Plate Tectonic Controls on Play Element Distribution in the North Caspian Basin, Kazakhstan

B. A. Rassmann, I. O. Norton, A. A. Kaplan

Several world-class fields have been discovered in the pre-salt Paleozoic rocks of the North Caspian Basin. Timing of plate motion, pre-existing 'basement' type and grain, and worldwide eustatic events combine to set up these extraordinary fields.

Astrakhan and Tengiz Fields characterize conditions on the south side of the North Caspian Basin and Karachaganak Field epitomizes conditions on the north-east side of the basin. Control on reservoir distribution in these fields is thought to be a product of several factors 1) an 'ultimate substrate' of continental block which is riding high in Late Middle to Early Upper Devonian time, 2) the localization of Devonian stromatoporoid buildups on these high blocks, and 3) accommodation rates that allow for aggradational stacking patterns of carbonates through the Middle Carboniferous.

Controls on source rock distribution in the North Caspian Basin may be 1) the initial Proterozoic to Early Paleozoic bathymetric profile which persists through the Paleozoic due to reactivation on the northern margin and 2) intermittent paleo-oceanographic restrictions imposed by arriving Devo-Carboniferous island arcs and Scythia/Turan and Ust Urt blocks.

Finally, excellent restricted and evaporitic seals are deposited as a function of the final and complete isolation of the Uralian seaway during major plate collision of Russian Platform with the Siberia/Kazakhstan block and the worldwide Late Permian/Triassic sea level fall.

This perfect interplay of tectonics, eustacy, and 'basement' type and grain went a long way to setting up the remarkable hydrocarbon system in the North Caspian Basin of Kazakhstan.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995