Geophysical Investigation of the Causes of Borehole Failure in the Crystaline Basement Complex: A Case Study of Kaura Area of Kaduna State, Nigeria

Abstract

Vertical Electrical Soundings (VES) using Schlumberger array were carried out at different points along five (5) profiles. This research investigates the causes of massive  borehole failure at Kaura  area of Kaduna state using the resistivity tomography techniques. Terrameter SAS300 is the instruments used to acquire the data. A total of 19  boreholes  are  functioning,  while  31  boreholes  are  non-functioning  within  the  area.  The  investigation  has portrayed the possible factors which are most probably causative to borehole failures in the area which involves the  design  and  construction,  groundwater  potential/hydrogeological  factors  and  operational  and  maintenance factors. It was found out  that it  is possible  for one factor to lead to the  other.  For  example, a  borehole poorly designed, constructed and completed could result in sand/clay pumping and eventually affect the rubber seals in the  hand  pumps  or  the  impellers  in  the  case  of  submersible  pumps.  The  boreholes  tap  the  weathered  and fractured basement aquifers of the area with yields ranging from 2 litre/min to 20 litre/min. However, yields from Sandy soil aquifers were found to be extensive. The survey shows that boreholes with initial recorded yield less than 10 litre/min have failed over time. The survey reveals that the areas  where wells and boreholes are drilled through  sandy soil  and  fracture  zones  have  sustainable aquifers  for  groundwater  exploitation,  while  boreholes that are constructed through clayey formation usually fail.

Keywords: Resistivity1, Kaura2, Borehole failure