Application of Geophysical Methods in Pipeline Integrity Assessment for NNPC Trunk Lines in the Niger Delta, South South Nigeria

Pipeline integrity failures in the Niger Delta remain a significant operational and environmental challenge for the Nigerian National Petroleum Corporation, with corrosion, third-party interference, and ground movement implicated as primary causes. This study evaluates the application of geophysical techniques, specifically electrical resistivity mapping and close-interval potential surveys, for systematic assessment of pipeline integrity along 35 kilometres of NNPC trunk lines traversing swampy and upland terrain in Delta State. The close-interval potential survey was conducted at 1-metre intervals along accessible pipeline sections, generating polarisation potential profiles that identify areas of cathodic protection deficiency. Complementary electrical resistivity profiling perpendicular to the pipeline route at 500-metre intervals provides soil corrosivity classification based on measured ground resistivity values. Potential readings below negative 850 millivolts (copper-copper sulphate) are used as the criterion for adequate cathodic protection, revealing 12 deficiency zones distributed non-uniformly along the assessed route, predominantly in waterlogged clay-rich soil sections. Soil resistivity measurements indicate severe corrosivity (less than 10 ohm-metres) in 8 of the 12 deficiency zones, confirming the geotechnical environment as a compounding factor. The study proposes a risk ranking framework for prioritising pipe section rehabilitation and enhanced cathodic protection installation. Findings contribute to a geophysics-integrated pipeline integrity management protocol aligned with NUPRC corrosion prevention requirements. Keywords: pipeline integrity, cathodic protection, corrosion, Niger Delta, geophysics