老气田CCUS-EGR井筒水泥环腐蚀机理实验研究

Experimental Study on the Corrosion Mechanism of Cement Sheath in Wellbores of Old Gas Fields with CCUS-EGR

摘要: 本文针对碳捕集、利用与封存(CCUS)工程中井筒水泥环在酸性环境下的腐蚀问题，开展了模拟CCUS井实际工况下水泥腐蚀实验研究。实验深度还原井下高温高压环境(150℃、75 MPa)，在含12% CO₂和5 ppm H₂S的酸性环境中对水泥石进行为期一个月的腐蚀实验。系统分析CO₂、H₂S联合腐蚀作用下水泥石渗透率、腐蚀深度、微观形貌、物相组成及抗压强度等参数发展规律，结果表明：腐蚀后水泥石渗透率由0.125 md降低至0.0643 md；平均腐蚀深度为5.70 mm；微观结构显示腐蚀区域碳酸钙含量显著增加，并未检出硫化物；抗压强度由38.5 MPa降至21.0 MPa。研究结果为CCUS井水泥环完整性评价提供了实验依据。

Abstract: Aiming at the corrosion problem of wellbore cement sheaths in acidic environments within Carbon Capture, Utilization and Storage (CCUS) projects, this paper conducted an experimental study on cement corrosion by simulating the actual downhole conditions of CCUS wells. The experiment replicated the high-temperature and high-pressure downhole environment (150˚C, 75 MPa), and cement specimens were subjected to a one-month corrosion test in an acidic environment containing 12% CO₂ and 5 ppm H₂S. A systematic analysis was performed on the development patterns of parameters such as permeability, corrosion depth, microscopic morphology, phase composition, and compressive strength of the cement under the combined corrosive effects of CO₂ and H₂S. The results indicate that after corrosion, the permeability of the cement decreased from 0.125 md to 0.0643 md; the average corrosion depth was 5.70 mm; microstructural analysis showed a significant increase in calcium carbonate content in the corroded area, with no sulfides detected; and the compressive strength dropped from 38.5 MPa to 21.0 MPa. The findings of this study provide an experimental basis for the integrity evaluation of cement sheaths in CCUS wells.