Anisotropic 3D full-waveform inversion
Anisotropic 3D full-waveform inversion
复制标题
DOI：
10.1190/geo2012-0338.1
复制
发表时间：
2013-03-01
期刊：
影响因子：
3.3
通讯作者：
Bertrand, Alexandre
中科院分区：
文献类型：
--
作者：
Warner, Michael;Ratcliffe, Andrew;Bertrand, Alexandre
我们开发并实现了一种鲁棒且实用的各向异性三维声学全波形反演（FWI）方案。我们在现场数据集上演示了该方案，并将其应用于北海Tommeliten Alpha油田的4C海底调查。该浅水数据集提供了良好的方位角覆盖，偏移量为7公里，最大偏移量约为11公里。储层位于高速反形式白垩剖面的顶部，被约3000米的碎屑覆盖，其中的低速气体云产生了地震遮挡区。我们只反演了水听器数据，并保留了现场数据中的自由面倍数和鬼影。我们在6个狭窄的频带中反转，范围在3到6.5 Hz。在每次迭代中，我们只选择源的一个子集，在每次迭代中使用不同的子集；这种策略比每次迭代都反转所有数据更有效。我们的起始速度模型是使用包括各向异性反射层析成像在内的标准PSDM模型构建获得的，其中包含高达20%的epsilon值。最终的FWI速度模型显示了一个浅层高速通道网络，与反射数据中的相似特征相匹配。在剖面的更深处，FWI速度模型显示了一个与气体云相关的更清晰、更强烈的低速区，其中低速指与反射数据中可见的充满气体的断层位置相匹配。与初始模型相比，所得到的速度模型能够更好地与测井曲线匹配，并且能够更好地平坦化普通图像集。利用FWI速度模型进行逆时偏移，可以显著提升偏移图像，简化油藏剖面的平面。我们所使用的工作流、反演策略和算法在反演广泛的类似数据集方面具有广泛的应用。
We have developed and implemented a robust and practical scheme for anisotropic 3D acoustic full-waveform inversion (FWI). We demonstrate this scheme on a field data set, applying it to a 4C ocean-bottom survey over the Tommeliten Alpha field in the North Sea. This shallow-water data set provides good azimuthal coverage to offsets of 7 km, with reduced coverage to a maximum offset of about 11 km. The reservoir lies at the crest of a high-velocity antiformal chalk section, overlain by about 3000 m of clastics within which a low-velocity gas cloud produces a seismic obscured area. We inverted only the hydrophone data, and we retained free-surface multiples and ghosts within the field data. We invert in six narrow frequency bands, in the range 3 to 6.5 Hz. At each iteration, we selected only a subset of sources, using a different subset at each iteration; this strategy is more efficient than inverting all the data every iteration. Our starting velocity model was obtained using standard PSDM model building including anisotropic reflection tomography, and contained epsilon values as high as 20%. The final FWI velocity model shows a network of shallow high-velocity channels that match similar features in the reflection data. Deeper in the section, the FWI velocity model reveals a sharper and more-intense low-velocity region associated with the gas cloud in which low-velocity fingers match the location of gas-filled faults visible in the reflection data. The resulting velocity model provides a better match to well logs, and better flattens common-image gathers, than does the starting model. Reverse-time migration, using the FWI velocity model, provides significant uplift to the migrated image, simplifying the planform of the reservoir section at depth. The workflows, inversion strategy, and algorithms that we have used have broad application to invert a wide-range of analogous data sets.