聚能射流作用下固井水泥裂纹特征实验研究

Experimental Study on Crack Characteristics of Cementing Cement under the Action of Shaped Charge Jet

针对射孔完井作业中水泥环完整性失效,导致后续压裂过程中出现环空窜流的问题,通过柱形靶射孔实验模拟射孔弹对井筒的侵彻过程,借助数码显微镜与Nano Measurer软件对射孔后水泥石的裂纹特征及分布情况进行了显微观察分析,同时研究了水泥养护前浆体密度、射孔弹药型罩直径及地层围压等参数对射孔段水泥环裂纹特征的影响规律。结果表明:水泥第一界面受到射孔冲击后损伤程度明显大于第二界面,第一界面水泥石主要产生了3种裂纹:宏观主裂纹、螺旋状裂纹和径向微裂纹,且裂纹数量在孔道周围和靶体边缘较多。浆体密度的增加使得固井水泥第一界面裂纹数量和平均宽度均逐渐减小。射孔弹药型罩直径主要影响孔道周围螺旋裂纹数量。围压则主要影响水泥边缘径向裂纹数量。

In perforating and completion operation,the integrity failure of cement sheath leads to annulus channeling in the subsequent fracturing process.For solving this problem,the process of perforating wellbore and formation is simulated by cylindrical target perforating test,and the crack characteristics and distribution of the cement stone after perforating are observed and analyzed by means of the digital microscope and Nano Measurer software.At the same time,the influences of the parameters such as the density of cement slurry,the liner diameter of shaped charge and the formation confining pressure on the crack characteristics of the cement ring in the perforating section are studied.The results show that the damage degree of the first interface of cement is obviously greater than that of the second interface after perforation impact.There are three kinds of cracks in the first interface of cement:macro main crack,spiral cracks and radial micro cracks,and the number of cracks around the perforation channel and on the edge of the target is more.The number and average width of the cracks on the first interface of cement are decreased with the increase of cement slurry density.The liner diameter of shaped charge mainly affects the number of the spiral cracks around the perforation channel,while the confining pressure mainly affects the number of the radial cracks on the edge of cement.