激光破碎煤岩作用过程理论分析与实验研究

Theoretical analysis and experimental research on breaking process of laser drilling in coal and rock

激光钻井是一项高效、清洁、控向性能好的钻井新技术,在煤层气开发中潜力巨大。从激光破碎煤岩作用过程和循环气体两方面入手,在理论上分析了激光破碎煤岩的作用过程;以激光照射到煤岩表面的平均功率密度和激光照射时间为变量,再分别以空气和氮气为钻井循环介质,进行了激光破碎煤岩实验。实验结果与理论分析基本一致,具体表现为:在一定范围内,增加激光平均功率密度和激光照射时间将使钻井进尺深度增加,钻孔直径增大,热影响区域增大,有利于提高激光破碎煤岩钻进效率,而氮气循环和空气循环激光破碎煤岩各有优势,可进行交变循环钻进。

Laser drilling is a highly efficient, clean and controble new drilling technology, has great potential inCBM development. From the process of breaking coal and rock by laser and circulating gas, the paper analyzedtheoretically the action process of breaking coal and rock by laser, took the average power density and the timeof laser irridiation on coal and rock surface as variables, air and nitrogen as circulating medium, conductedexperiment of breaking coal and rock by laser. The experiment results were basically consitent with the theoreticalanalysis, showing concretely that within limits increasing the average power density and the time of laserirridiation would make the drilling footage and the borehole diameter as well as the heat-affected zone increase,which is favorable to enhance the drilling efficiency of breaking coal and rock by laser, while circulationof nitrogen and air for breaking coal and rock by laser each has advantages, and alternate circulationdrilling can be conducted.