超临界CO_2直旋混合射流冲蚀岩石的损伤破坏机制  

Mechanisms of rock breaking by swirling-round SC-CO_2 jet

作　　者：田守嶒[1] 刘庆岭[1] 盛茂[1] 李根生[1] 王海柱[1] TIAN ShouCeng LIU QingLing SHENG Mao LI GenSheng WANG HaiZhu(State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum （Beijing）, Beijing 102249, China)

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249

出　　处：《中国科学：物理学、力学、天文学》2017年第11期74-83,共10页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然基金重大计划项目(编号:51490652)资助

摘　　要：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.Supercritical carbon dioxide （SC-CO2） jet is characterized by low rock breaking threshold pressure and high rock breaking rate. Swirling-round jet, taking the advantages of both swirling and round jet, enjoys high rock breaking efficiency.By integrating swirling-round jet and SC-CO2, it is prospective for swirling-round SC-CO2 jet to improve rock erosion efficiency further. Rock damage mechanisms of swirling-round SC-CO2 jet are investigated by means of rock-erosion experiments and scanning electron microscope （SEM） observation. The selected core samples include shale, dolomite as well as sandstone. For shale, no macro-deformation occurs and microscopic damage is discovered, forming tiny cracks.For dominate and sandstone, erosion holes form, and crystal particle cleavage as well as inter-particle rupture occur.According to the observation results, the rock damage mechanisms of swirling-round SC-CO2 jet are divided into two aspects. On the one hand, swirling-round SC-CO2 jet breaks rock by combining axial impinging, radical tension and circumferential shear. On the other hand, with characteristics of low viscosity, compressibility and strong diffusivity,numerous micro fractures are caused by SC-CO2, and existing fractures are expanded, which led to fractures joining together and massive rocks split off.

关 键 词：超临界CO2 直旋混合射流 损伤机制 扫描电镜 

分 类 号：TE21[石油与天然气工程—油气井工程]