Improvements in seismic imaging and migration-velocity model building
Appears in the following Collection
- Institutt for geofag 
AbstractSeismic imaging methods have been widely used in the petroleum industry for hydrocarbon exploration and reservoir monitoring. The principle of seismic imaging methods is employing elastic waves generated by seismic source to obtain images of the subsurface. In seismic acquistion, the emitted seismic waves propagate down into the Earth, and are reflected and refracted at each lithostratigraphic boundary. Those reflected waves are recorded by sensors near the surface within a defined time period, and are subsequently processed in order to image the subsurface structures, predict the types of rocks encountered and determine the presence of hydrocarbons (oil and gas). With the progress of exploration and production, the petroleum industry has moved into exploring fields that have ever more complex geological structures, such as the salt deposits in the Nordkapp Basin in the Norwegian Barents Sea and pre-salt discoveries in the Santos Basin in Brazil. The conventional seismic processing and imaging methods have challenges with the quality of resolution, signal-to-noise ratio (SNR) or accuracy of the image in such geological scenarios. This thesis focuses on the development of improved high-resolution seismic imaging techniques, in combination with the iterative, 3D velocity model-building approach, in order to address velocity modelling and depth imaging in complex geological scenarios. As a result of this work, three main contributions have been made to improved seismic imaging: (1) A fast and robust seismic wavefront, or Common-Reflection-Surface (CRS), attributes estimation method in CRS stacking to provide improved SNR in seismic images of complex subsurface geological structures. (2) An improved Fourier mixed-domain prestack depth migration technique to image vertical transversely-isotropic (VTI) media with large lateral contrasts and complex structures. (3) A new time-migration velocity estimation algorithm using nonlinear mapping of seismic wavefront attributes based on the kinematic time migration and demigration schemes.
List of papers
|Paper I: Fast and robust common-reflection-surface parameter estimation. Anders U. Waldeland, Hao Zhao, Jorge H. Faccipieri, Anne H. Schistad Solberg, and Leiv-J. Gelius. Geophysics VOL.83 NO.1 (2018), O1-O13. DOI: 10.1190/GEO2017-0113.1. The article is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1190/GEO2017-0113.1|
|Paper II: 3D Prestack Fourier Mixed-Domain (FMD) depth migration for VTI media with large lateral contrasts. Hao Zhao, Leiv-J. Gelius, Martin Tygel, Espen Harris Nilsen, and Andreas Kjelsrud Evensen. Journal of Applied Geophysics VOL.168 (2019), 118-127. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.jappgeo.2019.06.009|
|Paper III: Time-migration velocity estimation using Fréchet derivatives based on nonlinear kinematic migration/demigration solvers. Hao Zhao, Anders U. Waldeland, Dany Rueda Serrano, Martin Tygel, and Einar Iversen. Studia Geophysica et Geodaetica (2020). DOI: 10.1007/s11200-019-1172-0. The paper is included in the thesis. The publisjed article is available at: https://doi.org/10.1007/s11200-019-1172-0|