Radio Frequency Heating combined with Solvent Extraction- A method for oil recovery from surface oil sands

Trinidad has oil sands resources of about 2 billion barrels of oil on land. However, due to the relatively small extent and surface location (about 10,000 acres and with depths varying from surface to less than 500 feet), large scale surface mining and in-situ methods such as SAGD and VAPEX that are applied to recover oil from Canadian oil sands, are not practical. From experimental and simulation studies conducted, a new method was developed to commercially recover oil from Trinidad's surface oil sands. The open literature shows Radio Frequency Heating (RFH) to be more practical than electrical resistive heating (ERH) for surface oil sands. RFH is cheaper, quicker and heating is uniform and deeper than ERH, with oil recoveries ranging from 50 to 80%. Experimental studies show the viscosity of Trinidad oil sand oil to be greater than 10,000 cp and temperatures greater than 170 degrees C are required for the oil to flow. The power requirement for applying RFH at this temperature is greater than 25 kW (kW) and very costly. In addition, vaporisation of oil components occurs at these high temperatures, which is not environmentally safe for surface application. This new oil recovery method uses RFH at low power (1 kW) with a locally extracted organic solvent. The RFH system designed and assembled consists of an RFH chamber, signal generator and low power amplifier (1 kW). Samples of oil sands were heated in the chamber to 100 degrees C using a low frequency of 11.5 MHz and a citrus oil extracted in house was injected. Bitumen recoveries in the range 60-70% were achieved after three cycles of solvent injection and RFH. Experimental studies conducted show that Trinidad oil sands have a clay content in the range of 10-20%, are water wetting with a water saturation in the range 10-20% and have relative permittivities in the range 38-100. From this data, a new mathematical correlation was developed to obtain permittivities of oil sands which can be used with industry software to simulate oil recovery by RFH. Simulation studies show that for a 70% recovery from three cycles, eight gallons of solvent per cycle are required with RFH at a temperature of 100 degrees C. The data from the experimental and simulation studies show that with a heating cost of 2.50 USD to produce a barrel of oil, a solvent cost of 16 USD/barrel and with drilling, equipment and operational costs, and this method is viable at an oil price over 25 USD/barrel. The low cost and minimal environmental impact of this new method makes it very attractive for oil extraction from surface oil sands.