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1. Corrosion of downhole tools and pumping rods: The corrosion of downhole tools in oil production wells becomes severe once free water appears in the wells. Due to the fact that the sucker rods, pistons, valves, etc. are in motion, they suffer greater damage. In oil wells with high water content and high H2S levels in the water, rod breaks often occur due to reasons such as corrosion fatigue, hydrogen embrittlement, and stress corrosion. In addition, corrosion also has an impact on the durability of sucker rods, with the parts most susceptible to wear being the couplings that connect the sucker rods. 2. Internal corrosion of oil pipes and casings: Internal corrosion in oil and casing pipes is mainly caused by CO2, H2S, and produced water. 3. External corrosion of the casing: Corrosion of the oil well casing occurs due to formation water and sulfate-reducing bacteria. Since the water layer was not sealed during cementing, the outer wall of the casing was exposed to water; remaining in a state of stagnant water with low oxygen levels for an extended period, sulfate-reducing bacteria multiplied in large numbers, causing severe corrosion and leading to the rupture of the casing. After the corrosion products are stripped away, a fresh steel surface is revealed, appearing as large, uneven masses, honeycombs, grooves, and bulges in a nodular shape. The entire surface of the casing resembles the marks left by termites eating through wood; the couplings are corroded and damaged, exposing the threads of the casing.