Electromagnetic waves as a mechanism of heat generation in the reservoir is a concept that has great potential to efficiently produce heavy oil and bitumen. However, as a result of large wave attenuation, the penetration depth of the wave is relatively small. This limits the economic viability of an otherwise technically proven technology. Taking advantage of the inherent piezoelectric phenomenon in quartz crystals enables the manipulation of the penetration depth of the wave. Acoustic waves were introduced simultaneously with a microwave to the core samples where the presence of the mechanical wave generated an infinitesimal stress. Mechanical stress achieved by the acoustic wave triggered piezoelectricity in two sandstone samples with a limestone sample serving as the control. All consolidated core samples were fully saturated with either oil or water to capture the effect of the pore space. The incremental stress manifests itself through change in the complex permittivity of the sample measured with a vector network analyzer. The penetration depth of the microwave was calculated as a function of the measured complex permittivity. Comparative analysis of the penetration depth of the varying imposed stress states illustrates the additive penetration achieved due to piezoelectricity. Piezoelectricity as the fundamental mechanism of penetration increase was further demonstrated by isolation of the quartz contribution through use of the limestone. Increase in penetration depth was realized for all oil-saturated sandstone cores. The presence of the acoustic wave introduced a stress component across the quartz crystals, generating a change in the electric potential. This created a dynamic polarization that corresponded to an absorption environment more conducive to microwave penetration.

Electromagnetic waves as a viable means of introducing heat energy to reservoirs to allow for transmission of heavy or extra-heavy oil have been gaining prominence and notoriety in recent years due to its applicability to a wide variety of reservoirs. However, how reservoir properties affect the electromagnetic wave penetration is not well defined. This study investigates the impact of different reservoir rock and fluid combinations on the electromagnetic wave penetration and also introduces the dependency of dielectric properties on pressure. Several different reservoir rock samples (quartz rich, carbonate rich) with varying lithology and porosity were used in this study. The contribution of the fluid type was investigated by saturating the cores with water as well as measuring the responses on dry cores as a control. Air and water saturated rock samples were irradiated electromagnetically at varying frequencies (200 MHz to 6 GHz) under pressure. Frequency dependent dielectric properties were measured for each sample utilizing a coaxial dielectric probe and a vector network analyzer. Dielectric constant (ε′), loss index (ε″), and loss tangent of test mediums were utilized to generate the penetration depth of each sample as a function of frequency. The loss index and dielectric constant comprise the complex permittivity which is the foundation for microwave absorbance and penetration depth. Penetration depth is highly frequency dependent and exhibits an exponential decay where as the wave travels further into the sample more energy is gradually absorbed by the material and thus the energy content of the wave continually diminishes. With lower frequencies, higher penetration depth was obtained for all samples where less energy has been dissipated and absorbed by the formation. The utilization of both water and air represent both a very effective absorber of microwaves as well as a material transparent to microwaves respectively. Therefore, the dry cores (air saturated) realized greater penetration depths as less attenuation occurred due to the transparent nature of the saturating fluid. The quartz rich sandstone achieved lower penetration depths than the limestone core utilized which is indicative of greater capability of the sandstone samples to absorb microwave energy. Reservoir properties will affect the dielectric response of the material and so it becomes necessary to account for the presence of pressure due to overburden while taking laboratory measurements. The pressurized samples for both the sandstones were found to cause disparity between the control experiments when saturated with water. Introducing pressure of the water saturated sandstone samples effectively lowers the loss tangent resulting in a decreased capability to absorb microwave energy.

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Microwave heating has great potential to recover heavy oil reservoirs, because it significantly reduces the heating time and consequently the cost of heavy oil extraction. Moreover, heavy crude oils contain high amounts of polar molecules (asphaltenes) and polar functional groups, making them great microwaving candidates. This study investigates the microwave effectiveness for a specific heavy oil reservoir focused on its polar components. Furthermore, the impact of asphaltene precipitants and dispersants on microwave efficiency was investigated. A crude oil sample from Canada was subjected to microwave experiments for 30 seconds. Dielectric properties of the crude oil before and after exposure to microwave were mostly measured by using a vector network analyzer to quantify the overall polarity changes in the bulk crude. The impact of asphaltene precipitants (nC5 and nC7) and a dispersant (toluene) on microwave efficiency was also investigated. The crude oil sample was blended with nC5, nC7, or toluene at three varying doses (10%, 20%, or 50%) to investigate the impact of solvent dose on microwave efficiency. Microwave absorption and penetration depth were calculated to quantify the effectiveness of microwave heating. It has been observed through dielectric property measurements that microwave energy was absorbed by mainly the asphaltenes. Dielectric constant and loss tangent values of the blends prepared with asphaltene precipitants (nC5 and nC7) and toluene were measured before and after exposure to microwave to quantify the microwave absorption in different blends. Although precipitant mixtures had higher dielectric constants, the dispersant mixtures had much higher microwave absorption due to higher loss tangents. This finding was further supported by penetration depth measurements, in which dispersant mixtures had lower values, which led to higher microwave absorption of the crude oil mixtures. Microwave heating as a thermal enhanced oil recovery method is promising, however, complicated due to the uncontrollable nature of microwave penetration and absorption. This study reveals that while injection of an asphaltene precipitant to the desired reservoir locations can enhance the microwave penetration, injection of asphaltene dispersants will increase the microwave absorption. Cyclic injection of asphaltenes dispersants and precipitants may achieve the creation of effective heating spots within the reservoir by using only one microwave source.