The use of uphole method in the mapping of the thickness and velocity of the low velocity layer in parts of Eastern Niger Delta, Nigeria

Abstract

Traveltimes from uphole survey operation carried out in 50 locations in the south-east Niger Delta were picked and analyzed to determine the area weathering structure using the time-intercept method. Analysis of the results shows that the thickness of the low velocity layer in the region varies from 2.6 to 13.3 m, with an average of 8.2 m. The weathering velocity ranges from 214.3 to 905.1 m/s; with an average value of 487.9 m/s. The refractor beneath it has velocities ranging from 1125.0 to 2069.1 m/s; with an average value of 1604.2 m/s. Hence it is established that the thickness and velocity of the weathering layer can vary from one shot point to another in the area of study. The resulting information is essential in oil and groundwater exploration in the area, especially in estimating static corrections and time delays during the processing of seismic reflections. Also the information could be useful in civil engineering works in the determination of the capacity of the foundation rock.

Keywords: Uphole method, Traveltimes, Weathering velocity, Low velocity layer, Eastern Niger Delta.