固井缺陷对磨损套管抗内压强度的影响

Worn-casing burst strength after cement sheath defect

冯进 张慢来 李东海 孙仁俊

FENG Jin ZHANG Manlai LI Donghai SUN Renjun

长江大学机械工程学院，湖北荆州　434023

School of Mechanical Engineering, Yangtze University, Jingzhou 434023, China

套管磨损和固井缺陷是钻井过程中必然存在的现象。应用相似准则设计出磨损套管的相似模型，对不同固井质量缺陷和不同磨损情况的套管进行组合实验，将实验结果与有限元分析相结合来研究模型套管在不同固井缺陷和不同磨损量下的抗内压强度。将模型套管推广到原型，利用有限元方法分别计算了水泥环—套管—地层系统在不同水泥环缺失范围、不同套管磨损程度下的抗内压性能。研究结果表明：当水泥环有缺损时，不但不能增强套管的抗内压能力，反而降低了套管的抗内压强度。水泥环的缺失范围越小，应力集中现象越严重。

Casing wear and cementing defect are the inevitable phenomenon during drilling process. The similarity criterion is applied to design the similar model of the worn-casing. The combination experiments were executed for different cementing quality defects and different worn-casings. Then the result of the experiment and the finite element analysis are compared to study the model casing burst strength. Extending the model casing to prototype, finite element method is used to calculate the internal pressure strength of the cement-casing-formation system at different deficiency scope of cement sheath and different wear loss. The results show that the cement sheath would decrease the internal pressure strength of the casing, and the smaller the deficiency scope is, the greater the stress concentration is.