4) Early Pliocene palynology of the South Caspian Basin, Azerbaijan

STEPHEN LOWE (1) and KEITH RICHARDS (2)
(1) BP Exploration,  Sunbury on Thames, UK
(2) KrA Stratigraphic, Deganwy, UK

POSTER ABSTRACT: Presented at American Association of Stratigraphic Palynologists, Annual General Meeting, San Antonio, Texas, USA (November 2001). **WINNER: AASP Best Poster Award (2001)**

PALYNOSTRATIGRAPHY OF EARLY PLIOCENE PETROLEUM RESERVOIRS IN THE SOUTH CASPIAN BASIN – EXAMPLES FROM THE ACG (AZERI-CHIRAG-GUNASHLI) FIELD, OFFSHORE AZERBAIJAN

High resolution palynological studies increasingly play an important role in the geological description and modelling of  petroleum reservoirs. This is particularly true in the Early Pliocene, Lower Productive Series (Pereriv & Balakhany X reservoirs) of the South Caspian Basin, where the abundance and high diversity of palynomorph assemblages enables particularly detailed stratigraphic sub-division, intra-reservoir correlation and facies description. The results and interpretations of fully quantitative palynological analyses of cored Pereriv and Balakhany X reservoirs in the ACG field, offshore Azerbaijan are presented. A palynofacies model is outlined which enables the recognition of palynomorph and sediment provenance, environments of deposition and climatic fluctuations. This model indicates that the primary reservoirs were deposited in an extensive lacustrine delta system, analogous to the modern Volga delta, whilst inter-bedded mudstones are predominantly characterised by relatively arid palynofloras deposited in lake settings starved of coarse clastic input. Climatic fluctuations are recognised palynologically at a range of frequencies and are believed to have exerted a major influence on the nature and volume of sediment supply as well as changes in relative lake levels.

The reservoir description of the ACG field has also been significantly enhanced by the palynological characterisation of individual intra-reservoir mudstone units. Hence the specific, distinctive and sometimes unique palynological assemblage characteristics of a particular mudstone, enable us to differentiate between mudstones of limited local extent from those of field-wide lateral extent (important factors for modelling the barriers and baffles to hydrocarbon flow).

This work on the ACG field is ongoing and is part of a multi-disciplinary effort using seismic character, sedimentological core description and petrophysical data to provide realistic parameters for dynamic simulation in sector and full field models. Having established a robust intra-reservoir biozonation the next phase will involve its application in "real time" to assist wellsite operational decision making.

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