East Barents Basin is located in the east of Barents Sea, bordering Xindi Island in the east, along the northern coast of Russia in the south, surrounded by Svalbard Islands and Franz Josef Islands in the north, and bordering the Middle Barents Platform in the west. The western edge of the basin is located in the sea area bordering Norway and Russia, with a total area of about 53.5× 104km2 (Figure 6- 1).

The basement of the basin is mainly Precambrian metamorphic rock basement, which is composed of Lake Baikal and Caledonian fold rock series. The thickness of sedimentary caprock is 20km, which mainly includes two sets of rock series: the lower part is passive marginal deposits in the western Ural Ocean from late Devonian to early Permian, mainly carbonate rocks and shale deposits; The upper part is terrigenous clastic rock, which belongs to Late Permian-Quaternary strata.

The main body of the basin is characterized by rift structure, especially in the middle of the basin, where the granite-metamorphic crust becomes thinner or even disappears. The Late Permian-Late Triassic was a stage of rapid activity due to strong rifting. Post-rift subsidence continued until Jurassic, and a large number of debris from the Eastern Urals Mountains were deposited. The change of Oligocene plate movement pattern led to the structural inversion of the whole Arctic region, which in turn led to the evolution of passive margin and glaciation.

According to the characteristics of caprock, the East Barents Sea Basin can be divided into the South Barents Sea Depression and the North Barents Sea Depression (Figure 6- 1), with Tokman-Luninglong as the boundary. At the junction of syncline of East Barents Plateau and Xindi Island Uplift, a compressive Xindi Island foreshore is divided, and a series of narrow local uplifts extending parallel to Xindi Island are distributed in the south. Through oil and gas exploration, a series of quite large oil and gas fields have been discovered, among which the largest are Tokman Hof gas field, Rudrov gas field and Arctic gas field.

Figure 6- 1 Distribution and profile position of East Barents Sea Basin

Second, the course of oil and gas exploration

After nearly 20 years of exploration, the East Barents Sea Basin has been proved to be a new oil and gas area with great exploration prospects. According to the current exploration results, the basin is dominated by natural gas production.

The exploration of the East Barents Sea Basin began in the 1960s, when the Soviet Union conducted a series of regional geophysical surveys, including gravity, shipboard and airborne magnetic surveys, seabed geological surveys, seabed sampling, environmental and geochemical studies, etc.

From 1978, the North Offshore Oil Geophysical Company of the Ministry of Natural Gas Industry of the Soviet Union undertook seismic survey, and reached the peak of seismic exploration at 1990, with a total length of 38307km. By the end of 1999 and 1, the cumulative length of 2D seismic lines in Barents Sea and Bo Chara Sea reached 333300km, including 8 1000km of seismic survey data, 0/65000 km of seismic survey data and 87000km of detailed seismic survey data. In Barents Sea Basin, 39 forecast targets and long-term targets are circled.

At the end of the 20th century, major breakthroughs were made in parametric drilling in Flanders, Josef Land and Svalbard Islands, with a maximum depth of 3,526 meters ... The discovery of onshore oil and gas in Russia's Timan-Bojola Basin promoted the exploration of Bojola Sea in the early 1980s and quickly spread to the South Barents Sea. Offshore drilling started at 198 1, and 1983 broke through for the first time, and Murmansk gas field was discovered. Then the North Kilding gas field was discovered at 1984. The reservoirs of these two gas fields are sandstone of Lower-Middle Triassic.

Tokman gas field, discovered in 1988, is one of the largest offshore gas fields in the world. It is estimated that its recoverable reserves are 87 TCF (2.44×1012m3). The gas field contains natural gas and condensate oil from four sets of sandstone reservoirs in the Middle-Upper Jurassic, and the discovery of this gas field greatly increased the oil and gas reserves of the Soviet Union in that year.

In 1990s, two large gas fields, Ludlovskoye and Ledovoye, were discovered in the north of Novo, Tokman, with Jurassic sandstone reservoirs. Up to June 1999 and 1, 22 prospective structures (including 14 in Barents Sea) have been drilled in the Barents Sea and Bo Chara Sea. A total of 43 wells have been drilled, and 33 wells have been drilled. The total drilling footage is127300m (including 90600m in Barents Sea).

In September 2007, the Snohvit gas field developed by Total Company of France was put into production. At that time, it was predicted that the output in 2008 would reach nearly 57× 108m3.

According to incomplete statistics, the actual exploration workload in the East Barents Sea Basin is limited at present, and the average 2D seismic line density is only 0. 12km/km2. There are exploration wells 13, and other exploration wells 17 (table 6- 1). It can be seen that the exploration degree of the East Barents Sea Basin is still very low, which is related to the harsh natural conditions and very weak infrastructure of the basin.

Table 6- 1 Summary of Exploration Degree in East Barents Sea Basin