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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Evaluating the Petrophysical Parameters of Carbonate Reservoirs, Offshore Abu Dhabi, Using Conventional Core Analysis from Different Scales of Core Samples

Khalil I. Hosani1; Christoph T. Lehmann1; Mohamed Sayed Ibrahem1; Mohamed Ridha Ouezzani1

(1) FDD (UDS), ADMA-OPCO, Abu Dhabi, United Arab Emirates.

A detailed Conventional Core Analysis (CCA) was performed on Jurassic carbonate reservoir samples from a new field offshore Abu Dhabi. The conventional core analysis study included porosity and permeability measurements on plugs samples, MICP, core description, and a reservoir characterization study. Different type of conventional core data were collected, evaluated and incorporated in this study. The study was performed in order to define depositional environment, facies, and the distribution of reservoir rock types. This data was then used to define the flow units which are the building block for a 3D geological model.

Limestone reservoir samples are highly complex and reservoir quality is controlled by the presence of mud and the amount of diagenesis. In addition, dissolution of semi-stable biogenic components, such as stromatoporoids, is creating vuggy porosity. This raises the question: Does a plug sample of the reservoir reflect the petrophysical characteristics of the reservoir and its flow performance?

The CCA study was performed on 1.5 inch plugs (historic data) and 2.5 inch plugs (more recent data). Sampling often avoids vuggy, fractured and highly cemented areas of the core. The studied field is faulted and reservoir quality might be affected by late stage diagenesis. In addition, certain reservoir facies, such as stromatoporoid build-ups exhibit large-scale vuggy porosity. So, plugs are often not the best sampling technique to represent the reservoir in order to determine petrophysical characteristics and ultimately the flow performance.

Whole core samples which are representing different lithofacies types were selected from 2 wells to measure porosity & permeability and conduct CT scans. The whole core data will be used to generate a relationship with plug-size data to allow upscaling the permeability to be consistent with the dynamic well flow test data while maintaining the vertical contrast of permeability, which crucial in characterizing the flow dynamics of stratified reservoir.

Comparing the petrophysical parameters using different scales of reservoir samples (plugs versus whole core) might help to addressing the role of large scale features such as fractures and diagenesis (vugs and its connectivity) on reservoir performance and reduce, therefore, the petrophysical uncertainty in the reservoir models.