Wellbore integrity is one of the most critical factors for CO₂ storage, subsurface resource extraction, and waste disposal. Wellbore integrity monitoring is challenging due to the general inaccessibility and high cost of well-logging operation in complex subsurface conditions. In this study, we tested a novel non-invasive approach for wellbore-integrity assessment based on time-domain reflectometry (TDR) method. With this method, a high-frequency electromagnetic pulse is sent into the borehole casing, and the reflected signals due to integrity-related impedance anomalies are recorded at the wellhead, providing rapid borehole integrity diagnosis without downhole deployment. Laboratory, numerical, and field experiments were conducted to prove the feasibility of this approach. The laboratory experiments with coaxial cable, resembling the typical wellbore, showed clear reflected signals from both of the damaged section and the end of the cable. Numerical sensitivity tests indicated that the TDR response is affected by the changes of the material in the borehole, including infilled fluids. Our field trial was conducted on an oil well (with a depth of 240 m) in the central valley region of southern California. The TDR records showed a clear reflection that matched both the calculated two-way travel time from the bottom of the borehole, as well as the numerical simulation. Our results suggested the feasibility of the TDR method for quick assessment of wellbore integrity based on wellhead only deployment.

井筒完整性是CO ₂的最关键因素之一储存，地下资源开采和废物处置。井眼完整性监控由于复杂的地下条件下普遍难以进入且测井作业成本高而具有挑战性。在这项研究中，我们测试了一种基于时域反射法（TDR）的新型非侵入性井眼完整性评估方法。使用这种方法，将高频电磁脉冲发送到井眼套管中，并且由于完整性相关的阻抗异常而产生的反射信号会记录在井口，从而无需井下部署即可快速进行井眼完整性诊断。进行了实验室，数值和现场实验以证明这种方法的可行性。实验室使用同轴电缆进行实验，类似于典型的井眼，在损坏的部分和电缆末端均显示清晰的反射信号。数值灵敏度测试表明，TDR响应受井眼材料（包括填充流体）变化的影响。我们的现场试验是在南加州中部山谷地区的一口油井（深度为240 m）上进行的。TDR记录显示出清晰的反射，与从井底算出的双向行程时间以及数值模拟相匹配。我们的结果表明，基于仅井口部署的TDR方法可快速评估井眼完整性的可行性。我们的现场试验是在南加州中部山谷地区的一口油井（深度为240 m）上进行的。TDR记录显示出清晰的反射，与从井底算出的双向行程时间以及数值模拟相匹配。我们的结果表明，基于仅井口部署的TDR方法可快速评估井眼完整性的可行性。我们的现场试验是在南加州中部山谷地区的一口油井（深度为240 m）上进行的。TDR记录显示出清晰的反射，与从井底算出的双向行程时间以及数值模拟相匹配。我们的结果表明，基于仅井口部署的TDR方法可快速评估井眼完整性的可行性。