Assessment of undiscovered oil and gas resources of the West Siberian Basin Province, Russia, 2008

Introduction

The U.S. Geological Survey (USGS) recently assessed the undiscovered oil and gas potential of the West Siberia Basin Province in Russia as part of the USGS Circum-Arctic Resource Appraisal program. This province is the largest petroleum basin in the world and has an areal extent of about 2.2 million square kilometers (fig. 1). It is a large rift-sag feature (fig. 2) bounded to the west by the Ural fold belt; to the north by the Novaya Zemlya fold belt and North Siberian Sill, to the south by the Turgay Depression and Altay-Sayan fold belt, and to the east by the Yenisey Ridge, Turukhan-Igarka uplift, Yenisey-Khatanga Basin, and Taimyr High (fig. 1). The West Siberian Basin Province has a total discovered oil and gas volume of more than 360 billion barrels of oil equivalent (Ulmishek, 2003). Exploration has led to the discovery of tens of giant oil and gas fields, including the Urengoy gas field with more than 350 trillion cubic feet of gas reserves and Samotlar oil field with reserves of nearly 28 billion barrels of oil (Ulmishek, 2003). This report summarizes the results of a reassessment of the undiscovered oil and gas potential of that part of the province north of the Arctic Circle; a previous assessment that included the entire province was completed in 2000 (Ulmishek, 2000). The total petroleum system (TPS) and assessment units (AU) defined by the USGS for the assessments in 2000 were adopted for this assessment. However, only those parts of the AUs lying wholly or partially north of the Arctic Circle were reassessed for this study.

Geologic Definition of Assessment Units

Ulmishek (2000) defined the Northern West Siberian Mesozoic Composite TPS in the northern part of the West Siberian Basin Province (fig. 1). More than 70 fields have been discovered in this TPS, most of which are gas fields. Several rock units might be potential source rocks, including strata of Jurassic and Cretaceous age. However, the true source of the gas resources remains unknown (Ulmishek, 2003).

Two AUs encompass the northern part of the province (fig. 1). The Northern West Siberian Onshore Gas AU includes primarily Cretaceous sandstone reservoirs in structural traps. The South Kara Sea Offshore AU, considered to be the offshore geologic extension of the Northern

West Siberia Onshore Gas AU, includes similar traps and reservoirs. Each AU was evaluated in its entirety for undiscovered, technically recoverable, oil and gas resources, but the assessment results reported here are only for those parts that are north of the Arctic Circle. About 75 percent of the Northern West Siberian Onshore Gas AU is north of the Arctic Circle, and the South Kara Sea Offshore AU lies wholly within the Arctic Circle (fig. 1).

Resource Summary

The results of the quantitative assessment of undiscovered, technically recoverable, conventional oil and gas resources in that part of the Northern West Siberian Mesozoic Composite TPS north of the Arctic Circle are given in table 1. The total estimated means for undiscovered conventional oil and gas resources are 3,659 million barrels of oil (MMBO), 651,499 billion cubic feet of natural gas (BCFG), and 20,329 million barrels of natural-gas liquids (MMBNGL). Of these volumes, the Northern West Siberian Onshore Gas AU accounts for 1,152 MMBO, 29,277 BCFG, and 850 MMBNGL, and the South Kara Sea Offshore AU accounts for 2,507 MMBO, 622,222 BCFG, and 19,479 MMBNGL. The estimate for undiscovered gas in the South Kara Sea AU reflects the exploration immaturity compared to the Northern West Siberian Onshore Gas AU.

Figure 2. Line of cross section A-A´ in the West Siberian Basin Province; location of section shown in figure 1. J, Jurassic; K1b, Berrasian; K1v, Valanginian; K1g, Hauterivian; K1br, Barremian; K1a, Aptian; K1al, Albian; K2c, Cenomanian; K2t, Turonian; Pg1, Paleogene; Pg2-3, Eocene-Oligocene; Q, Quaternary. b.s.l., below sea level. From Ulmishek (2000).

References

Ulmishek, G., 2003, Petroleum geology and resources of the West Siberian Basin, Russia: U.S. Geological Survey Bulletin 2201–G, 49 p.

Ulmishek, G., 2000, West Siberia Basin—Geologic Province 1174, in U.S. Geological Survey World Energy Assessment Team, U.S. Geological Survey World Petroleum Assessment 2000—description and results: U.S. Geological Survey Digital Data Series DDS–60, four CD–ROM set, Disk 2.

For Further Information

Assessment results are available at the USGS Energy Program Web site, http://energy.usgs.gov/arctic, or by contacting Donald L. Gautier, Task Leader for the USGS Circum-Arctic Oil and Gas Resource Appraisal (gautier@usgs.gov).

West Siberian Basin Province Assessment Team:

Christopher J. Schenk, Kenneth J. Bird, Ronald R. Charpentier, Donald L. Gautier, David W. Houseknecht, Timothy R. Klett, Thomas E. Moore, Mark J. Pawlewicz, Janet K. Pitman, and Marilyn E. Tennyson.

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