The South Chukchi Sedimentary Basin: Structural Pattern and Hydrocarbon Potential (Chukchi Sea, Russian Arctic)

Vladimir Verzhbitsky¹, Erling Frantzen², Kjell Trommestad², Tatyana Savostina¹, Alice Little³, Magnar Ullnaess², Sergey Sokolov⁴, Marianna Tuchkova⁴, Tom Travis⁵, and Oksana Martyntsiva^5
1TGS-NOPEC Geophysical Company Moscow, Moscow, Russian Federation
²TGS-NOPEC Geophysical Company ASA, Asker, Norway
³TGS Geological Products and Services, Stavanger, Norway
⁴Geological Institute, Russian Academy of Sciences, Moscow, Russian Federation
⁵TGS-NOPEC Geophysical Company (UK) Limited, Bedford, United Kingdom

The South Chukchi sedimentary rifted basin (SCB) separates the Late Kimmerian Chukotka Fold Belt and the Wrangel Arch, and represents the NW continuation of well-known Hope Basin of the Chukchi Sea (US sector), filled by Cenozoic nonmarine, marine and lacustrine rocks [Tolson, 1987]. During the summer 2006 TGS-NOPEC conjointly with “Geophysical Solutions Integrator” acquired new seismic data in the Russian part of the Chukchi Sea. The main stages of SCB development are comparable with those of the Hope basin [Tolson, 1987; Elswick, Toro, 2003]. The analysis of onshore data from Chukotka and Wrangel Island [Natal’in, 1999; Kos’ko et al., 1993] points to the beginning of rift-related sedimentation from Late Cretaceous-Paleocene time. In the SCB the sediment thickness above acoustic basement seldom exceeds 3-4 km, but can locally reach 5-6 km. The geometry of the faults indicates an extensional/transtensional setting of the SCB evolution, although compressional structures (folds and reverse faults) also occur. The low-angle pre-rift thrust faults are recognized at the base of the SCB. Most probably, they represent the highly deformed Triassic sequences overthrusting the much less deformed Upper Jurassic-Lower Cretaceous strata, as shown earlier for Central Northern Chukotka [Baranov, 1995]. The changes in seismic phase or polarity and areas of anomalous reflectivity in the upper sediments may point to a gas presence. These phenomena are often associated with listric fault planes that penetrate the pre-rift sequences and acoustic basement. The syn-orogenic (pre-rift) Upper Jurassic-Lower Cretaceous organic-rich terrigenous sequence may constitute a major gas source rock. The analysis of bottom sediments in this area has revealed anomalous concentrations of migrated hydrocarbon gases, suggesting significant HC prospectivity of the South Chukchi basin [Yashin, Kim, 2007].

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