Abstract
Heat and fluid flow at the edge of steam chambers found in thermal recovery processes such as steam-assisted gravity drainage and cyclic steam stimulation remain unresolved. Given the multiple phases present and contrast of thermophysical properties, it remains unclear where instabilities occur within this thin, yet critical, zone of the process. In the research reported here, heat and fluid flow are examined in vertical and horizontal sections of a steam chamber to understand the differences between the two orientations by using detailed and fine-gridded thermal reservoir simulation models. The results show that heat transfer in vertical and horizontal directions are different with greater heat transfer found in the vertical orientation. In the vertical direction, heat transfer occurs with mobilized bitumen draining with subsequent steam moving into the emptied pore space. Conduction beyond the edge of the chamber dominates and heated, low viscosity bitumen fingers into cold, higher viscosity bitumen at the edge of the chamber. Relative permeability effects are observed which can interfere with enhanced oil mobility.
Highlights
IntroductionCyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) are examples of commonly used thermal enhanced oil recovery methods for recovering heavy oil and bitumen (HO/B)
Cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) are examples of commonly used thermal enhanced oil recovery methods for recovering heavy oil and bitumen (HO/B).These processes rely on the use of steam as an agent to transfer heat to the cold HO/B raising its temperature
Whereas it was originally believed that the linear instability that arises at the steam interface will result in non-uniform heating of the bitumen leading to poor sweep efficiency, Zhu et al [8] show that linear instability at the steam–oil interface is induced by ex-solution of solution gas from bitumen
Summary
Cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) are examples of commonly used thermal enhanced oil recovery methods for recovering heavy oil and bitumen (HO/B). The concept of displacement is not entirely fitting for thermal gravity drainage processes This is especially the case where the flows are counter-current—this is the case when bitumen is mobilized above a steam zone and drains downwards towards the base of the chamber. From a heat transfer point of view, the steam movement into the depleted bitumen space is by convection, prior to bitumen drainage, conduction of heat occurs a counter-current flow process—the bitumen drains downwards whereas the steam rises upwards. Recognising the impact of oil saturation and relative permeability on the mobility chamber in a SAGD process They accounted for the onset of condensate flow which induces heat of the displaced as heat is transferred, they derived a newwas theory towith predict the oilthermal drainage rate transfer byoil convection. It is believed that this enhances the heat transfer area resulting to additional heat transferred to the bitumen reservoir
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