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

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.