ABSTRACT: Oil and Gas Basins of the Pacific Margin of the Soviet Union: Proven and Probable

V. E. Khain, Yu. K. Burlin

The Pacific margin of the Soviet Union comprises a large number of sedimentary basins, many of rather small size, but some more extensive, of which five contain already proven hydrocarbon reserves: Sakhalin, Tartar Strait, West Kamchatka, Khatyrka, and Anadyr. The intensely folded and partly metamorphosed basement of the sedimentary basins of the region consists of Paleozoic and Mesozoic rocks, accreted in the Late Mesozoic and Paleogene to the ancient, Precambrian continental blocks of Arctica (Hyerborea), Siberia, Bureya-Khanka continents and comprising Okhotsk and Central Kamchatka microcontinents. The sedimentary infill of the basin is represented mainly by terrigeneous and siliceous deposits of Late Cretaceous and, principally, of Cenozoic age, with some addition of olcaniclastic material. The thickness of sediments attains many thousands meters.

By their geodynamic nature, the sedimentary basins of the Pacific margin of the Soviet Union belong to different types of basins recognized in active margin environment. Some are of the fore-arc type, among them Navarin, Khatyrka, and North and East Sakhalin; others are of the back-arc type: West Kamchatka, Tartar Strait, and others. In the rear part of the margin we recognize the northern continuation of a huge continental rift system, which includes the North China Bohai Bay and Sunliao basins. In the Soviet Union, this system comprises the Zeya-Bureya, Middle Amur, North Okhotsk, Markovo, and Anadyr basins. The basal strata of the basin's sedimentary infill, as a rule, gets younger from the mainland to the ocean.

These sedimentary basins were subjected to rather moderate folding and high-angle faulting, which occurred mainly in the Pliocene and even the Pleistocene, and involved all the sequence of the basin infill. The traps are mostly structural, anticlinal or fault bounded. Reservoir rocks are represented by sandstones or fractured siliceous shales. Seals are represented by argillaceous rocks. Source rocks could be considered pelitic strata of Cretaceous and Paleogene age and Oligocene-Miocene diatomaceous shales.

Among the yet unexplored or insufficiently explored basins of the region, most promising are North Okhotsk, Olyntorsky, and Navarin basins. Most of the other basins have insufficient thickness of sediments and/or lack of good seals or source rocks.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990