Abstract: The Origin of Oil and Gas Accumulations in the Western Sector of the South Caspian Sea

Akif A. Narimanov, Michael A. Abrams, John F. Ruehlman

The western sector of the South Caspian Sea is the most studied offshore area within the intermontane South Caspian Depression. The base of the sedimentary section occurs at depths of 15-18 km and the thickness of Pliocene-Quaternary section reaches 10 km. Hundreds of drill wells, some exceeding 6 km, have been drilled in the study area and adjacent onshore providing detailed subsurface information for evaluating the petroleum system.

Molecular characterization of Miocene-Pliocene reservoired hydrocarbons indicate most of the oils have been sourced from the same or similar source facies at temperatures near or less than peak generation. Examination of Neogene and Paleocene source rock organic richness and molecular character indicates the hydrocarbons are not syngenetic in origin but most likely sourced from Lower Miocene or older shales. Maturation modeling based on well and seismic data indicates temperatures sufficient to generate large volumes of hydrocarbons does occur at depths from 6.5 to 12 km, 2 to 3 times greater than their present reservoir depths. A multi-stage model of hydrocarbon emplacement for evolving structural and stratigraphic traps has been postulated based on the distribution and type of hydro arbons, tectonic-stratigraphic development, hydrocarbon generation models, and probable migration pathways.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France