While the interpretation of seismic reflection imagery is powerful and well established for evaluating subsurface structures it is never perfectly accurate. Structural validation techniques are widely used to geometrically test geological interpretations of seismic reflection data. Commonly these techniques are performed on depth sections converted from seismic time-based data using velocity models. Velocity model choices in seismic depth conversion have an impact on the final depth image and hence the structural geometry of interpretations. The impact of these choices in depth conversion on structural validation is rarely examined. Here we explore how multiple versions of a depth section, converted using different velocity models, influence the performance of structural validations for a fold-thrust structure from the deep water Niger Delta. The example illustrates that a range of kinematic models can validate the depth-converted profiles, regardless of the depth conversion choice and are thus poor diagnostic tools. Area-depth-strain (ADS) analysis can constrain the choice both of a kinematic model and the depth conversion, provided the seismic data allow the detachment level and excess areas to be recognised. Incorporation of ADS analysis within an interpretation-depth conversion workflow helps reduce assigned uncertainty in depth conversion, the seismic interpretation, and in the implicit geological model.
Bibliographical noteThis study is based on PhD research project funded by INPEX CORPORATION at University of Aberdeen. Seismic images for this study were taken from the Higgins et al. (2009), through the courtesy of CGG (formerly CGG Veritas). Further examples are available through the Virtual Seismic Atlas (www.seismicatlas.org). Restoration and forward modelling and measurements for the area-depth-strain analysis were performed in Move 2016.1 by Midland Valley made available through academic partnership. Trishear inverse modelling was programmed referring to MATLAB scripts publicized on Allmendinger et al. (2012, chapter 11) and Nester Cardozo's website (http://www.ux.uis.no/∼nestor/work/programs.html) and implemented in MATLAB 2015b. Finally we thank Nester Cardozo and Richard Groshong for valuable comments that significantly improved this contribution.
- structural validation
- seismic interpretation
- depth conversion
- fold-thrust structures