Evaluating Linear Moveout Effectiveness in Detecting 3-D Seismic Survey Geometry Errors in Chad Basin, Nigeria

Abstract

Accurate geometry is critical for the integrity of three-dimensional seismic surveys for hydrocarbons, particularly in structurally complex basins such as the Chad Basin, Nigeria. This study evaluates the effectiveness of linear moveout (LMO) analysis as a diagnostic tool for detecting and correcting geometry errors during 3-D seismic survey for hydrocarbon in the Chad Basin of Nigeria. Pre-stack seismic gathers from a recent survey were subjected to systematic LMO workflow analysis that included resampling of raw field data at 4ms sample rate, screen quality control followed by database geometry assignment to field data trace headers. LMO corrections was then applied using velocities representative of the near-surface and shallow subsurface formations. The corrected gathers were examined for residual linear trends, abnormal event alignments, and discontinuities indicative of geometry inconsistencies.  Diagnosis showed that properly positioned source-receiver configurations produced coherent seismic events that flattened consistently after LMO corrections. In contrast, gathers affected by geometry errors displayed persistent linear trends, events misalignments, and irregular offset-dependent distortions even after LMO application. These observed anomalies clustered along acquisition lines segments of flooded terrain where flood level covered the receiver stations, suggesting localized position inaccuracies due to wrong receiver line deployment. The study concludes that Linear Moveout analysis is a reliable approach for early detection of 3-D seismic geometry errors and that integrating it into quality control workflow reduces geometry errors significantly prior to migration thus improving both stacking coherence and subsurface imaging fidelity.