Seismic Swell Effect Correction Using GVF-Based Guideline

Abstract

Swells in marine seismic data disrupt the continuity of the reflection events and make interpretation difficult. The swell effect removal process consists of sea-bottom detection and correction, which removes the swell effect by shifting the detected sea-bottom signal to the known or estimated seafloor location. The quality of correction depends on the accuracy of the sea-bottom detection. Since general sea-bottom signal detection techniques have been applied directly after pre-processing, many mispick scenarios exist due to the characteristics of the data, and additional processes are needed. This study proposes a method for accurately detecting sea-bottom reflection signals using the guideline. The errors are caused by mistaking other reflection events as sea-bottom signals. The guideline can improve detection accuracy by providing rough event times of sea-bottom reflection. The guideline was extracted from the gradient vector flow (GVF) technique, a segmentation method in image processing. In the GVF data, the seafloor signals are smoothed, and the energy is focused on the sea bottom. The threshold method detected sea-bottom signals in the range after the guideline. The detected signals were shifted to estimated seafloor locations to attenuate the swell effect. The GVF-based guideline (GVF-GL) method was applied to field data acquired by the airgun and chirp sources with different frequencies. The sea-bottom location was successfully detected, and the continuity of the sea-bottom and subsurface signals in the section was improved.