Print this pageWork Processes to Mitigate Interpretation Pitfalls in Complex Imaging Environments
The presence of thick evaporites, dense faulting and velocity variability in a basin creates a complex seismic imaging environment. The alignment and character of seismic reflections can be distorted in such environments and limit the ability of an interpreter to extract useful stratigraphic information from the data. In these complex imaging areas 3D visualization and mapping techniques, combined with an understanding of the reflection seismology, can assist in avoiding interpretation pitfalls and help produce viable geologic scenarios.
Diapirs, steep-sided mini-basins, rugosity at the top and/or base of the evaporite section and variable internal geometries are common characteristics of basins containing significant thicknesses of evaporites. The pre-evaporite sedimentary section is susceptible to illumination, imaging and noise issues that result from these characteristics and degrade the amplitude and alignment of reflections as well as the overall vertical and lateral resolution. The use of multi-volume visualization techniques such as co-rendering discontinuity or dip volumes with reflection seismic volumes along with multi-slice views allow the interpreter to identify imaging issues and help distinguish signal from noise in the pre-evaporite section.
Dense faulting, on a regional to sub-regional scale, can also lead to complex imaging issues. If these features are not viewed in volume space, it is possible, to incorrectly characterize them as related to stratigraphy. The application of multi-slice views which include tilted planes and traverses that match fault planes aid in the recognition of these artifacts.
The measure of velocity in the sub-evaporite sedimentary section is hindered by the loss of angle ranges in the seismic gathers. The inability to measure internal velocity variability with confidence makes the interpretation/prediction of potential reservoir and seal intervals difficult. Regional mapping and paleo-reconstructions are necessary to help generate potential reservoir and seal trends.
Understanding the issues related to migration sweep, spatially coherent noise, false structuring and velocity can help the seismic interpreter avoid potential stratigraphic interpretation pitfalls. Recognition and mitigation of these issues through the use of techniques such as multi-volume 3D visualization, modeling, reconstructions and isopach mapping can result in an interpretation that better represents the true sub-surface geology.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil