On the use of computerized tomography scan analysis to determine the genesis of very high resolution seismic reflection facies

摘要

Computerized tomography scanner (CT scanner) is a powerful tool that can reveal millimeter-scale stratigraphy from cores. The coupling of very high resolution (VHR) seismic data with CT scan data represents a new approach to determine with more confidence the genesis of seismic facies. However, prior to the application of such a method, a clear understanding of the relationship between these two types of data (e.g., physical parameters in common) is necessary. The application of CT scan analysis along with VHR seismic data showed that seismic and CT scan signals respond to different physical properties of the sediments. Results suggest that similar seismic facies may correspond to different CT scan facies and, conversely, that different CT scan facies may have the same acoustic response. Sedimentary structures observed on the CT scan imagery suggest that a seismic response should be linked to a synthesis of lithological variations instead of a single and unique lithology change/contrast. Furthermore, this study points toward the fact that the geometry of the reflections does not always correspond to the geometry of sedimentary structures but rather to the anisotropy of the physical properties of the deposit. Consequently, to give a genetic connotation to the internal reflection pattern of a seismic facies can be misleading in some cases. Finally, the fine-scale sedimentological analysis based on very high resolution CT scan data is useful to determine very fine seismic analogs and thus to better explain the seismic expression of a deposit.