Cross-well seismic waveform tomography for monitoring CO2 injection : a case study from the Ketzin Site, Germany
Cross-well seismic waveform tomography for monitoring CO2 injection : a case study from the Ketzin Site, Germany
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DOI：
10.1111/j.1365-246x.2012.05375.x
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发表时间：
2012-04
影响因子：
2.8
通讯作者：
Fengjiao Zhang;C. Juhlin;C. Cosma;A. Tryggvason;R. Pratt
中科院分区：
文献类型：
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作者：
Fengjiao Zhang;C. Juhlin;C. Cosma;A. Tryggvason;R. Pratt
地震全波形反演（波形层析成像）是一种利用地震资料高分辨率重建地下速度场的方法。该方法在20世纪80年代首次引入，并且在20世纪90年代后期当该方法在频域中实现时在计算上变得可行。这项工作提出了三个案例研究和一个合成基准的全波形反演应用。其中两个案例研究的重点是在Ketzin CO2地质储存场获得的时移井间和二维反射地震数据集。这些研究是CO2SINK和CO2MAN项目的一部分。结果表明，波形层析成像比走时层析成像更有效的CO2注入监测在Ketzin网站的跨井几何。对于地面数据集，我们发现它是很难恢复的速度异常的真实值，由于注入使用波形反演方法，但它是可能的定性定位注入CO2的分布。结果符合预期的基础上，传统的二维CDP处理方法和更广泛的三维CDP处理方法在该地区。进一步研究了地震全波形反演的可行性和效率，用于使用合成数据集的反射地震几何学对陆上CO2地质储存场地进行时移监测。结果表明，在监测CO2注入时，波形反演可以很好地补充标准CDP处理。波形反演的方法和策略的选择在很大程度上取决于CO2注入的时间推移监测的目标。最后一个案例研究是应用全波形反演方法在瑞典中东部的Forsmark站点的两个弯曲的配置文件。这项研究的主要目的是帮助确定所观察到的反射是否主要是由于流体填充的断裂带或基性岩床。这里的一个主要困难是，剖面具有对应于3D地震几何结构的弯曲线几何结构，但是正在使用基于2D的反演方法。这部分地由来自走时反演的3D到2D坐标投影方法来处理。结果表明，这些反射主要是由于低速区，与它们在充满水的断裂带产生一致。
Seismic full waveform inversion (waveform tomography) is a method to reconstruct the underground velocity field in high resolution using seismic data. The method was first introduced during the 1980’s and became computationally feasible during the late 1990’s when the method was implemented in the frequency domain. This work presents three case studies and one synthetic benchmark of full waveform inversion applications. Two of the case studies are focused on time-lapse cross-well and 2D reflection seismic data sets acquired at the Ketzin CO2 geological storage site. These studies are parts of the CO2SINK and CO2MAN projects. The results show that waveform tomography is more effective than traveltime tomography for the CO2 injection monitoring at the Ketzin site for the cross-well geometry. For the surface data sets we find it is difficult to recover the true value of the velocity anomaly due to the injection using the waveform inversion method, but it is possible to qualitatively locate the distribution of the injected CO2. The results agree well with expectations based upon conventional 2D CDP processing methods and more extensive 3D CDP processing methods in the area. A further investigation was done to study the feasibility and efficiency of seismic full waveform inversion for time-lapse monitoring of onshore CO2 geological storage sites using a reflection seismic geometry with synthetic data sets. The results show that waveform inversion may be a good complement to standard CDP processing when monitoring CO2 injection. The choice of method and strategy for waveform inversion is quite dependent on the goals of the time-lapse monitoring of the CO2 injection. The last case study is an application of the full waveform inversion method to two crooked profiles at the Forsmark site in eastern central Sweden. The main goal of this study was to help determine if the observed reflections are mainly due to fluid filled fracture zones or mafic sills. One main difficulty here is that the profiles have a crooked line geometry which corresponds to 3D seismic geometry, but a 2D based inversion method is being used. This is partly handled by a 3D to 2D coordinate projection method from traveltime inversion. The results show that these reflections are primarily due to zones of lower velocity, consistent with them being generated at water filled fracture zones.