3D Errors in 2D Seismic Images: Analysis and Prediction of Errors Due to a Thrust Fault

Seismic data collected in complex land settings is often two-dimensional (2D). The data is then processed in 2D, and these 2D images are ideally representative of the subsurface beneath the profile. This may not be the case, however, if the subsurface has complicated three-dimensional (3D) structure and lateral heterogeneity, like in fold-and-thrust belt settings. In order to quantify these 3D errors in 2D seismic images, we carried out a synthetic case study using a 3D model based on the Caipipendi block in Bolivia, where a target horizon lies beneath a thrust fault. We compare results from illumination studies and 2D migrated images with predicted errors due to a single thrust fault. Illumination studies reveal that seismic energy can reflect off subsurface boundaries kilometers outside of the crosslines. The target in the crosslines consequently has migrated depth errors of tens to hundreds of meters. The thrust fault explains the majority of the errors, both in the lateral direction perpendicular to the 2D plane, and in depth. Our thrust fault error prediction equations have the potential to correct for errors in a seismic strikeline due to a cross-dipping thrust fault and can be incorporated into uncertainty analysis and risk assessment.