Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Abstract:
This paper describes an attempt at geo-electric characterization of the beach ridge utilizing sub-soil resistivity measurements on the onshore pipeline route at Escravos terminal in Western Niger Delta, Nigeria. Electrical resistivity survey methods comprising Wenner Electrode Configuration for resistivity profiling along the pipeline routes and Schlumberger array for vertical depth sounding for groundbed locations were adopted in the study. Pre-determined current electrode spreads were adopted at each sounding location. Results show that the stratigraphy of the superficial layers indicates a reasonable degree of uniformity from BH2 to BH12 with a top soft organic silty clay underlain by sandy clay that grades into loose to medium fine grained sand towards 10m depth. Water table is close to the ground surface and the sections of the pipeline route are periodically submerged by seasonal and sometimes tidal floods. The pipeline route resistivity profiling indicates a corrosive soil in the tank farm area (with soil resistivity value ranging between a 10 - 50?m) and severely corrosive soil in the swamp to beach area (with soil resistivity value of about or less than 10?m). The range of resistivity values indicates high soil aggressiveness. The strong tidal reversal that inundates the swamp area increases soil water saturation and soil salinity thus increasing soil conductivity in the area. The resistivity values of the sub-surface layer in the choice groundbed location area suggest a shallow groundbed probably within 15m. It is suggested that the economic analysis and the ultimate recommendation by the "corrosion expert" should govern the optimum application of cathodic protection and protective coating for the intended buried structures and pipelines. Similarly, details of other existing cathodic protection (CP) system for structures lying within the periphery of the pipeline route should be examined to avoid interference with the intended CP system. The study clearly evaluated the geo-electric properties of the subsoil at the sudy area providing not only a baseline knowledge of the geo-electric properties of the sub-units but also the necessary design data for effective cathodic protection and choice of groundbed locations for the anode wells.

Keywords: geo-electrical, resistivity profiling, corrosivity, cathodic protection, beach ridge, Niger Delta.

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