A radiofrequency/microwave heating method for thermal heavy oil recovery based on a novel tight-shell conceptual design

摘要

The ongoing depletion of light oil resources and the increasing global energy demand is driving oil&gas companies towards the exploitation of unconventional oil resources. In order to extract crude oil from these resources, a sufficiently low oil viscosity must be achieved, for instance through temperature increase. Electromagnetic irradiation through downhole antennae can be a suitable method for in situ heating of reservoirs. Potential problems for this technique are the extremely high temperatures that can be reached at the well containing the radiating element and the strong dependence of temperature profiles on local variation of reservoir material properties. These problems can be solved to a large extent by inserting around the radiating well a tight shell made of a low loss dielectric material, and by selecting the proper irradiation frequency. The experimental work described in this paper aims to verify the effectiveness of a similar structure during the electromagnetic heating of over 2000 kg of oil sand in a sandbox up to 200 °C, using a dipolar antenna. Oil sand was irradiated at 2.45 GHz frequency with variable power (1-2 kW). The temperature in the oil sand mass and on the boundary were recorded throughout the test in several specific points, in order to estimate temperature profiles along the distance from the antenna. Experimental results confirmed that the presence of the low lossy material shell realized around the antenna is extremely efficient in lowering the temperature in this critical zone and in better distributing the irradiated energy in the oil sand mass.