Forensic mapping of seismic velocity heterogeneity in a CO2 layer at the Sleipner CO2 storage operation, North Sea, using time-lapse seismics
Forensic mapping of seismic velocity heterogeneity in a CO2 layer at the Sleipner CO2 storage operation, North Sea, using time-lapse seismics
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DOI：
10.1016/j.ijggc.2019.102793
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发表时间：
2019-11-01
影响因子：
3.9
通讯作者：
Falcon-Suarez, I
中科院分区：
文献类型：
--
作者：
Chadwick, R. A.;Williams, G. A.;Falcon-Suarez, I
从Sleipner和Gudrun油田生产的天然气中分离出来的二氧化碳正在注入乌齐拉沙，目前储存了大约1800万吨。已经部署了延时三维地震仪来监测二氧化碳羽流的发展。2010年的地震勘探首次以3D方式将最顶层的CO2层分解为顶部和底部的不同反射。地震速度是诊断的CO2层的属性和法医解释的方法是通过确定空间速度变化的最高CO2层。通过将绝对层厚度（通过从储层顶部的地形起伏减去构造的平坦CO2 -水接触面）等同于层顶部和底部反射的时间分离，并对小波干扰效应进行适当校正，获得速度。层速度在平均速度为1371 +/- 122 ms（-1）的北方区域和平均速度更高的1638 +/- 103 ms（-1）的中心区域之间显示出系统的和稳健的空间变化。最近的流体流动模拟的最高CO2层已经表明，将高渗透率的通道中的模型储层显着提高了历史匹配。该高渗透性通道与北方区域绘制的低地震速度非常接近，中心区域的较高层速度被解释为泥质较多、渗透性较低的漫滩沉积物。因此，新的速度分析提供了独立的支持，包括确定性渗透率的非均质性预测流体流动模型的Sleipner。
CO2 separated from natural gas produced at the Sleipner and Gudrun fields is being injected into the Utsira Sand, with around 18 million tons currently stored. Time-lapse 3D seismics have been deployed to monitor development of the CO2 plume. The 2010 seismic survey resolved, for the first time in 3D, the topmost CO2 layer into distinct reflections from its top and base. Seismic velocity is diagnostic of CO2 layer properties and a forensic interpretative approach is adopted to determine spatial velocity variation in the topmost CO2 layer. Velocity is obtained by equating absolute layer thickness, derived by subtracting a constructed flat CO2 - water contact from the topographical relief of the reservoir top, to the temporal separation of the layer top and base reflections, with appropriate correction for wavelet interference effects. Layer velocities show a systematic and robust spatial variation between a northern area with a mean velocity of 1371 +/- 122 ms(-1) and a central area with a much higher mean velocity of 1638 +/- 103 ms(-1). Recent fluid flow simulations of the topmost CO2 layer have shown that incorporating a high permeability channel in the model reservoir significantly improves the history-match. This high permeability channel corresponds remarkably closely to the low seismic velocities mapped in the northern area, with higher layer velocities of the central area interpreted as more argillaceous, less permeable overbank deposits. The new velocity analysis therefore provides independent support for including deterministic permeability heterogeneity in predictive fluid flow modelling of Sleipner.