Uphole seismic refraction survey for determination of Near subsurface velocities in Eziobodo and its Environs Imo state southeastern Nigeria

Abstract

An uphole survey was carried out in Eziobodo and its environs which are located within the Niger Delta sedimentary Basin. The aim of the survey was to investigate the thickness of the weathering layer (Low Velocity Layer, LVL) and find the velocity trend in the area. A total of 21 upholes were shot. The arrival times (first breaks) of the shots were picked and plotted against the distance. The velocities and the thickness of the weathering layer were computed from the plots. The results show a variation in the thickness of the LVL ranging from 10.4 m to 20.72 m averaging 16.31 m. The velocity of the weathered layer ranges from 472.34 ms^–1 to 796.86 ms^–1 with an average of 623.40 ms^–1. The velocity of the consolidated layer ranges from 1500.62 ms^–1 to 1918.22 ms^–1 with an average of 1743.72 ms^–1. Knowledge of the thickness and velocity of the near surface layers (LVL) could be useful in the oil and gas as well as groundwater explorations. It could also be useful to groups interested in civil or geotechnical engineering.

Keywords: Uphole, Seismic, Refraction