渭北区块煤层气井抽油杆腐蚀影响因素

Corrosion behavior analysis of sucker rod for coalbed methane wells in the eastern block of Ordos basin

为明确鄂尔多斯盆地东缘渭北区块H矿区煤层气井腐蚀影响因素,以抽油杆为研究对象,通过对实际开采过程中产出气、采出水、抽油杆表面腐蚀产物成分和抽油杆质量损失检测分析,总结了抽油杆腐蚀类型和腐蚀强度,并对比分析了不同排采阶段、开发层系和采出液矿化度对抽油杆腐蚀的影响。研究结果表明:渭北区块煤层气井抽油杆主要受到CO2和H2S的腐蚀,其来源主要为5号煤和11号煤。在初期排水阶段抽油杆腐蚀程度低,主要是由少量CO2溶解气引起;憋套压和产气之后,抽油杆受到产出的酸性气体CO2和H2S的共同腐蚀作用,且腐蚀不断增强;同时地层水矿化程度对抽油杆腐蚀有明显的促进作用。由于腐蚀影响因素复杂且强度不断变化,因此,对抽油杆表面进行包覆或涂上防腐层是直接有效的防腐手段。

In order to make clear the corrosion rule of sucker rod for coalbed methane wells in the eastern block of Ordos basin,the paper summarizes the corrosion types and corrosion intensities of the sucker rod,based on the test of produced gas,produced water,corrosion products and weight loss of sucker rod.The paper analyzes the effect of different drainage stages,coal seam and mineralization degree of water on the corrosion.The results of the research indicate that corrosion is mainly caused by CO2 and H2S originated from No.5 coal seam and No.11 coal seam.The corrosion intensity is low in the early stage of dewatering,and it is caused by amount of dissolved CO2 gas.In the stage of co-production of water and gas,and in the stage of single phase gas production,the corrosion results from the synergistic reaction of CO2 and H2S and the intensity is enhanced,while the mineralization degree of water has an positive effect.Because of the complex corrosion influence factors and the constant change of strength,it is a simple and effective anticorrosive method to coat or use anticorrosive coating on the surface of sucker rod.