Cavitating flows entail phase change and hence very large and steep density variations in the low pressure regions. These are also very sensitive to: (a) the formation and transport of vapor bubbles, (b) the turbulent fluctuations of pressure and velocity, and (c) the magnitude of noncondensible gases, which are dissolved or ingested in the operating liquid. The presented cavitation model accounts for all these first-order effects, and thus is named as the “full cavitation model.” The phase-change rate expressions are derived from a reduced form of Rayleigh-Plesset equation for bubble dynamics. These rates depend upon local flow conditions (pressure, velocities, turbulence) as well as fluid properties (saturation pressure, densities, and surface tension). The rate expressions employ two empirical constants, which have been calibrated with experimental data covering a very wide range of flow conditions, and do not require adjustments for different problems. The model has been implemented in an advanced, commercial, general-purpose CFD code, CFD-ACE+. Final validation results are presented for flows over hydrofoils, submerged cylindrical bodies, and sharp-edged orifices. Suggestions for possible extensions of the model implementation, e.g., to nonisothermal flows, for ingestion and mixing of noncondensible gases, and for predictions of noise and surface damage are outlined.

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In an environment of low oil prices and low economic returns for heavy oil operations, SAGD and VAPEX processes appear very promising from a technical point of view. The purpose of this paper is to present guidelines for screening heavy oil reservoirs for exploitation by Steam Assisted Gravity Drainage (SAGD) and VAPEX processes. Viability in the field would be strongly governed by factors such as net pay thickness, oil viscosity, presence of gas cap or bottom water, barriers to vertical flow, containment of the steam or vapour chamber within the target area, lateral and vertical extent of steam/vapour chambers, number of new horizontal/vertical wells to be drilled, solvent recovery, facilities requirements, etc. Exploitation viability of heavy oil reservoirs is evaluated under different reservoir settings using a combination of reservoir/geological analyses and numerical simulation. This evaluation helps provide guidelines for screening reservoir prospects for the application of SAGD/VAPEX processes. The viability of these processes is sensitive to the reservoir characteristics of the specific target areas. Introduction The exploitation of heavy oil and bitumen is of primary interest to many oil companies due to the decline of conventional oil reserves. The magnitude of these resources worldwide, is of the order of 1 trillion m3 (6 trillion bbl) of oil in place, a major part of which is present in Venezuela. Canada is ranked second with an estimated original oil in place (OOIP) of 400 billion m3 (2.7 trillion bbl); twice that of the total conventional oil deposits in the Middle East (Janisch, 1979). The heavy oil and oil sand deposits of the USA are approximately 16 and 10 billion m3 of in-place resource respectively, mostly in Utah, Texas, Kentucky and California. The province of Alberta contains significant heavy oil and oil sand deposits, the total estimated resource being about 250 billion m3, buried at a depth of 0–800 m, of which only less than 5% is suitable for open-pit mining from shallow reservoirs (Wightman, 1989). The heavy oil deposits of Alberta and Saskatchewan consist of Athabasca (McMurray Formation), Wabasca (Grand Rapids Formation), Cold Lake (Clearwater Formation), Peace River (Blue Sky/Gething Formation), Lloydminster (Mannville Formation) and Grosmont Formation deposits (Figure 1). These collectively represent fluvial, deltaic, and marine depositional environments. The oil bearing deposits may often be composed of numerous stacked sandstone bodies which may or may not be in communication with one another. Vertical and lateral barriers to flow may consist of extensive shale layers, or localized shale lenses and shale filled channels. Other features which may affect the pay zone continuity include erosional features, salt collapse sink holes and fractures. The most critical factor to SAGD and VAPEX would be the ability of the steam/vapour chamber to confine the injected fluids, thus facilitating the recovery of mobilized bitumen/solvent. Therefore, in addition to pay zone continuity, other features such as grain size variation within the pay zone and the localized size, shape, and structure of the pay zone may promote or discourage such confinement and recovery of the injectant. The response to SAGD/VAPEX is therefore likely to be very site-specific. Earlier studies (Kasraie et al., 1996) had suggested limitations of 10 metres of continuous pay and a minimum permeability of 100 md for these processes to be economically viable, assuming confinement and injectant recovery. Such screening criteria (based on net pay and permeability) would be significantly affected by localized reservoir features which are controlled by the depositional environment and post depositional alterations (diagenesis). P. 867