钢丝缠绕增强聚乙烯复合管集输服役后的承压性能

Pressure bearing capacity of polyethylene composite pipe reinforced by steel wires after gathering service

为探明钢丝缠绕增强聚乙烯复合管(简称复合管)在油田集输环境服役后的极限承压,以长庆油田第四采油厂试用的4731B型复合管、第五采油厂试用的防垢型复合管为研究对象,采用100 MPa耐压爆破实验机分别对新管、服役后现场管进行2组瞬态水压爆破对比实验,分析了爆破口的特征形貌及爆破压力,并借助应变数据采集系统记录爆破过程中管道不同位置的瞬时应变。结果表明:该类型复合管服役后的平均瞬时爆破压力有所降低,爆破口形貌发生显著变化,膨胀变形较新管显著增大;起爆前,应变随时间的变化分为零应变段、线性增长段、指数增长段共3个阶段;起爆后,应变发生振荡,直至稳定。究其原因可能是复合管施工期间钢丝与高密度聚乙烯基体之间的粘结剂局部失效所致。研究成果可为该类型复合管在集输油环境中服役时失效原因的分析提供借鉴。

In order to clarify the ultimate pressure bearing capacity of polyethylene composite pipe reinforced by steel wires(hereinafter referred to as composite pipe)used for oil gathering in oilfields,a study was performed on 4731B composite pipe tried in No.4 Oil Production Plant and the anti-scaling composite pipe tried in No.5 Oil Production Plant of Changqing Oilfield.In the study,2 groups of transient hydraulic fracturing experiment were performed respectively on the new pipe and the in-service pipe with a 100 MPa burst tester.Meanwhile,the break appearance and burst pressure were analyzed,and the instantaneous strains at different positions during the bursting process were recorded through a strain data acquisition system.The results indicate that the average instantaneous bursting pressure of this composite pipe in service is reduced to some extent,with the break appearance changed dramatically,and the expansion deformation increased significantly in comparison with the new pipes.Besides,the change of strain with time before bursting is divided into 3 stages,i.e.,zero strain stage,linear growth stage and exponential growth stage.However,the strain after bursting oscillates until it is stabilized.The reason might be the local failure of adhesive between the steel wire and the high-density polyethylene matrix during the construction of composite pipe.These results could provide reference for the failure analysis of this type of composite pipe applied in oil gathering environment.