Mathematical Modeling of Steam Assisted Gravity Drainage
- Serhat Akin (Middle East Tech U.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- October 2005
- Document Type
- Journal Paper
- 372 - 376
- 2005. Society of Petroleum Engineers
- 5.4.10 Microbial Methods, 5.3.9 Steam Assisted Gravity Drainage, 4.6 Natural Gas, 4.3.3 Aspaltenes, 4.1.5 Processing Equipment, 5.4.2 Gas Injection Methods, 4.1.2 Separation and Treating, 5.8.5 Oil Sand, Oil Shale, Bitumen, 5.4.6 Thermal Methods, 1.8 Formation Damage, 5.2.1 Phase Behavior and PVT Measurements
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A mathematical model for gravity drainage in heavy-oil reservoirs and tarsands during steam injection in linear geometry is proposed. The mathematicalmodel is based on the experimental observations that the steam-zone shape is aninverted triangle with the vertex fixed at the bottom production well. Bothtemperature and asphaltene content dependence on the viscosity of the drainedheavy oil are considered. The developed model has been validated withexperimental data presented in the literature. The heavy-oil production rateconforms well to previously published data covering a wide range of heavy oilsand sands for gravity drainage.
Gravity drainage of heavy oils is of considerable interest to the oilindustry. Because heavy oils are very viscous and, thus, almost immobile, arecovery mechanism is required that lowers the viscosity of the material to thepoint at which it can flow easily to a production well. Conventional thermalprocesses, such as cyclic steam injection and steam-assisted gravity drainage(SAGD), are based on thermal viscosity reduction. Cyclic steam injectionincorporates a drive enhancement from thermal expansion. On the other hand,SAGD is based on horizontal wells and maximizing the use of gravity forces. Inthe ideal SAGD process, a growing steam chamber forms around the horizontalinjector, and steam flows continuously to the perimeter of the chamber, whereit condenses and heats the surrounding oil. Effective initial heating of thecold oil is important for the formation of the steam chamber ingravity-drainage processes. Heat is transferred by conduction, by convection,and by the latent heat of steam. The heated oil drains to a horizontalproduction well located at the base of the reservoir just below the injectionwell.
Based on the aforementioned concepts, Butler et al. derived Eq. 1 assumingthat the steam pressure is constant in the steam chamber, that only steam flowsin the steam chamber, that oil saturation is residual, and that heat transferahead of the steam chamber to cold oil is only by conduction. One physicalanalogy of this process is that of a reservoir in which an electric heatingelement is placed horizontally above a parallel horizontal producing well.
|File Size||208 KB||Number of Pages||5|
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