installed below the sea level, linking the boreholes to the consortium’s processing plants on the coast. Gas, condensates and water are carried through these pipes without prior separation. As this means that no processing is required on site, the platforms can operate unmanned.

The water temperature on the seabed around the production platforms is approx. 2°C. Almost the entire run of the pipelines is affected by these temperature conditions. Wet gas, which is not separated from the accompanying liquids on the platform, is transported in the pipeline that links the platforms to the processing plants on the coast. For that reason, the wet gas on the platform has to be enriched with MEG (monoethylene glycol), so that no hydrates can be formed which would choke the transport routes. The MEG introduced into the pipelines reduces the freezing point (13° undercooling) and provides protection against corrosion. It is almost entirely recovered during processing of the wet gas on land.

The pipeline to the Carina field is around 80 kilometres in length, and has a diameter of 24 inches. It has been designed to withstand a pressure of 96.5 bar, and has a wall thickness of 15 mm. Each element of the pipeline is 12 metres long, weighs 12 tonnes and has an internal diameter of 60 centimetres. In addition to which, there is an outer coating to protect it against the corrosion that may occur as a result of use in seawater. The Aries pipeline is 18 inches in diameter, and is 21 kilometres long.

he consortium’s processing plants have been expanded and their capacity increased substantially. Additional installations have been developed for Río Cullen, which are suitable for processing a maximum production volume of 14 million cubic metres per day. In addition to which, the gas pipelines between Río Cullen and the Cañadón Alfa natural gas processing plant have been supplemented over a length of 27 kilometres by a new pipeline 24 inches in diameter. This additional pipeline has been designed to transport dry gas, as initial separation takes place at the Río Cullen plant.

The natural gas is transported along the General San Martín gas pipeline, predominantly to major cities and industrial centres.