Pereriv Formation Heterogeneity and Connectivity: Insights from the Azeri Field during Production

Hamlet Ibrahimov¹, Richard Jolly², and Ivan Pinzon^3
1BP/AzSPU company, Baku, Azerbaijan
²BP/Sunbury, London, United Kingdom
³BP/AzSPU, Baku, Azerbaijan

The Azeri-Chirag-Gunnashli (ACG) field is located on the eastern end of an anticline feature known as the Apsheron Trend. Regionally there are 16 hydrocarbon-bearing reservoir sandstones of Pliocene age, nine of which form part of the ACG development. They comprise stacked fluvio-deltaic sandstones deposited by the giant Paleo-Volga delta, which flowed from north to south into the lacustrine South Caspian Basin.
These productive reservoirs are stratigraphically divided into the Balakhany and Pereriv formations, these are further subdivided into nine individual reservoirs. The four major reservoirs all show high porosities and permeabilities, with typical values in the ranges 20-25% and 100-1000 mD respectively.
A challenged faced during the development of ACG is determining the impact of depositional heterogeneity on the dynamic performance of the reservoir. The development requires a comprehensive understanding of the contributions of each reservoir to maintain offtake and effective sweep.
Examination of pressure breaks often highlight pressure differentials across observable shales, pre-production from Azeri. However during production shows that the number of pressure breaks in the stratigraphy increases, and that pressure depletion is not always even. This suggests that the intra-reservoir shales are of significant extent to impact depletion. To aid in understanding these further Distributed Temperature Sensing (DTS) provides a realtime and continuous monitoring of flow into a well, and consequently can be used to identify heterogeneities in that flow. At a gross level the information derived is in agreement with expected rate profiles as derived from rock properties calculated from cores and logs.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece