Wang Zhijun, Wang Xiaojuan
State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University), Jiaozuo, Henan, People's Republic of China.
School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan, People's Republic of China.
Sci Rep. 2021 May 5;11(1):9618. doi: 10.1038/s41598-021-89193-5.
As a clean energy resource, coalbed methane (CBM) has drawn worldwide attention. However, the CBM reservoir has strong adsorption capacity and low permeability and thus requires stimulation. As a means to stimulate coalbed methane recovery, thermal injection faces geological and economic challenges because it uses conventional conductive heating (CH) to transfer heat. Realized by the conversion of the electromagnetic energy into the thermal energy, microwave heating (MH) may be a sound stimulation method. Although previous research suggested that MH had potential as a stimulation method for coalbed methane recovery, it is not clear if MH is superior to CH for enhancing coalbed methane recovery. This paper compares the effect of MH and CH on methane desorption from coal using purpose-built experimental equipment. To compare the MH and CH experimental results, the desorption temperature for each CH desorption test was set to the maximum temperature reached in the correlative MH desorption test. The results show that although the cumulative desorbed volume (CDV) of methane under MH was less than that desorbed by CH in the initial desorption stage, the final total CDV under MH for the three different power settings was ~ 12% to ~ 21% more than that desorbed by CH at the same temperatures. CH and MH both change the sample's microstructure but MH enlarges the pores, decreases methane adsorption, promotes methane diffusion, and improves permeability more effectively than CH. Rapid temperature rise and the changes in the coal's microstructure caused by MH were the main reasons for its superior performance. These findings may provide reference for selecting the most appropriate type of heating for thermal injection assisted coalbed methane recovery.
作为一种清洁能源，煤层气已引起全球关注。然而，煤层气储层具有很强的吸附能力和低渗透率，因此需要进行增产措施。作为提高煤层气采收率的一种手段，热注入面临地质和经济挑战，因为它使用传统的传导加热（CH）来传递热量。微波加热（MH）通过将电磁能转化为热能来实现，可能是一种可行的增产方法。尽管先前的研究表明微波加热作为提高煤层气采收率的增产方法具有潜力，但对于提高煤层气采收率而言，微波加热是否优于传导加热尚不清楚。本文使用专门建造的实验设备比较了微波加热和传导加热对煤中甲烷解吸的影响。为了比较微波加热和传导加热的实验结果，将每次传导加热解吸试验的解吸温度设定为相关微波加热解吸试验中达到的最高温度。结果表明，尽管在初始解吸阶段，微波加热下甲烷的累计解吸量（CDV）小于传导加热下的解吸量，但在三种不同功率设置下，微波加热最终的总CDV比相同温度下传导加热的解吸量高出约12%至约21%。传导加热和微波加热都会改变样品的微观结构，但微波加热比传导加热更有效地扩大了孔隙、降低了甲烷吸附、促进了甲烷扩散并提高了渗透率。微波加热导致的快速升温以及煤微观结构的变化是其性能优越的主要原因。这些发现可为热注入辅助煤层气采收选择最合适的加热方式提供参考。
