Challenges of 3-D Interpretation and Seismic Reservoir Characterization in the Depth Domain
Le Stunff, Yves, Total, Pau, France
Seismic interpreters are often reluctant to work directly in the depth domain, although benefits are numerous. These include a direct link with geo-models for the transfer of horizons, faults or attributes and improved communication with geologists, reservoir engineers and drillers.
The main concern is the difficulty to solve simultaneously the problem of time-to-depth conversion and the problem of imaging, i.e. the difficulty to find a 3D velocity model that satisfies simultaneously well data and seismic velocities. 3D Seismic Tomography algorithms are now able to mix well and seismic velocity information (usually through the introduction of anisotropy). However further local refinements of the model are usually done since depth interpreters require a highly accurate velocity model. Thus one of the challenges is to be able to refine and update quickly 3D velocity models and 3D seismic depth cubes without going into costly additional depth migration steps.
Seismic reservoir characterization in the depth domain is also in its infancy. Only Preserved Amplitude Pre-Stack Depth Migration algorithms are able to produce, in theory, seismic information that can be directly used for reservoir characterization. This technique remains however costly and other solutions such as migration of seismic attributes (from time migrated data) can be a good alternative. Examples of seismic characterization on Preserved Amplitude Depth Migration and of migration of seismic attributes will be presented. The development of these techniques will have of course a large impact on future 4D studies where working in depth is a key element for success.