In situ recovery processes being developed for extraction of heavy hydrocarbon resources form Alberta's oil sand deposits involve heating by massive steam injection or in situ combustion. Proposed in situ extraction schemes present a number of difficult geotechnical engineering problems related to safe, economic design of extraction facilities and resource management in a high temperature/high pressure subsurface environment. A laboratory testing facility has been developed to study behaviour of undisturbed oil sand at temperatures to 300°C (600°F) and pressures to 30 MPa (4500 psi). The facility includes both triaxial and one-dimensional (consolidometer) compression test cells. Facilities and procedures for undisturbed sampling, sample preparation and testing of this unique material are described. Permeability, thermal expansion and compression, shear strength and deformation properties, and pore pressure response to undrained heating of undisturbed oil sand samples have been measured at elevated temperatures and pressures.
INTRODUCTION
Oil sands are an important world energy resource by virtue of the magnitude of known reserves. Estimated in-place volumes of heavy hydrocarbons in oil sand deposits throughout the world approach 3000 billion barrels which is nearly equivalent to the total discovered conventional medium and light gravity oil reserves in-place in the world. More than 90 percent of known heavy hydrocarbon reserves occur in oil sand deposits located in Alberta, Western Canada and in the Orinoco Heavy Oil Belt of Eastern Venezuela (Demaison, 1977). Although abundant, the extremely high viscosity of the crude bitumen in oil sands makes conventional recovery by pumping impractical. Approximately 4 percent of Alberta oil sand reserves are buried at depths less than 50 m and are economically recoverable by surface mining techniques (Alberta Energy and Natural Resources, 1979). In situ extraction procedures have had to be developed for the remaining 96 percent of reserves buried at greater depths. In situ extraction methods generally involve heating the oil sand with pressurized steam or by in situ combustion. Both techniques are under active investigation at the pilot project stag. A hybrid method, Mine Assisted In Situ Processing (MAISP) is also under study. MAISP involves the development of an underground mine system of vertical shafts and tunnels in or adjacent to the oil sand in order to provide access for horizontal steam injection and production wells (Devenny and Raisbeck, 1980). This layout is intended to provide a more cost-effective production facility through reduced heat losses and a higher density of wells within the formation. The concept has already been adopted in the USSR to recover heavy oil in north-eastern Siberia near Yarega. Figure 1 illustrates in a general manner some of the extraction processes. In situ extraction from oil sands presents a number of difficult geotechnical problems because of the peculiar properties of the oil sands, (Dusseault and Morgenstern, 1978), the scale of the recovery schemes and the elevated pressure-temperature environment resulting from massive steam injection and/or combustion. For example, and understanding of the mechanics of fluid injection processes requires knowledge of how heated fluid-filled fractures propagate in a deformable cohensionless medium. In situ stresses may be altered locally by heating and/or pressurization.
