| Description |
The primary objective of this project was to develop a downhole heater to raise oil shale to a specified temperature in-situ, and to recover energy-rich liquids and gasses. The project had two main phases. Phase I was a preliminary study investigating several different burner concepts for generating heat at great depth and over significant horizontal lengths. In Phase II, a unique configuration of a downhole heater was proposed that eliminates some of the issues regarding previously-considered configurations. The feasibility and applicability of the proposed heater were investigated by looking at key issues that have not been completely addressed in the literature by other researchers. First, calculations were performed to determine appropriate sizes for feeder pipes and nozzles, as well as the pressure distributions in different sections of the heater, so that a uniform flow distribution is maintained along the 2000 ft length of the heater. Then, the overall heat transfer coefficient in the heater and the required gas mixture temperature were determined based on design specifications. The average overall heat transfer coefficients of the outer annulus and the reaction chamber were estimated as 15 W/ (m2. K) and 3.5 W/ (m2. K). The average flue gas temperature was determined to be equal to 939 K. Second, a cold-flow study was performed to investigate the effect of nozzle spacing and orientation on the mixing behavior inside the heater. It was concluded the radial orientations of the nozzles have a more significant role in the mixing behavior than the axial positions. Finally, the effects of the diluents N2, CO2, and H2O on the oxidation behavior of methane-oxygen mixtures were investigated by CHEMKIN modeling studies and reaction sensitivity analysis. Thesestudies concluded that at low gas inlet temperatures, the flame temperature is mainly controlled by the thermal properties of the diluents, and the chemical effect of the diluents is almost negligible. As the heat capacity of the mixture increases, the reaction temperature and the flame speed drop, while the ignition delay time increases. Water vapor addition at a low initial temperature (800-900 K) and 30 atm promotes methane oxidation and decreases the ignition delay time. |
