超临界二氧化碳射流冲蚀页岩试验研究

RESEARCH ON EROSION OF SHALE IMPACTED BY SUPERCRITICAL CARBON DIOXIDE JET

超临界二氧化碳射流破碎页岩是一种极具前景的页岩气钻采方法。选取渝东南露头龙马溪组页岩,基于超临界二氧化碳射流破岩试验平台,开展不同冲击压力的超临界二氧化碳射流冲蚀页岩试验;采用CT、SEM/EDX、XRD、XRF等技术研究冲蚀前后页岩试样的变化规律。研究表明:(1)所选页岩具有低孔、高黏土含量和层理平行发育等特性;(2)超临界二氧化碳射流冲蚀后,页岩端面呈网格化破碎,整体呈大体积层状破碎;(3)超临界二氧化碳对页岩矿物具有腐蚀作用,导致页岩微观结构发生改变,降低了页岩的物理力学特性,有助于射流破岩。

Supercritical carbon dioxide(SC-CO2) jet is a prominent method in shale gas drilling for shale breaking. The shale sample of Longmaxi Formation was collected from the area southeast of Chongqing. On the experiment platform of SC-CO2 jet,the collected shale samples were shot with the SC-CO2 jets of varied jet pressures. The microscopic changes between the original and the eroded shale samples were studied utilizing CT,SEM/EDX,XRD and XRF methods. The collected shale samples were found to have low porosity,high clay mineral contents and parallel beddings. The surface of shale sample shot by SC-CO2 jet was broken grid-likely,and the sample was broken into layers of large volume overall. The erosion of shale mineral induced by SC-CO2 caused the changes of microstructure of shale,which reduced the mechanical strength of shale and was conducive to the rock breaking.