The characterization of reservoir rock, using Computer Assisted Tomography (CAT) with x-rays has been an objective of increasing popularity in the petroleum industry. In the present study, a medical x-ray CAT scanner was used for the study of core material from the "BIT member of the Clearwater Formation of the Lower Cretaceous Mannville Group in the Cold Lake area. Two pieces of core, each approximately 0.3 m long, were scanned at 0.01m intervals at a resolution of 0.00075m × 0.00075m × 0.005m. The raw CAT scan data were analysed using a postprocessing computer package developed in our laboratories at NOVA Husky Research. This analysis gives a detailed picture of the various heterogeneities within each core section including cracks, shale barriers and clay clasts, and also allows determination of core properties such as bulk density and porosity. Bulk densities determined from the CAT scan data are in good agreement with direct measurements obtained from several plugs taken from the core. The CAT scanning of the core successfully identified the locations for good plug selection. In addition, various types of heterogeneities were mapped in three dimensions. Significant core damage was observed which is atcributed to the coring and freezing processes. This paper presents the methodology of the scanning and the subsequent data analysis.
Computer Assisted Tomography (CAT) x-ray scanners have become a useful tool for the petroleum scientist and engineer. A detailed literature survey has recently been prepared by Kantzas (1989) while various applications are described in a variety of papers (e.g. Wellington and Vinegar (1987), Kantzas et.al (1989). of particular relevance to this work are various papers describing applications to heavy oil recovery (Fransham and Jelen (1986), Sedgwick and Miles-Dixon (1987) J Cuthiell and Sedgwick (1988). The quantitative representation of core properties has been the focus of a lot of our work recently. The effort focused on consolidated media and particularly in the Alberta dolomitic reservoirs. In this paper we address the potential of using the same technique for unconsolidated media. The CAT scanner can measure bulk density and effective atomic number directly by doing the so-called dual scanning i. e. one scan at an energy which is predominantly producing Compton scattering phenomena and one energy where photoelectric absorption is dominant. Fluid saturations can be measured in a core if the core is scanned while saturated and While dry at different energy levels and, if the fluids are scanned separately (Kantzas, 1988). This is very important when flow processes are monitored (e.g. Fransham and Jelen (1986), Cuthiell and Sedgwick (1988), Wellington and Vinegar (1987), Kanezas (1988)).
In the. case of heavy oil unconsolidated sands, the core is drilled and frozen immediately in an effort to preserye it at conditions as close to the reservoir as possible. When the core reaches the core lab, plugs are taken at different intervals and core analysis is commencing.
The recovery of unconsolidated sand during coring involves using a rubber or plastic sleeve core barrel.