Groundwater prospects in the basement complex rocks of southwestern Nigeria

Abstract

The results of drilling more than 40 wells for several clients in the Basement Complex rocks of southwestern Nigeria since 1981 by Geostruct Company have shown that wells can be successfully located in Basement Complex areas without necessarily relying on expensive, preliminary geophysical studies. Out of 45 wells drilled, only three proved abortive, representing a success rate of 93 per cent. This success rate is significant when it is realised that the locations of all the wells were restricted to sites specified by the various clients. Furthermore, most of the wells were drilled without reliance on preliminary geophysical investigations. It has also been observed that wells located in pegmatitic areas have better yield than wells located in finer grained equivalents.

The conclusion from observation and experience is that local geological conditions, some of which are not readily amenable to geophysical investigations, play a critical role in the yield of wells located in the Basement Complex areas of southwestern Nigeria. Suggestions, based on field experience, as to the proper roles of geology and geophysics respectively, in the exploration for groundwater in Basement Complex areas are thus made.