Study into the Weathering Layer Using Deep Uphole of Seismic Refraction in Enaga Area.

(Concession 72, Sirte basin, Libya)

Abstract

The study aims to determine the characteristics of the weathering layer and to determine the appropriate replacement velocity for static corrections to address the challenges posed by the weathering layer and improve the results of the static correction for the three-dimensional seismic data conducted in 1996 for the study area. Deep uphole survey conducted in 2005 for seven deep wells up to 600 meters deep in the En Naga area (Concession 72, Sirte Basin, Libya). The results revealed significant heterogeneity and horizontal variation in seismic wave velocity throughout the weathering layer, with values ​​ranging from 700 to 2,200 m/s and a thickness ranging from 475 to 560 meters. The sub-weathering layer was identified as the most homogeneous in terms of seismic wave velocity, with seismic velocities ranging from 3,000 to 3,800 m/s. The study successfully standardized the replacement velocity across the entire study area, overcoming the limitations of previous studies that proposed multiple velocities. Although the data provided a general understanding of subsurface conditions, the limited number and spacing of wells highlighted the need for further data collection to improve static corrections and enhance seismic data interpretation. The study provided a solid foundation for improving the quality of seismic sections and enhancing oil exploration conditions in the region.