聚乙烯对油田加热集输工艺的适用性

Applicability of Polyethylene to the Heating Gathering Process in the Oilfield

为明确非金属复合管聚乙烯内衬在油田加热输送工艺的适用性,借助反应釜、扫描电镜研究4731B聚乙烯挂片在温度50℃、压力0.1、4、6 MPa、采出原油与采出水介质中168 h内的渗透行为。研究发现,采出原油、采出水均可渗透进入聚乙烯使其溶胀、增重,采出原油引起的增重率大于采出水,最大为4.52%;聚乙烯表面产生裂纹,介质沿裂纹局部渗透,最大渗透深度达166.7μm;介质渗透使聚乙烯力学性能降低;采出原油引起的溶胀随压力增大而减小,采出水引起的溶胀在压力4 MPa时最严重;光氧老化对聚乙烯力学性能的影响显著高于介质渗透。结果表明,加热输送条件下,聚乙烯耐油田介质性能虽满足ISO 23936-1-2009要求,但裂纹现象与高裂纹扩展速率易导致非金属复合管泄漏失效。

In order to clarify the applicability of polyethylene liner of non-metallic composite pipe applied in the heating gathering process in the oilfield,the permeation behavior of 4731B polyethylene,which were immersed in the produced crude oil,produced water for 168 hours under the condition of 50℃,0.1,4,6 MPa,was studied by means of reactor and scanning electron microscope.The results show that the polyethylene could be penetrated by both the produced crude oil and the produced water,and penetration leads to swell and gain weight.The weight gain rate caused by the produced oil is higher than water,and the maximum is 4.52%.Cracks are observed on the surface of polyethylene.The media is found to penetrate into the cracks,and the maximal penetration depth is 166.7μm.The mechanical properties of polyethylene decrease with the penetration of two media.The swelling caused by the produced crude oil decreases with the increase of pressure,while the swelling caused by produced water is the most serious when the pressure is 4 MPa.The mechanical properties of polyethylene affected by photooxidation aging are significantly higher than medium permeation.The results show that although the performance of polyethylene in gathering medium meets the requirements of ISO 23936-1-2009,the crack phenomenon and high crack propagation rate can easily lead to the leakage failure of the non-metallic composite pipe.