Analytical Investigation of Hydraulic Fracturing Risk to Groundwater in the Bida Basin, Niger State

Proposals for hydrocarbon extraction from the Bida Basin in Niger State raise questions about groundwater contamination risk from hydraulic fracturing operations in proximity to productive aquifer systems on which North Central Nigerian communities depend. This study provides an analytical investigation of hydraulic fracturing risk to groundwater resources in the Bida Basin. A risk assessment methodology integrating groundwater vulnerability mapping, contaminant fate and transport modelling, and uncertainty analysis was adopted. Geological cross-sections were constructed from available borehole logs and seismic data to characterise the vertical separation between target hydrocarbon formations and shallow potable aquifers. Groundwater vulnerability was assessed using the DRASTIC index for the shallow aquifer system. Contaminant transport modelling using MODFLOW and MT3DMS evaluated hypothetical leak scenarios. Interviews with 20 hydrogeologists and environmental engineers provided expert opinion data. Results indicate that the shallow alluvial aquifers in the basin are separated from hydrocarbon target formations by 600 to 1,200 m of predominantly low-permeability clay-rich strata, providing a significant geological barrier to vertical contaminant migration under intact casing conditions. DRASTIC vulnerability is high in unconfined river valley aquifers adjacent to potential drilling sites. The study concludes that while geological separation provides a degree of natural protection, near-surface casing integrity is the critical risk factor, and recommends mandatory baseline groundwater quality monitoring before any exploratory drilling activity.

Keywords: hydraulic fracturing, groundwater contamination risk, Bida Basin, Niger State, DRASTIC vulnerability