Applicability of Polyethylene Liner of Oil Pipe in High Temperature and High Pressure H₂S Environment

Indoor corrosion tests simulating the field working conditions of Tahe Oilfield were carried out on polyethylene liner materials for oil pipe at different temperatures to investigate the performance changes of polyethylene in a high temperature high pressure H₂S environment, which were verified by field tests. The results show that polyethylene liner could be used in downhole working conditions below 80 ℃, and serious cracking failure occurred when the temperature was above 80 ℃. The main reason for cracking failure was the thermal oxidation aging of polyethylene because of high temperature and oxygen molecule. Polyethylene molecules underwent cracking, cross-linking and dehydrogenation and carbonization under the action of heat, resulting in cracking, pulverization or shrinkage deformation failure.