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

A detailed Conventional Core Analysis (CCA) was performed on Jurassic carbonate reservoir samples<br>from a new field offshore Abu Dhabi. The conventional core analysis study included porosity and<br>permeability measurements on plugs samples, MICP, core description, and a reservoir characterization<br>study. Different type of conventional core data were collected, evaluated and incorporated in this<br>study. The study was performed in order to define depositional environment, facies, and the<br>distribution of reservoir rock types. This data was then used to define the flow units which are the<br>building block for a 3D geological model.<br>Limestone reservoir samples are highly complex and reservoir quality is controlled by the presence of<br>mud and the amount of diagenesis. In addition, dissolution of semi-stable biogenic components, such<br>as stromatoporoids, is creating vuggy porosity. This raises the question: Does a plug sample of the<br>reservoir reflect the petrophysical characteristics of the reservoir and its flow performance?<br>The CCA study was performed on 1.5 inch plugs (historic data) and 2.5 inch plugs (more recent data).<br>Sampling often avoids vuggy, fractured and highly cemented areas of the core. The studied field is<br>faulted and reservoir quality might be affected by late stage diagenesis. In addition, certain reservoir<br>facies, such as stromatoporoid build-ups exhibit large-scale vuggy porosity. So, plugs are often not the<br>best sampling technique to represent the reservoir in order to determine petrophysical characteristics<br>and ultimately the flow performance.<br>Whole core samples which are representing different lithofacies types were selected from 2 wells to<br>measure porosity & permeability and conduct CT scans. The whole core data will be used to generate a<br>relationship with plug-size data to allow upscaling the permeability to be consistent with the dynamic<br>well flow test data while maintaining the vertical contrast of permeability, which crucial in<br>characterizing the flow dynamics of stratified reservoir.<br>Comparing the petrophysical parameters using different scales of reservoir samples (plugs versus<br>whole core) might help to addressing the role of large scale features such as fractures and diagenesis<br>(vugs and its connectivity) on reservoir performance and reduce, therefore, the petrophysical<br>uncertainty in the reservoir models.