Summary This study provides an extensive critical review of electromagnetic heating (EMH) methods [inductive heating (IH), low-frequency heating (LFH), and high-frequency heating (HFH)] to highlight their existing challenges in enhanced heavy-oil and oil sands recovery. In general, IH is considered to be less practicable than LFH and HFH. The resistance (ohmic or conduction) heating prevails in LFH while dielectric heating prevails in HFH. Thus, the effectiveness of LFH decreases if reservoir water is overheated to generate steam. Also, the intensity of the energy released and the temperature rise in LFH are not as significant as those in HFH. LFH also fails in penetrating the media with breaks, heterogeneities, and in partially saturated media (e.g., when some oil saturation has been produced). These challenges might somewhat be remedied by HFH at the expense of reducing the electromagnetic (EM) wave penetration depth. The advantages of HFH include remote heating through a desiccated reservoir region around the EM energy source, higher intensity of the energy released and greater temperature rise, and better EM wave penetration through partially saturated media with breaks and heterogeneities. The caveat, however, is that the practical application of HFH could be more expensive than LFH. Besides, the lower depth of EM wave penetration in HFH remains a challenge. During HFH, the temperature increase occurs as a result of the induced molecular rotation in the dielectric material, in particular if the material contains more polar compounds. The polar molecules follow the EM field. This increases the internal molecular friction within the material and generates heat, leading to the rise of temperature. Because the heat generated is a function of the stored (absorbed) energy in the reservoir, the dielectric constant or the real permittivity of the reservoir should be enhanced to enhance the performance of HFH. This ensures that the temperature has risen reasonably in a reasonable amount of time with a reasonable amount of electricity consumption. However, to generate a uniform rise in temperature on a large scale away from the wellbore, the imaginary permittivity of the material should be reasonably lowered, too, for maximizing the penetration of the EM wave (while the real permittivity is an indication of the degree of polarization, the imaginary permittivity is associated with dielectric losses). Lowering the imaginary permittivity away from the wellbore helps minimize the effects of steam condensation (condensate formation retards the EM wave propagation) or delay steam condensation because the reservoir temperature is reduced during the later stages of oil production. The thermal conductivity of the formation should also be enhanced, especially away from the wellbore to generate a more uniform rise in temperature. These three reservoir improvements (enhancing real permittivity, lowering imaginary permittivity, and enhancing thermal conductivity) in an attempt to enhance EMH underpin the rationale behind proposing future optimizations of EMH, and in particular, HFH.

中文翻译：

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用于重油和沥青回收的电磁加热：实验、数值和试点研究

总结 本研究对电磁加热 (EMH) 方法 [感应加热 (IH)、低频加热 (LFH) 和高频加热 (HFH)] 进行了广泛的批判性审查，以突出它们在强化稠油和油砂回收。一般来说，IH 被认为不如 LFH 和 HFH 实用。电阻（欧姆或传导）加热在 LFH 中占主导地位，而介电加热在 HFH 中占主导地位。因此，如果储层水过热产生蒸汽，LFH 的有效性就会降低。此外，LFH 释放的能量强度和温度升高不如 HFH 显着。LFH 也无法穿透具有断裂、非均质性的介质和部分饱和介质（例如，当已经产生了一些油饱和度时）。HFH 可能会在某种程度上解决这些挑战，但代价是降低电磁 (EM) 波的穿透深度。HFH 的优点包括通过 EM 能源周围干燥的储层区域进行远程加热，释放的能量强度更高，温度升高更大，以及 EM 波更好地穿透具有断裂和非均质性的部分饱和介质。然而，需要注意的是，HFH 的实际应用可能比 LFH 更昂贵。此外，HFH 中较低的 EM 波穿透深度仍然是一个挑战。在 HFH 期间，温度升高是由于介电材料中诱导的分子旋转而发生的，尤其是在材料包含更多极性化合物的情况下。极性分子跟随 EM 场。这增加了材料内部的分子摩擦并产生热量，导致温度升高。因为产生的热量是储层中存储（吸收）能量的函数，所以应提高储层的介电常数或实际介电常数以提高 HFH 的性能。这确保了温度在合理的时间内以合理的用电量合理上升。然而，为了在远离井筒的地方产生大范围的温度均匀上升，材料的假想介电常数也应该合理降低，以最大限度地提高 EM 波的穿透力（而实际介电常数是程度的指示）极化时，虚介电常数与介电损耗有关）。降低远离井筒的假想介电常数有助于最大限度地减少蒸汽冷凝的影响（冷凝水的形成会延迟 EM 波的传播）或延迟蒸汽冷凝，因为油藏温度在采油的后期阶段会降低。地层的热导率也应该提高，特别是远离井筒以产生更均匀的温度升高。这三项油藏改进（提高真实介电常数、降低假想介电常数和提高热导率）旨在增强 EMH，这支持了提出未来 EMH 优化的基本原理，特别是 HFH。