Magnetic Nanoparticles for Thermally Enhanced Heavy Oil Recovery
A novel method of delivering thermal energy efficiently to reservoirs for heavy oil production is described in this study. The method uses magnetic nanoparticles that generate heat locally when exposed to a high frequency magnetic field oscillation via hysteresis losses. This concept is currently used in medical research to thermally kill cancerous cells. Electromagnetic heating is an alternative method to heat heavy oil reservoirs without using water or steam. Using magnetic nanoparticles with electromagnetic heating would greatly reduce the energy requirement and would allow efficient propagation of heat into deeper regions beyond wellbore locality that are otherwise difficult to reach.
In this study, an alternating magnetic field is used to heat different types of dry and water dispersed nanoparticles and the temperature rise over time was measured. Two types of nanoparticles (NPs) generated the most amount of heating; pure Iron III Oxide (Fe304) and Fe304 mixed with Erbium (Er) in a 75% to 25% chemical ratio (Fe/Er 75-25). Fe304 and Fe/Er 75-25 samples were then prepared for different sizes and chemical compositions and were characterized for size using a nanosizer and Scanning Electron Microscope (SEM) images, morphology using X-ray Diffraction (XRD) analysis, chemical composition using Energy Dispersive Spectrometer (EDS) and hysteresis loop using a Super-conducting Quantum Interference Device (SQUID) test. Bitumen was used to simulate heavy oil conditions in which the nanoparticles were dispersed to create a nano ferro-fluid. The particles were then dispersed in bitumen samples and the effect of varying concentration, particle size and chemical ratio (50% and 75% Erbium) on heating efficiency was examined. The tested particle sizes were in the range of 40-120 nm which means they were all above the critical size for superparamagnetism (~27nm for the particle investigated in this study) and hence all heating generated by the NPs was attributed to hysteresis losses.
Characterization revealed high crystallinity of pure Fe304 samples and a tendency of crystallinity to decrease as the percentage of Erbium added to Fe304 is increased. SEM images revealed a tendency of the particles to aggregate as the percentage of Erbium increased. Except for Fe/Er 75-25, heating experiments revealed a negative relationship between concentration of NPs and Specific Absorption Rate (SAR); as concentration of
NPs increased the SAR decreased. For NP size, the results followed a common trend; SAR increased when NP size was decreased. In terms of chemical composition, it was revealed that the optimal percentage of Er added to Fe304 to enhance its heating capability was 25% whereas any increase in Er % beyond that point caused a proportional decrease in SAR.