Oil and Gas Potential of the West Kamchatka Trough

Abstract

The west Kamchatka trough (WKT) is a region with a two-stage structural pattern (i.e., Cenozoic cover and pre-Cenozoic basement). The composition of hydrocarbons in local accumulations in the trough, and the present-day and paleotemperature distributions suggest that the hydrocarbons have a complex history. The WKT basement complexes, which have been penetrated by wells, are exposed in uplifts in the southern Median-Kamchatka ridge (MKR), where it is possible to study their composition and structure. The nappe structure of the MKR comprises various sedimentary and volcanoclastic complexes, including some highly carbonaceous Mesozoic clastics. Geodynamic analysis of the MKR rocks shows that during the Mesozoic, two separate island-arc terrances evolved in this part of the northwest Pacific, behind which a back-arc basin developed. In the Paleogene, rocks of this basin were overridden by nappes and metamorphosed. New understanding of the structure and evolution of the older complexes suggest that hydrocarbon accumulations may exist in underthrust zones in the WKT basement, which contains both reservoirs and source rocks. Subsequent evolution of the region was accompanied by the formation of zones of anomalously high formation pressure. Hydrocarbons drained upwards along faults and accumulated in structures in the cover, in places reaching the surface. Existing drillingmore » and seismic data do not help with the interpretation of the basement structure because these operations were aimed at discovering local structural traps in the Cenozoic cover. Future oil exploration surveys in the region will require remote sensing methods that have much deeper penetration.« less