Microwave Dielectric Properties of Heavy Oil and Heating of Reservoirs

Abstract

Abstract We have measured the electromagnetic high frequency (~5 GHz) response of heavy oil (API density ~10). The measurements were obtained for oil samples enclosed in high purity quartz vials located in an aluminum cylindrical resonator excited at the TE011 mode by means of microwaves. The oil relative real permittivity e' is found to be of the order of 2.3 with a loss tangent ranging from 0.0005 to 0.00006 depending on the frequency and the oil sample. We model the heating of reservoirs located at depths of the order of 1000 meters, excited through a cylindrical waveguide (a 6 inch diameter production pipe or a coiled tubing) excited in the TE01 mode. We discuss why this mode was selected and we analyze the attenuation due to various modes in cylindrical waveguides. The reservoirs considered have variable thicknesses (of the order of several meters). We present results for oil having the permeability of free space, and relative permittivities in the range from e = 2.3-j0.001, to e = 2.3-j0.01. The losses in the metallic circular waveguide walls reduce the surface applied power of 1 Kw to some 200 watts at the top of the reservoir and the mismatch between the empty and the filled waveguide further reduces the applied power due to the impedance mismatch. The power absorbed by the oil in the reservoir increases the temperature in the range of 8 to 20 C. This increase would certainly decrease the oil viscosity, favoring an easier production, but is far too small to cause any upgrading process. We include a discussion of the EROI factor (energy return on energy input) associated with electrical heating of oil reservoirs at low (60 Hz) frequencies and for the high frequency microwave heating process described.