U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY
The Timan-Pechora Basin Province of Northwest Arctic Russia: Domanik – Paleozoic Total Petroleum System
Baikalian (Riphean-Vendian) basement of the Timan Ridge uplift and the Izhma-Pechora Depression is relatively homogeneous and rigid. Basement in the Pechora-Kolva Aulacogen and regions eastward (Figure 1) changes to that of active margin and transitional crust (Bogatsky and others, 1996), with greater compositional heterogeneity that resulted in repeated fault activation and structural inversion through time. Thus, the Pechora-Kolva Aulacogen and the Adzva-Varandey Zone (also a possible aulacogen) contain shallow structures discordant with those at basement level (Figure 1 and Figure 2b). Old aulacogen borders are marked with shallow anticlines known as the Pechora-Kozhva, Shapkino-Yuryakha, Kolva, Sorokin, and Chernov Swells. The Lay and Bolshezemelsk basement arches are masked by overlying shallower basins (Denisov and Khoreyver Depressions, respectively). Basement crops out in the Timan Ridge and Ural Mountains, but attains 12-14 km depths in eastern foredeep basins bordering the western side of the Ural and Pay-Khoy / Novaya Zemlya fold belts.
After latest Proterozoic plate collision (post-Riphean, pre-Vendian "Baikalian Orogeny"), the Timan-Pechora region was a passive continental margin for much of the following Paleozoic era, with episodes of Ordovician and Devonian rifting (Driscole and Golden, 1995; Dedeyev and others, 1996; Sobornov and Rostovshchikov, 1996; Ismail-Zadeh and others, 1997) (Figure 3). Paleozoic cratonic landmasses were to the west-southwest, with the Uralian Ocean to the east-northeast. Earliest Paleozoic basin fill gradually changed from siliciclastic- to carbonate-dominated. Upper Ordovician evaporites were deposited in the eastern parts of the province (Tarbayev and others, 1991; Stepanova, 1994).
Significant Middle Devonian aulacogen rejuvenation (Pechora-Kolva, possibly Varandey-Adzva, Figure 1) was concurrent with basaltic volcanism and the appearance of siliciclastics locally from the west. Eastward prograding, major shelf-edge reef systems bordered elongate, restricted intrashelf basins where rich organic matter was preserved ("Domanik" facies). During the following Carboniferous Period, structural inversions again were associated with localized influxes of siliciclastics and precipitation of evaporites (Lower Carboniferous, Figure 3), but Tournaisian reefs were less extensive than Upper Devonian varieties.
By Permian time, the Hercynian Orogeny brought compression from the east, thrusting slope and deep marine rocks over their shelf counterparts and creating the proto-Ural Mountains and their molasse-filled foredeep basins. Timan-Pechora’s major provenance eventually changed to an easterly sourced, siliciclastic-dominated style. Structural inversions, combined with sea-level fluctuations, resulted in complex facies distributions and periods of erosion. Major Early Permian shelf-edge reefs proliferated, and a subsequently continuous subsidence began in the Barents Sea Basin to the north. Timan-Pechora Triassic and later sedimentation became largely continental in the southern regions.
The Pay-Khoy / Novaya Zemlya fold belt and its foredeep basins were created in Late Triassic to Early Jurassic time (Early Cimmerian Orogeny), post-dating formation of the Ural foldbelt. The compressional eastern boundary of the Timan-Pechora Basin Province was most recently uplifted again in late Tertiary time, but that Neogene deformation was largely restricted to the eastern mountain margin bordering western Siberia (Sobornov and Rostovshchikov, 1996). Overall, the Timan-Pechora Basin is filled with 55-60% carbonates, 35-40% siliciclastics and about 5% evaporites (Dedeev and others, 1994).
Exploration History(Continuedon Next Page)
Over time, the focus of Timan-Pechora oil and gas exploration migrated from the southwestern part of the province – where seeps abound and permafrost is rare – to the northeastern region where the land is swampier and lower in elevation and has year-round permafrost. The entire province is characterized with extreme cold temperatures, and not all fields produce regularly. New joint ventures have been established with Western industry.
The presence of oil near Ukhta in the southwestern part of the Timan-Pechora Basin Province was known as early as 1595, and between 1869 and 1917, thirty non-commercial shallow wells were drilled in the area (Meyerhoff, 1980). Four classifications of wells (new-field wildcats, exploratory, outpost and development) account for 98% of the 3,878 additional wells drilled in the province through 1995 (Petroconsultants, 1996). The remaining 2% include service wells, water wells and "stratigraphic" tests. The first commercial oil field (Chib’yu) was discovered in 1930 and the first commercial gas field (Sed’yol) in 1935.