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超临界CO_2射流具有破岩门限压力低、效率高的特性.直旋混合射流兼具直射流和旋转射流的破岩优势.采用超临界CO_2流体调制形成直旋混合射流的方法,有望大幅提高破岩效率.为了揭示其独特的岩石损伤破坏机制,分别选取页岩、白云岩与砂岩3种不同岩心,开展超临界CO_2直旋混合射流冲蚀岩石实验,并通过扫描电镜手段,观测冲蚀孔的微观损伤形貌.结果表明:页岩冲蚀后几乎未发生宏观形变,仅造成了表面微观损伤,产生了微小裂隙;白云岩及砂岩冲蚀后岩心表面产生了冲蚀孔,矿物晶体自身及晶间发生断裂甚至破碎.基于扫描电镜结果,分析认为其岩石损伤机制可以分为两方面:一方面,直旋混合射流对岩石产生轴向冲击、径向拉伸与周向剪切的共同作用,容易使岩石产生裂隙;另一方面,超临界CO_2具有低黏度、强扩散以及可压缩的性质,可进入深层孔隙,通过多种机制产生微裂隙并扩展已有裂缝,最终造成岩石宏观破碎.
The supercritical CO_2 jet has the characteristics of low rock breaking threshold pressure and high efficiency.The direct jet mixed jet has the advantages of direct jet and rotary jet breaking rock.The method of supercritical CO_2 fluid modulation to form direct jet mixed jet is expected to increase dramatically Rock efficiency.In order to reveal its unique mechanism of rock damage damage, three different cores of shale, dolomite and sandstone were selected respectively to carry out experiments of supercritical CO_2 direct-jet mixed jet erosion lithology. Scanning electron microscopy was used to observe erosion holes The results show that there is almost no macroscopic deformation after shale erosion, only micro-damage on the surface and micro-cracks, and erosion holes on the core surface after dolomite and sandstone erosion, and the mineral crystals themselves And the intergranular fracture or even rupture.Based on the SEM results, the rock damage mechanism can be divided into two aspects: on the one hand, the direct impact of radial jet on the rock, radial tension and circumferential shear together On the other hand, supercritical CO 2 has the characteristics of low viscosity, strong diffusion and compressibility, and can enter deep pores. Through a variety of mechanisms Produce micro-cracks and expand the existing cracks, eventually resulting in macroscopic rock fragmentation.