Browsing College of Engineering and Mines (CEM) by Subject "Heavy oil"
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Electromagnetic heating of unconventional hydrocarbon resources on the Alaska North SlopeThe heavy oil reserves on the Alaska North Slope (ANS) amount to approximately 24-33 billion barrels and approximately 85 trillion cubic feet of technically recoverable gas from gas hydrate deposits. Various mechanisms have been studied for production of these resources, the major one being the injection of heat into the reservoir in the form of steam or hot water. In the case of heavy oil reservoirs, heat reduces the viscosity of heavy oil and makes it flow more easily. Heating dissociates gas hydrates thereby releasing gas. But injecting steam or hot water as a mechanism of heating has its own limitations on the North Slope due to the presence of continuous permafrost and the footprint of facilities. The optimum way to inject heat would be to generate it in-situ. This work focuses on the use of electrical energy for heating and producing hydrocarbons from these reservoirs. Heating with electrical energy has two variants: high frequency electromagnetic (EM) heating and low frequency resistive heating. Using COMSOL ® multi-physics software and hypothetical reservoir, rock, and fluid properties an axisymmetric 2D model was built to study the effect of high frequency electromagnetic waves on the production of heavy oil. The results were encouraging and showed that with the use of EM heating, oil production rate increases by ~340% by the end of third year of heating for a reservoir initially at a temperature of 120°F. Applied Frequency and input power were important factors that affected EM heating. The optimum combination of power and frequency was found to be 70 KW and 915 MHz for a reservoir initially at a temperature of 120°F. Then using CMG-STARS ® software simulator, the use of low frequency resistive heating was implemented in the gas hydrate model in which gas production was modeled using the depressurization technique. The addition of electrical heating inhibited near-wellbore hydrate reformation preventing choking of the production well which improved gas production substantially.
Reservoir simulations integrated with geomechanics for West Sak ReservoirGeomechanics is the study of the mechanical behavior of geologic formations. Geomechanics plays an important role in the life of a well. Without a proper understanding of the geomechanics of a reservoir, the projects associated with it may run into problems related to drilling, completion, and production. Geomechanics is important for issues such as wellbore integrity, sand production, and recovery in heavy oil reservoirs. While studying geomechanics, proper weight is given to mechanical properties such as effective mean stress, volumetric strain, etc., and the changes that these properties cause in other properties such as porosity, permeability, and yield state. The importance of analyzing geomechanics increases for complex reservoirs or reservoirs with heavy oil. This project is a case study of the West Sak reservoir in the North Slope of Alaska. Waterflooding has been implemented as enhanced oil recovery method in the reservoir. In this study, a reservoir model is built to understand the behavior and importance of geomechanics for the reservoir. First, a fluid model is built. After that, reservoir simulation is carried out by building two cases: one coupled with geomechanics and one without geomechanics. Coupling geomechanics to simulations led to the consideration of many important mechanical properties such as stress, strain, subsidence etc. Once the importance of considering geomechanical properties is established, different injection and production pressure ranges are used to understand how pressure ranges affect the geomechanical properties. The sensitivity analysis defines safer pressure ranges contingent on whether the formation is yielding or not. The yielding criterion is based on Mohr's Coulomb failure criteria. In the case of waterflooding, injection pressure should be maintained at 3800 psi or lower and production at 1600 psi or higher. And if injection rates are used as the operating parameter, it should be maintained below 1000 bbls/day. It is also observed that injection pressure dominates the geomechanics of the reservoir.
Scaling laws in cold heavy oil production with sand reservoirsThis thesis presents a rigorous step by step procedure for deriving the minimum set of scaling laws for Cold Heavy Oil Production with Sand (CHOPS) reservoirs based on a given set of physical equations using inspectional analysis. The resulting dimensionless equations are then simulated in COMSOL Mutiphysics to validate the dimensionless groups and determine which groups are more significant by performing a sensitivity analysis using a factorial design. The work starts simple by demonstrating how the above process is done for 1D single-phase flow and then slowly ramps up the complexity to account for foamy oil and then finally for wormholes by using a sand failure criterion. The end result is three dimensionless partial differential equations to be solved simultaneously using a finite element simulator. The significance of these groups is that they can be used to extrapolate between a small scale model and a large scale prototype.