Sleipner is the world’s longest-running CO₂ storage project. Since injection commenced in 1996 almost 1 million tonnes per year have been injected with more than 16 million tonnes successfully stored by 2016. A comprehensive programme of time-lapse 3D seismic monitoring has been carried out, providing unrivalled imaging of the CO₂ plume as it has developed and migrated in the storage reservoir. The plume has a tiered structure comprising a number of thin layers of CO₂ of the order of a few metres thick. Determination of accurate layer morphology is key to understanding details of fluid flow processes in the plume which is necessary to demonstrate future storage security. Migration of the topmost layer of CO₂, trapped directly beneath the reservoir topseal, determines the longer-term storage performance at Sleipner and here we focus on mapping its travel-time (temporal) thickness. Our primary approach is to use spectral analysis to determine tuning frequencies across the layer and from these to derive temporal thickness. These range from zero at the layer edges to around 16 ms in the central parts of the layer and correlate closely with the base topseal topography. Uniquely, results are then compared with those from other published approaches including amplitude analysis, temporal shifts and direct measurement of temporal spacing on the latest high-resolution seismic data. It is clear that the spectral methods provide robust determination of temporal thickness well below the tuning thickness, and, taken in suitable combination with the various other methods, can provide reliable determination of temporal thickness across the range from close to zero to well above the tuning thickness where explicit layer resolution is obtained. Application of an appropriate layer velocity allows true layer thicknesses to be determined and layer volumetrics to be estimated.

Sleipner是世界上运行时间最长的CO ₂封存项目。自从1996年开始注入以来，每年已注入近100万吨，到2016年已成功存储了超过1600万吨。已经进行了延时3D地震监测的综合计划，可提供无与伦比的CO ₂羽流成像。已经在储层中发展并迁移了。羽流具有分层结构，该分层结构包括许多厚度为几米的薄薄的CO ₂层。确定准确的层形态是了解羽流中流体流动过程细节的关键，这对于证明未来的存储安全性是必不可少的。迁移最顶层的CO ₂困在储层顶部密封之下，决定了S​​leipner的长期储藏性能，在这里我们着重于绘制其行进时间（时间）厚度。我们的主要方法是使用频谱分析来确定整个层的调谐频率，并从中得出时间厚度。这些范围从层边缘的零到层中心部分的16 ms左右，并且与基础顶部密封形貌密切相关。然后，将结果独特地与其他已发布方法（包括幅度分析，时间偏移和直接测量最新高分辨率地震数据的时间间隔）的结果进行比较。显然，光谱方法可以可靠地确定远低于调谐厚度的时间厚度，并且 适当地结合各种其他方法进行的测量，可以在从接近零到调整厚度的范围内可靠地确定时间厚度，该范围从获得明确层分辨率的调整厚度开始。施加适当的层速度允许确定真实的层厚度并估计层体积。