Petrophysical Characterization of a Lower Cretaceous Carbonate Reservoir Onshore Abu Dhabi, UAE

Suryanarayana Karri¹ and Yousef Al Mehairi^2
1Sproule International Limited, Calgary, AB, Canada
²Abu Dhabi Company for Onshore Oil Operations, Abu Dhabi, United Arab Emirates

A giant oil field onshore Abu Dhabi is a significant hydrocarbon producer from a Lower cretaceous carbonate formation. Recently, sequence stratigraphic framework was defined using extensive analysis of available core data and well log correlations. In addition, the study identified seven reservoir and three non-reservoir lithofacies and ten reservoir rock types. However, since the sequence stratigraphic study relied on core data it could not address the issue of prediction of lithofacies and reservoir rock types in un-cored intervals.

Construction of a 3D-Geological model for the reservoir required the population of the grid cells with petrophysical properties such as porosity, permeability and water saturation for a meaningful upscaled model for reservoir simulation. For the geological and the petrophysical models to be in consonance, it is imperative that both should honor the sequence stratigraphic framework. With this basic premise, a petrophysical model was constructed in parallel to the 3D geological model with an emphasis on estimation of reservoir rock types and water saturation for a better control on the distribution of these parameters in the geological model.

The reservoir rock types were generated using lithofacies and flow zone indicator as the key parameters. The statistics show that the log derived reservoir rock types are comparable to the core-defined reservoir rock types. Then, for each reservoir rock type capillary pressure curves, saturation height functions, Leverette-J functions from both core and log data were generated and were compared with the log derived water saturation. It is shown that the log derived saturation height functions replicated the water saturation profile better than the rest of the methods. Examples are shown to demonstrate that the petrophysical model is realistic by honoring the sequence stratigraphic framework.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas