SITE CHARACTERIZATION USING UPHOLE SEISMIC REFRACTION TECHNIQUE IN PINDIGA, GOMBE IN NIGERIA

Abstract

Six uphole seismic refraction profiles were acquired in Pindiga Field, Gombe in Nigeria, using seismic uphole refraction method. The aim of the study was parameterize the site of lithology, near-surface stratigraphy, and velocity for geotechnical and velocity regimes for seismic data processing. The data was recorded using Stratavisor Model NZXP Recorders, processed and interpreted using OMNI, Petrel, Landmark, UDISYS, SeisUp, WavePack, Excel softwares. The results of the interpreted data reveal three-layer cases having dominant geologic lithologic sequences of sandstone, clay and silt, and intercalation of laterite, ironstone, coal and gravels up to a depth of 65m. The sand is an admixture of the various sizes but demarcation is based on the size as define by Wentworth scale of classification. In the First Weathered Layer, the velocity varies between 363ms-1 and 453ms-1 with an average of 391ms-1. In the Second Weathered Layer, the velocity varies between 702ms-1 and 870ms-1 with an average of 834ms-1. For the Third Weathered Layer, the velocity varies between 1012ms-1 and 2104ms-1 with an average of 1182ms-1. In the Consolidated Layer, the velocity varies between 1012ms-1 and 2104ms-1 with an average of 1182ms-1. Velocity regime varies between 1235ms-1 and 2500ms-1 with an average of 1556ms-1. First Weathered Layer, the thickness varies between 2.6m and 4.7m with an average of 3.45m. Second Weathered Layer, the thickness varies between 0.9m and 41.5m with an average of 22.75m. Third Weathered Layer, the thickness varies between 12.5m and 45.9m with an average of 26.43m. The lithology, depth and velocity results of this work can be used to characterize a site, and also be applied in the processing of seismic reflection survey data.