Abstract: Geochemical Maturation Modeling and Petroleum Systems, Offshore Azerbaijan, South Caspian Sea

SCHOELLKOPF, NOELLE B., JEREMY E. DAHL, and JANET B. MURPHY

Basin modeling studies, combined with biomarker and isotopic studies, suggest that there are at least two effective source sequences in the offshore South Caspian, namely the Oligocene to Lower Miocene Maykop Fm. and the Middle-to-Upper Miocene Diatom Suite.

Conventional kerogen kinetics, pyrolysis-GC and compositional kinetics of the Maykop Fm. were consistent with mixed Type III to Type II kerogen, with kinetic behavior intermediate between Types II and III.

1-D transient heat flow models, at wells and along a regional NW-SE depth-converted seismic section, were combined with depth-converted structural and isochore maps to produce regional maturity maps.

The South Caspian basin is unusually cool, with extreme subsidence and sedimentation rates and transient heat flow. Thus, the oil window is deep (top at 6-8 km below sea floor) and very broad (3.5-7 km). The transition to light oil, condensate and wet gas occurs at about 8-13 km and the conventional dry gas zone below 10-15 km.

The deepest burial and most mature source occurs in an arcuate trend, offshore of Bulla Deniz and Bakhar fields, extending south of Sabail-1. Here, both the Maykop and the Diatom Series have matured within the past 4-3 Ma. This very recent dual charge may explain why such vast oil reserves are present in coastal and offshore Azerbaijan. A shallower, linear depocenter extends parallel to, and south of, the Apsheron sill.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria