A New Perspective on Tracking Energy Transfer in SAGD during Three-Dimensional Numerical Field-Scale Simulations
- Cosmas Chigozie Ezeuko (U Of Calgary) | Jing Yi Jacky Wang (University Of Calgary) | Arindom Sen (U. of Calgary) | Ian Donald Gates (U. of Calgary)
- Document ID
- Society of Petroleum Engineers
- SPE Heavy Oil Conference and Exhibition, 12-14 December, Kuwait City, Kuwait
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 5.3.9 Steam Assisted Gravity Drainage, 5.1.5 Geologic Modeling, 5.5.8 History Matching, 4.3.4 Scale, 2.3 Completion Monitoring Systems/Intelligent Wells, 5.1 Reservoir Characterisation, 5.8.5 Oil Sand, Oil Shale, Bitumen, 1.2.2 Geomechanics, 5.4.6 Thermal Methods, 4.6 Natural Gas, 2.4.3 Sand/Solids Control, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 1.2 Wellbore Design, 5.5 Reservoir Simulation, 5.1.1 Exploration, Development, Structural Geology, 5.5.3 Scaling Methods, 6.5.2 Water use, produced water discharge and disposal
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Numerical reservoir simulations have successfully been used for performance analysis of several commercial steam-assisted gravity drainage (SAGD) heavy oil recovery projects. The inherently complex calculations involving mass and energy balances, along with consideration for advanced geomechanics, culminate in a strong time limitation for field-scale simulations of SAGD processes. As a result, significantly homogeneous gridding has traditionally been used for downwell
directions, with grids sizes sometimes exceeding 100 m for three-dimensional simulations of SAGD. This represents a compromise which requires further quantitative analysis to clearly understand the implications on uniform steam chamber development and the accuracy of performance predictions. At this point, most simulations are not capable of predicting realistic field performance, especially in the downwell direction, of a given reservoir since grid resolution is poor. In this study, a full-field reservoir model representative of a McMurray reservoir is used to analyze the implications of longitudinal grid homogeneity on the propagation of a SAGD steam chamber. In addition, a novel use of flowing steam quality plots to visualize steam migrations and characterize heat transfer during SAGD is presented. The results illustrate the requirements on grid block dimensions necessary to resolve heterogeneities and accurately represent physical phenomena such as flow and heat transfer. The findings of this work provide useful guidelines and have implications for future design and performance analysis of SAGD projects using numerical reservoir simulations.
Heavy oil describes oil with API gravity of 22oC or less and a viscosity that is greater than or equals to 100 cP. Bitumen, hosted in oil sands (also referred to as tar sands) deposits, has viscosity greater than 10,000 cP and is typically in the hundreds of thousands to millions of cP. The majority of the world's heavy oil and oil sands deposits are in Venezuela and Canada. Owing to a relatively favorable viscosity, cold production, often associated with water injection, has been the
dominant heavy oil recovery method in Venezuela. Unfortunately, similar established primary oil recovery methods can seldom be extrapolated to extra heavy oil and bitumen reservoirs with any reasonable success. This is due to a combination of factors - notably, very low mobility (viscosity in excess of 106 cP for Athabasca bitumen) and very low solution gas energy.
As a result, several specialized recovery mechanisms are often employed for the primary recovery of heavy oil. Open-pit mining has traditionally been used to recover shallow bitumen (less than ~70 metres deep) in Canada. However, more than 77% (or 136 billion barrels) of the Canadian recoverable heavy oil reserves are at depths prohibitive to open-pit mining (ERCB, 2011), and therefore, require alternative technologies for economic recovery. For such reservoirs, the key aim is to raise in-situ oil mobility by reducing oil viscosity, and thermal recovery methods have emerged as a viable alternative. Thermal recovery methods are increasingly being utilized for primary recovery; buoyed by advancements in horizontal well technology and a reduced environmental footprint compared to open-pit mining.
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