Application of high-frequency alternating-current principles to develop practical induction well bore heaters for in-situ thermal ground remediation

加拿大政府列出了全加拿大23 670个地点，其中土壤和水中的污染物已得到补救或需要补救。仅在阿尔伯塔省，从1990年到2012年，大约有648万升碳氢化合物液体泄漏到土壤和水中。目前正在使用一些电和化学方法来修复这些碳氢化合物泄漏附近的污染土壤。电学方法包括使用插入地下的大型电极对受污染的土壤和水进行电热或电加热，这些电极由地面上的大型交流电源驱动。电热加热的优点是在不增加二次化学污染物的情况下解吸土壤中的碳氢污染物。对污染土壤进行电热加热的挑战来自于功率损失和在渗透性较差的土壤类型中热量穿透距离有限。最近，行业合作伙伴（McMillan-McGee Corp.）也开发了一种感应加热器，该加热器配备了线圈，可以产生交流频率远高于60 Hz的磁场，从而在周围的钢制井筒管套管壁上产生热量，从而更有效地加热土壤。与传统的60 Hz电极不同，表征和减轻高频下的损耗更具挑战性，因为损耗不仅是由于线圈导体损耗，还由于线圈的电场和磁场与周围井管柱的相互作用，以及周围地层的影响较小。对于电热应用，其中一些损耗转化为热量，有助于电加热过程，但另一些则抑制了沿着线圈的电力传递和传输。McMillan-McGee和卡尔加里大学已经形成了一项研究合作，研究和表征McMillan-McGee的新型高频电热感应加热器中的高频电损耗。在电热修复过程中，将10-80千瓦的功率水平送入井下加热器，表征并最小化这些损失对于更快地净化土壤和节省更多能源至关重要。

The Government of Canada lists 23,670 sites Canada-wide where contaminants in soil and water have been remediated or are in need of remediation. In Alberta alone, roughly 6.48 million liters of hydrocarbon liquids have leaked onto soil and water between 1990 and 2012. A few electrical and chemical methods are currently in use to remediate the contaminated soil in the vicinity of these hydrocarbon leaks. Electrical methods involve electro-thermal or electrical heating of contaminated soil and water using large electrodes inserted into the ground, which are driven using a large AC power source on the surface. Electro-thermal heating offers the advantage of desorbing hydrocarbon contaminants in soil without adding secondary chemical pollutants. Challenges with electro-thermal heating of contaminated soil come from power losses and limited heat penetration over distance in less permeable soil types. More recently inductive heaters fitted with coils that produce magnetic fields at AC frequencies much higher than 60 Hz to induce heat in the walls of surrounding steel wellbore pipe casings have also been developed by the industry partner (McMillan-McGee Corp.) for heating soil more effectively. Unlike conventional 60 Hz electrodes, characterizing and mitigating these losses at high frequencies is even more challenging since losses are expected to be due to not just coil conductor losses but also due to the interaction of the coil's electric and magnetic fields with the surrounding well-bore pipe, and to a lesser extent on the surrounding ground formation. For electro-thermal applications, some of these losses get converted to heat and assist with the electrical heating process but others inhibit electrical power transfer and transmission along the coils. McMillan-McGee and the University of Calgary have formed a research collaboration to study and characterize these high frequency electrical losses in McMillan-McGee's new higher frequency Electro-thermal inductive heaters. With power levels of between 10-80 kW sent down hole into the heaters during the electro-thermal remediation process characterizing and minimizing these losses becomes important for quicker decontamination of soil and saving more energy.