低渗透油藏CO₂埋存井筒泄漏风险评价模型

Leakage Risk Evaluation Model for Wells in the Process of CO₂ Storage in Low Permeability Reservoirs

摘要: 在CO₂地质埋存过程中，CO₂可能从井筒、断层、裂缝泄漏，也有可能通过分子扩散从储层和盖层溢出。但从井筒泄漏所造成的短期风险的影响较大，容易对井场的工作人员生产生活造成伤害，因此需要根据油藏和井筒的参数，建立CO₂泄漏规模、泄漏风险的评价模型。本文对鄂尔多斯盆地长庆油田某低渗透油藏注入CO₂井筒泄漏的危险性进行了研究，模拟CO₂从井筒泄漏后，采用有毒气体泄漏扩散的模型进行气体扩散后CO₂浓度的研究，结合二氧化碳泄漏扩散危害浓度临界值，确定二氧化碳扩散的影响区域。通过模型计算泄漏源附件区域划分为致命区、严重伤害区、不良反应区和安全区的距离和范围，并对低渗透油藏CO₂埋存井筒泄漏风险进行评价。

Abstract: In the process of Carbon Capture, Utilization, and Storage (CCUS), CO₂ may leak from wellbore, faults, cracks and fractures, and may also overflow from reservoirs and caprocks by molecular diffusion. The high concentration CO₂ from the wellbore leakage may cause great danger to the people’s life on the wellsite. Therefore, it is necessary to develop an evaluation model for CO₂ leakage. The risk of CO₂ wellbore leakage can be evaluated by the model of toxic gas leakage and diffusion. According to the gas diffusion concentration, the critical damage and toxicity value of CO₂ concentration, the influence region of CO₂ diffusion can be determined. Based on the simulation model, the leakage source area is divided into fatal region, heavy injury region, untoward effect region and safety region. The leakage risk of the CCUS is evaluated in a low permeability reservoir, in Changqing Oilfield, Ordos Basin, China. The forecast of the CO₂ leakage risk is then used to guide the installation of the near surface CO₂ concentration monitor and to design the CO₂ leakage disposal scheme.