Petroleum Systems of Sedimentary Basins in the Chukchi Sea

Elena V. Gretskaya, Irina Rybak-Franko, and Alexander V. Savitsky
Interpretation group, DMNG JSC, Yuzhno-Sakhalinsk, Russia.

Study objective. The objective of the study is to describe petroleum systems of the Long Chukchi and North Chukchi sedimentary basins in the Chukchi Sea. The petroleum system includes all the elements necessary for initiation and existence of hydrocarbon (HC) accumulations: source rocks, reservoirs and seals, and reflects temporal and spatial coincidence of HC generation, migration and accumulation in traps. The recognised petroleum system in the basins provides the basis for evaluation of the forecast HC resources.

Study methods. 1. Seismic-stratigraphic and seismic-facies analysis. 2. Basin modeling with reconstruction of the thermal history of the basin, evaluation of the realization degree of the initial HC potential of the rocks, construction of a model of migration and HC saturation of the rocks.

Study results. Two large sedimentary basins (North Chukchi and Long Chukchi) are recognised from the integrated geological-geophysical data interpretation (Petrovskaya et al., 2008) for the Chukchi Sea shelf. Maximum thickness of the sedimentary section with a wide stratigraphic range of deposits is about 16 km in the North Chukchi basin. Two potential petroleum systems are recognised in the North Chukchi basin from the basin modeling results: Ellesmerian and Lower Brookian, which are of regional extent and correspond to the basin systems of the continental slope of Northern Alaska (Sherwood, 1998). Oil source rocks of the Ellesmerian system in the deepest parts of the basin started to generate HC in Late Jurassic. Source rocks of the Lower Brookian system started generation in Early Eocene. Oil source deposits have realized their initial HC potential to different degrees by the present time. The predicted HC accumulations are confined to sand reservoirs of different age. Structural and structural-stratigraphic traps are formed by tectonic activity in Late Jurassic - Early Cretaceous and Late Cretaceous - Cenozoic. A petroleum system related to the Rift Complex occurs in the area of maximum subsidence in the Long Chukchi Basin.

Conclusion. Large volume and regional extent of the Ellesmerian and Lower Brookian petroleum system rocks suggest that the HC potential of the North Chukchi sedimentary basin is high. Modeling results confirm that HC pools can be formed in the sedimentary basins of the Chukchi Sea.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia