An Examination of the combustion and transport processes within fractured oil sands beds
Creators: name: Mehta, Sudarshan A., 1957-
Publisher: name: University of Calgary
Year: 1990

description: Bibliography: p. 306-316.
description: The main objectives of this study were twofold: First, to provide fundamental information on the processes of heating, low temperature oxidation (LTO), flammability, ignition, quenching, re-ignition, and diffusion controlled combustion in fractured beds of oil sands, associated with the in situ combustion process. Second, to provide a basic understanding of the volatilization, mass transfer, and ignition processes, related to in situ combustion, by macro-scale parametric studies involving high grade natural Athabasca oil sands. It is believed that this information would contribute towards a better perception of these processes in oil sands, and hence, towards the design and implementation of more successful and efficient in situ combustion projects for different reservoirs. Accordingly, an apparatus was developed to examine the processes of heating, low temperature oxidation (LTO), flammability, ignition, quenching, re-ignition, and diffusion controlled combustion within packed beds of oil sands with a central fracture. The beds were exposed to controlled, heated air/gas oxidizing streams and/or the combustion products of near lean limit mixtures of n-hexane and air. The effects of various physical parameters, such as the inlet stream temperature, core type and configuration, bitumen/oil saturation, stream flow rate, fracture type, etc., on these processes were investigated. A variety of cores were used, which included glass beads, clean Athabasca sand, synthetic cores containing different pure hydrocarbons and Athabasca sand, synthetic as well as natural Athabasca oil sands of different grades, and Pembina carbonate cores with two different oil saturations. Two different core configurations, viz. long, and segmented, were adopted. The fracture was simulated either by an open central circular channel or by the channel filled with 3 mm glass beads. The processes were simulated in over 250 runs using a variety of combinations of cores, core geometries, and operating conditions. In another experimental program, which employed three different modified experimental set ups, the volatilization, mass transfer, and ignition characteristics of spherical samples of high grade natural Athabasca oil sands were examined. The volatilization and mass transfer behavior in the samples during intermittent exposure to hot, low-velocity air streams were investigated. The ignition, quenching, and re-ignition of the samples, in the streams of combustion products of lean H 2 -air mixtures, were studied. A model was developed to determine the effective activation energies of the fresh, and the pre-oxidized samples. High pressure ignition behavior of fresh and pre-oxidized samples in oxygen and oxygen-diluent environments were established. The effects of pressure and the strength of the ignition source on the ignition behavior of the samples were also studied. Preand post-run morphology of the samples from all the experiments was examined. A total of over 3500 tests were carried out. In addition, the thermal conductivity of various granular materials, including clean Athabasca sand, over a temperature range of 25° to S00°C, was determined using a one-dimensional cylindrical cell system. These thermal conductivity values were required in order to examine the heating characteristics of the fractured beds.