Experimental Investigation of the Transformation of Oil Shale with Fracturing Fluids under Microwave Heating in the Presence of Nanoparticles

Traditional methods of exploiting oil shale such as mining or in situ electric heating cause environmental pollution, and they have huge energy losses and high costs. These problems can be solved by combining microwave heating with hydraulic fracturing for the in situ exploitation of oil shale. In this study, an experimental microwave apparatus was manufactured for laboratory experiments. Different weight proportions of iron oxide nanoparticles (0.1, 0.5, and 1 wt %), microwave output power (600, 800, and 1000 W), and ultimate reaction temperatures (550, 750, and 950 °C) were taken into account in the design of an orthogonal experiment. Temperature distributions were influenced by microwave power, as well as by the concentration of iron oxide nanoparticles. The iron oxide nanoparticles facilitated a noticeable rise in the temperature of the oil shale in a short time. The experimental results confirmed the advantages of microwave heating, compared to conventional heating, in terms of temperature increases and improved yields of higher quality oil. Specifically, the oil collected under microwave irradiation contained more saturation and aromatics, and less sulfur and nitrogen, than that obtained by conventional heating. The highest oil yield and the best oil quality were obtained with the parameters of output power of 800 W, ultimate reaction temperature of 950 °C, and iron oxide nanoparticles at 0.1 wt %. Our findings contribute to the application of microwave technology to unconventional resources, and field tests at small scale should be supported.