Troll gas field

Troll gas field. Located in the North Sea on the Norwegian continental shelf, it is one of the largest offshore gas fields ever discovered. Operated by Equinor, the field is a cornerstone of Norway's petroleum industry and a critical supplier of natural gas to Europe. Its development required pioneering engineering, including the massive Troll A platform, one of the tallest structures ever moved.

Discovery and development

The field was discovered in 1979 by the Shell group, with the wildcat well 31/2-1 striking significant hydrocarbon reserves. The discovery was confirmed by subsequent appraisal drilling, revealing a colossal structure spanning Blocks 31/2, 31/3, 31/5 and 31/6. Development planning was a monumental challenge due to the field's shallow gas cap over a thin oil column. The Norwegian Ministry of Petroleum and Energy approved the Troll Phase I development in 1986, focusing initially on the gas reserves. The Troll A platform, a concrete gravity base structure, was constructed in Vats and towed to location in 1995, marking a historic feat in offshore construction.

Geology and reserves

The field lies within the prolific Viking Graben in the northern North Sea, approximately 80 kilometres west of Bergen. The main reservoir is the Upper Jurassic Sognefjord Formation, a high-quality sandstone deposited in a shallow marine environment. The structure is a large fault block sealed by overlying Cretaceous shale. Original recoverable reserves were estimated at about 1,325 billion standard cubic metres of gas and 415 million cubic metres of condensate and oil. The thin, roughly 22-metre thick oil leg, known as the Troll West Oil Province, presented a unique recovery challenge, leading to the later Troll Phase II and Troll Phase III projects.

Production and infrastructure

Gas production began in 1995 from the Troll A platform, with gas exported via the Zeepipe pipeline system to Zeebrugge in Belgium. The Troll B and Troll C semi-submersible platforms were installed to develop the oil province, with production starting in 1995 and 1999, respectively. Oil is transported via the Troll Oil Pipeline I and Troll Oil Pipeline II to the Mongstad refinery. The field is also a hub, processing gas from the nearby Kvitebjørn and Visund fields. Advanced technologies like horizontal drilling and subsea completions are extensively used, particularly for the oil zone.

Economic and environmental impact

The field is fundamental to the Norwegian economy, contributing vast revenues to the Government Pension Fund of Norway. It supplies a significant portion of Europe's natural gas, enhancing energy security for countries like Germany, France, and the United Kingdom. Environmental considerations have been integral, with measures to reduce flaring and carbon dioxide emissions. The installation of the Troll A platform on the seabed created an artificial reef, studied by marine biologists from the University of Bergen. The field's operations are regulated by the Norwegian Petroleum Directorate and the Ministry of Climate and Environment.

Ownership and partnerships

The field is owned by a consortium of major energy companies under a production licence. The current licensees, with their respective interests, are Equinor (30.58%), the state's direct financial interest represented by Petoro (56%), Shell (8.10%), TotalEnergies (3.69%), and ConocoPhillips (1.62%). The partnership is governed by a joint operating agreement, with Equinor serving as the technical service provider and operator. The license was originally awarded in the fourth Norwegian licensing round and is subject to the framework of the Norwegian Petroleum Act.

Category:Natural gas fields in Norway Category:North Sea oil fields