Estimation of the variability of sand deposits in chosen communities in parts of Niger delta, Southern-Nigeria using geophysical techniques

Abstract

Fine and coarse typical sand are among the most vital raw materials in building construction. A lot of drilling has been done without appropriate subsurface information resulting to a waste of resources and time. Geophysical methods give information on subsurface lithologies to locate areas with huge success. Thus, a geophysical investigation of subsurface deposits was carried out in this research to ascertain the quantity of fine/Coarse sand or areas with viable fine/Coarse sand utilizing Schlumberger configuration, Dipole–Dipole (2D) and well logging in parts of Okpe and Ughelli North LGA of Delta State, Nigeria, before extraction (dredging) for the benefit of exploitation and development. This was done by assessing the geo-electric formation of fine/coarse sand in the studied areas concerning their depths and thicknesses. Seven Vertical Electrical Sounding (VES) were obtained with the application of Schlumberger array, seven 2D and three well logging to estimate the viability of sand deposits in the study areas. These techniques have the efficacy of detecting near-bed formation with vital resolution. The data obtained from the field were illustrated by partial curve matching coupled with computer iteration using the WIN RESIST and Dipro Software to obtain sounding curves which revealed four to six layers. The layers consist of topsoil, lateritic clay and clayey sand, fine sand deposit, medium to coarse grain sand and coarse sand. For Agbarho, thicknesses of fine/coarse sand in the VES stations ranges from 18.0 to 55.6 m with resistivity varying from 223.7 to 572.9 Ωm, Osubi Fine/Coarse sand thickness ranges from 13.5 to 59.9 m with resistivity values within 211.9–891.0 Ωm and Oha town locations have fine/coarse sand thickness varied from 46.6 to 83.7 m with resistivity interval computed between 145.9 Ω-m and 466.4 Ω-m. Thus, the best VES stations that are more viable for sand mining are VES 1, 5 and 7 which contain relatively huge viable sand deposits in the study areas to a depth above 80 m.