Assessing the potential to use repeated ambient noise seismic tomography to detect CO2 leaks: Application to the Aquistore storage site
Assessing the potential to use repeated ambient noise seismic tomography to detect CO2 leaks: Application to the Aquistore storage site
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DOI：
10.1016/j.ijggc.2018.02.007
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发表时间：
2018-04
影响因子：
3.9
通讯作者：
A. Stork;C. Allmark;A. Curtis;J. Kendall;D. White
中科院分区：
文献类型：
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作者：
A. Stork;C. Allmark;A. Curtis;J. Kendall;D. White
加拿大萨斯喀彻温省的Aquistore项目为世界上第一个商业发电厂和碳捕获和储存（CCS）项目提供二氧化碳（CO2）储存。自2015年4月以来，已在3.2公里的深度注入CO2，永久性近地表地震检波器阵列提供被动地震监测。识别任何泄漏的能力是CO2储存场所风险管理和降低的重要组成部分。因此，我们调查的潜力，监测地震速度的变化后，假设泄漏的CO2从水库使用被动监测方法。我们估计预期的剪切波速度变化与CO2饱和度，并使用从检波器阵列的数据，我们调查是否环境噪声干涉（ANI）和瑞利波群速度图的层析反演可以提供一个合适的CO2泄漏检测工具。为了评估该方法的可重复性，我们进行，第一次，一个时间推移的环境噪声断层扫描调查的CO2存储网站，以涵盖时间段之前和之后的注入启动。敏感性分析结果表明，从目前的阵列配置获得的可用面波数据对水深400米和更浅的深度敏感。我们不希望在如此浅的深度观察到由于CO2迁移而引起的任何变化，并且估计的注入前后的地震速度在60 m s−1以内，这是预测的CO2饱和度速度变化的两倍。因此，由于旅行时间拾取的不确定性（5-15%）和连续几天之间获得的速度结构的变化（高达20%），我们将无法解决400 m处CO2涌入的预期地震速度变化（0.33 -4%）。此外，噪声源的可变性不允许在当前可用数据的时间范围内进行稳定的速度估计。因此，在Aquistore现场发生CO2泄漏的情况下，使用本文应用的标准环境噪声分析方法，只有当（a）更宽的孔径表面阵列就位以允许使用更长周期的表面波，在更大的深度提供灵敏度，（B）可以以增加的精度拾取干涉测量合成的表面波的到达时间，以及（c）在重复勘测之间存在噪声源分布的稳定性。然而，三维近地表速度的地图，在这项研究中获得的，仍然可以是有用的近地表静态校正时，使用有源地震反射调查的图像和监测的水库。更一般地说，需要进一步类似的研究，以评估ANI泄漏检测在其他CO2存储站点的适用性。
The Aquistore project in Saskatchewan, Canada provides carbon dioxide (CO2) storage for the world's first combined commercial power plant and carbon capture and storage (CCS) project. CO2has been injected at a depth of 3.2 km since April 2015 and a permanent near surface geophone array provides passive seismic monitoring. The ability to identify any containment breach is a vital part of risk management and reduction for CO2storage sites. We therefore investigate the potential to monitor seismic velocity changes following a hypothetical leak of CO2from the reservoir using passive monitoring methods. We estimate the expected shear-wave velocity change with CO2saturation, and using data from the geophone array we investigate whether ambient noise interferometry (ANI) and a tomographic inversion for Rayleigh wave group-velocity maps could provide a suitable CO2leakage detection tool. To assess the repeatability of the method, we conduct, for the first time, a time-lapse ambient noise tomography survey of a CO2storage site to cover time periods preceding and following injection start-up. Sensitivity analysis results indicate that usable surface wave data derived from the current array configuration are sensitive to depths of ∼400 m and shallower. We do not expect to observe any changes due to CO2migration at such shallow depths and the estimated seismic velocities pre- and post-injection agree to within 60 m s−1, which is on the order of double the predicted velocity change with CO2saturation. Therefore, due to uncertainties in travel-time picks (5–15%) and variations in the obtained velocity structure between consecutive days (up to 20%), we would be unable to resolve the expected seismic velocity change with an influx of CO2at 400 m (∼3–4%). Additionally, the noise source variability does not allow stable velocity estimates to be made in the time-frame of currently-available data. Consequently, in the event of a CO2leak at the Aquistore site, using the standard ambient noise analysis methods applied herein, Rayleigh wave tomography could be deployed to detect velocity changes due to CO2saturation only if (a) a wider aperture surface array was in place to allow longer period surface waves to be used, providing sensitivity at greater depths, (b) arrival times of interferometrically-synthesised surface waves could be picked with increased accuracy, and (c) there is stability of the noise source distribution between repeated surveys. However, a map of three-dimensional near surface velocities, as obtained in this study, could nevertheless be useful for near surface static corrections when using active-source seismic reflection surveys to image and monitor the reservoir. More generally, further similar studies are required to assess the applicability of ANI for leak detection at other CO2storage sites.