Compared to time migration, depth imaging should yield simpler structure, higher spatial and vertical resolution, and a more stable phase response. It is also the appropriate input for inversion and other attributes that estimate reservoir properties and mitigate risk. However, the interpreter must actively guide the depth-imaging process to ensure a reasonable, geologic result. This talk reviews the planning and QC of depth imaging in a manner that establishes an appropriate dialogue between the interpreter and the processor.
When choosing a company (or companies) for imaging, it is critical they provide the level of technology suitable for the interpretive goals. As such, the (bidding) dialogue should include:
-Defining deliverables in terms of interpretive goals
-Establishing a minimalist approach to initial time processing
-Choosing appropriate migration and tomography algorithm(s)
-Discussing and establishing the target (final) velocity resolution
-Ensuring that deliverables are compatible with forming 3rd-party attributes
When beginning the imaging process, a critical step is the formation of the initial velocity model. Figure 1 is an example of an acceptable, smoothly-varying model. In general, the addition of detail early in velocity-model formation is to be avoided.