Review: Role of chemistry, mechanics, and transport on well integrity in CO2 storage environments
Review: Role of chemistry, mechanics, and transport on well integrity in CO2 storage environments
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DOI：
10.1016/j.ijggc.2016.01.010
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发表时间：
2016-06-01
影响因子：
3.9
通讯作者：
Zhang, Liwei
中科院分区：
文献类型：
--
作者：
Carroll, Susan;Carey, J. William;Zhang, Liwei
在与深层地质构造中的CO2储存相关的各种风险中，威尔斯是流体泄漏和地下水污染的重要潜在途径。注入CO2将扰乱储层，穿透CO2或压力足迹的任何威尔斯井都是CO2和/或储层盐水泄漏的潜在途径。对于具有长期石油和天然气勘探历史的地区来说，井漏尤其令人担忧，因为它们是二氧化碳地质储存地点的最佳候选者。本文详细探讨了威尔斯井保持其完整性的能力，对泄漏的耦合物理和化学过程进行了仔细的检查。了解随时间变化的泄漏是复杂的流体流动的变化，溶质运移，化学反应，机械应力超过十年或更长的时间范围内的现场操作和monitoring.Almost所有的研究都是基于实验室的泄漏的潜力，因为有有限的数据现场规模的泄漏。室内实验表明，CO2和CO2饱和盐水在发生扩散泄漏时，仍与水泥和套管发生反应。然而，降解速率受运输限制，水泥和套管性能的改变很低。当由于水泥收缩或压裂、界面（例如套管/水泥或水泥/岩石）沿着的间隙或套管失效而已经存在泄漏路径时，化学和机械变化有可能降低或增加泄漏风险。实验室实验和数值模拟表明，矿物沉淀或应变诱导裂缝的闭合可以随着时间的推移密封泄漏路径，或者相反地打开路径，这取决于流速、化学和应力状态。钢/水泥和水泥/岩石界面的实验表明，金属钝化、化学蚀变、机械变形和孔隙堵塞等保护机制也有助于减轻渗漏。蚀变的具体速率和性质取决于水泥、盐水和注入流体的成分。例如，共注入气体（如O-2、H2S和SO2）和火山灰改良剂（飞灰）对水泥的存在影响水泥反应的速率和性质。一个更完整的理解与密封和打开泄漏pathways的耦合物理化学机制是必要的，一个重要的挑战是采取经验为基础的化学，机械和运输模型在这里审查，并评估在现场规模的碳储存泄漏风险。伴随实验室和模拟研究的现场观察对于验证对泄漏风险的理解至关重要。由于材料类型（水泥、地质材料、套管）、现场条件（压力、温度、电位梯度、停留时间）和泄漏流体成分（CO2、共注入气体、盐水）的变化很大，现场规模的长期风险是一个积极研究的领域。特别令人感兴趣的是密封和其他保护机制可能有效的情况，它们可能失效的情况，以及这两个极端之间的不确定区域。(C)2016作者爱思唯尔有限公司出版
Among the various risks associated with CO2 storage in deep geologic formations, wells are important potential pathways for fluid leaks and groundwater contamination. Injection of CO2 will perturb the storage reservoir and any wells that penetrate the CO2 or pressure footprints are potential pathways for leakage of CO2 and/or reservoir brine. Well leakage is of particular concern for regions with a long history of oil and gas exploration because they are top candidates for geologic CO2 storage sites. This review explores in detail the ability of wells to retain their integrity against leakage with careful examination of the coupled physical and chemical processes involved. Understanding time-dependent leakage is complicated by the changes in fluid flow, solute transport, chemical reactions, and mechanical stresses over decade or longer time frames for site operations and monitoring.Almost all studies of the potential for well leakage have been laboratory based, as there are limited data on field-scale leakage. Laboratory experiments show that CO2 and CO2-saturated brine still react with cement and casing when leakage occurs by diffusion only. The rate of degradation, however, is transport-limited and alteration of cement and casing properties is low. When a leakage path is already present due to cement shrinkage or fracturing, gaps along interfaces (e.g. casing/cement or cement/rock), or casing failures, chemical and mechanical alteration have the potential to decrease or increase leakage risks. Laboratory experiments and numerical simulations have shown that mineral precipitation or closure of strain-induced fractures can seal a leak pathway over time or conversely open pathways depending on flow-rate, chemistry, and the stress state. Experiments with steel/cement and cement/rock interfaces have indicated that protective mechanisms such as metal passivation, chemical alteration, mechanical deformation, and pore clogging can also help mitigate leakage. The specific rate and nature of alteration depend on the cement, brine, and injected fluid compositions. For example, the presence of co-injected gases (e.g. O-2, H2S, and SO2) and pozzolan amendments (fly ash) to cement influences the rate and the nature of cement reactions. A more complete understanding of the coupled physical-chemical mechanisms involved with sealing and opening of leakage pathways is needed.An important challenge is to take empirically based chemical, mechanical, and transport models reviewed here and assess leakage risk for carbon storage at the field scale. Field observations that accompany laboratory and modeling studies are critical to validating understanding of leakage risk. Long-term risk at the field scale is an area of active research made difficult by the large variability of material types (cement, geologic material, casing), field conditions (pressure, temperature, gradient in potential, residence time), and leaking fluid composition (CO2, co-injected gases, brine). Of particular interest are the circumstances when sealing and other protective mechanisms are likely to be effective, when they are likely to fail, and the zone of uncertainty between these two extremes. (C) 2016 The Authors. Published by Elsevier Ltd.