Measurement of Pore Architecture of Carbonate Reservoirs Using Computed Tomography

ABSTRACT

Carbonate reservoirs contain over 50% of the world hydrocarbons. The processes of precipitation, lithofication and diagenesis, and particularly dissolution phenomena in carbonate reservoirs, create complicated pore architectures. This complexity is partially resolved using computerized tomography (CT Scanning). Understanding of variation of pore architecture can help to analyze core analysis derived rock properties such as porosity, permeability and connectivity.

In carbonate reservoirs pore architecture can be controlled by salinity, temperature, pH and the amount of calcium carbonate of water. New research has documented the role of dissolution in carbonate rocks through lithofication to provide various ranges of pore architecture. The different fluid pH levels in the reservoir rocks yield a range of dissolution scenarios. Hence carbonate formations generally have complex pore architectures. Moreover, in comparison to siliciclastic sandstones, there are not enough works on pore architecture published in the literature.

Core analysis is applied as a tool to measure the pore architecture and finally characterize the reservoir. Core samples from the AB-Teymur oil field were prepared. Pore architecture and pore classes are the important key in understanding the heterogeneous and complicated AB-Teymur carbonate oil reservoir. Consequently, complicated pore architecture in carbonate rocks influences the pore classes, and also determines the morphology of vuggy, moldic, channel, cavernous and fracture porosity.

Measurements of pore architecture are obtained by conducting different runs on various core samples and the prediction of pore architecture clarifies the problems which are regularly a critical control on reservoir quality. A better explanation of pore architecture is obtained by using X-ray CT scanning in core plugs of a carbonate reservoir. The results of this study can be used to improve production and recovery of oil and gas in carbonate reservoirs.

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