岩石表面激光射孔实验研究

Experimental Study of Laser Perforation on the Surface of Sandstone

采用高能激光束照射岩石表面,研究花岗岩和砂岩激光照射后形貌、物相及抗钻特性。结果表明,花岗岩表面明显破裂,生成透明玻璃釉物质。XRD分析可知,激光照射后花岗岩仍由石英、斜长石、钠长石、伊利石、铁白云石及方解石组成,孔内转化物由石英、斜长石、钠长石组成,而透明玻璃釉由石英和斜长石组成。砂岩表面激光射孔后,由灰色瓷釉层和褐色热影响区组成,其中褐色热影响区由石英和高岭石组成。激光照射花岗岩的破碎机制为热应力破碎,而砂岩表面并未产生裂纹,激光热作用的贡献主要是使砂岩熔化和气化。经PDC钻头钻进后,激光照射后砂岩可钻性变化不大,而花岗岩的可钻性级数明显降低。

The rock surfaces were irradiated by the high-energy laser beam,and the crack mechanism and drillability of granite and sandstone undergoing laser thermal effects were studied. The results show that obvious surface crack appears on the surface of granite and transparent glass glaze materials are formed. As it is seen from XRD analysis,the laser irradiated granite is composed of quartz,plagioclase,albite,illite,ankerite and calcite. However,the transformation product consists of quartz,plagioclase and albite,and the transparent glass glaze material is identified as quartz and plagioclase. Moreover,after laser drilling the sandstone surfaces are composed of gray enamel layer and brown heat affected zone( HAZ),while the brown HAZ is composed of quartz and kaolinite. During laser irradiation,the breakdown mechanism of granite is resulting from thermal stress,but there is no cracks on the surface of sandstone,the laser thermal heating mainly contribute to the melting and gasification of sandstone,which bring a clean hole. Undergoing the PDC bit drilling,drillability of sandstone after laser irradiation has little change,while which of granite decreased obviously.