Post drilling investigation for prolific groundwater aquifer using geoelectric logging at Nigeria LNG base, Port Harcourt

Post-drilling investigation for prolific groundwater aquifer was conducted in a well at the Nigeria LNG Base, Port Harcourt using geoelectric logging. Resistivity (Short Normal and Long Normal) and Self-Potential (SP) logs were employed. Two zones (A and B) were tested to determine the porosity (ɸ), permeability (k) and the total dissolved solids (TDS) in the aquifer. Results show that the inferred lithology in the borehole consists of sand, clayey-sand and clay materials. They also indicate that test zone A (110-140 m), though permeable, has high membrane potential which is higher than the liquid-junction potential resulting from clay intercalation thereby reducing its viability as a production zone. Zone B is found to be prolific with porosity and permeability values of 18% and 131.31 mD respectively at depth range of 140 to 180 m. The total dissolved solid (TDS) derived from electrical conductivity (EC) value of 6250 μmhoscm-1 is 4000 mg/litre for this zone. The high TDS value observed within this prolific groundwater zone in the well may be as a result of effluent discharge by industries around the area or saline water intrusion due to its proximity to the Bonny River. The 4000 mg/litre falls outside the World Health Organization’s acceptable limit palatability for drinking water and may have the negative effects of excessive scaling in water pipes, water heaters, boilers, and domestic appliances such as kettles and steam irons which may reduce their service span. Effective water treatment is therefore recommended. Key words: Self-potential, resistivity, electrical conductivity, geoelectric, aquifer, total dissolved solids.