Reflection Enhancement Processing in Ultra-Shallow Seismic Data

Abstract

The lack of standard procedure for processing shallow reflection seismic data is an impediment to the use of reflection seismic data for near surface applications. The wave field of ultra-shallow reflection data is often complicated by low frequency high amplitude events in the same time window with primary reflections. The standard method for processing exploration-scale seismic data proved unsatisfactory for ultra-shallow reflection seismic data: scaling down the acquisition geometry is inadequate because the frequency bandwidth of the data recorded does not scale up in the same proportion. In this study, data-driven workflow of specialised techniques is used to preserve the low-amplitude energies reflected by shallow geological layers. Surgical top and end muting; cone and polygonal muting;  spectral-filtering techniques and careful validation of coherent events, by synthetic modelling, were combined to degrade noise and other non-reflection events. A combination of constant velocity gather, Semblance Plot, and Constant Velocity Stack techniques was applied to obtain the optimum move-out velocity. Applied to an ultrashallow seismic data from Southeast Spain, the workflow improved the signal-to-noise ratio of processed data. The CDP–stacked image constructed for the survey reveals some shallow vertical faults suspected to be associating with the main Carbonera Faults. These faults are comparable to faults projections constructed from a field based geological mapping undertaken many years before the seismic survey.