Permeability From Production Logs - Method and Application To Tengiz Field

Michael Sullivan, Dave Belanger, Mark Skalinski, Steve Jenkins, and Peter Dunn
TengizChevroil, Atyrau, Kazakhstan

Estimation of effective permeability at the reservoir scale has been a long standing challenge in carbonate fields. Carbonate depositional and diagenetic history is often complex. This complex history can create a permeability field which is difficult to characterize in reservoir models. Permeability in vuggy or fractured intervals can be dramatically different from the matrix permeability measured in core plugs. However realistic estimates of oil recovery, and optimized reservoir management requires good estimates of the reservoir permeability.
In the Tengiz field, a giant carbonate reservoir in western Kazakhstan, a method has recently been developed to calculate apparent permeability (APERM) based on flow rate from production (PLT) logs. Incorporation of this flow calibrated apparent permeability into the static geologic earth model offers an elegant solution to the long-standing problem of how to best incorporate dynamic PLT data into a reservoir model.
A reservoir model recently built using APERM resulted in a step change improvement over previous methods where only static log based permeability transforms were used to populate the earth model. History match show that use of APERM has increased confidence in the permeability field. Permeability-Height (KH) estimates from the model are a much better match to well test KH, than models derived from core transforms. The models also have significantly more heterogeneity. Pulse tests show that this model has a better prediction of the inter-well connectivity. Models with the APERM data have provided higher confidence estimates of the future movement of gas injection in the Tengiz platform.

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