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Laboratory modelling of geoelectric response of a leaking underground petroleum storage tank in sand formation


O Afolabi
MO Olorunfemi

Abstract

Laboratory modelling of a simulated subsurface hydrocarbon impacted sand was carried out using a model tank. A crude oil filled metallic cylindrical tank (simulating a typical crude / refined hydrocarbon storage tank) was buried in the sand and pre-impact resistivity measurements with various electrode arrays (Wenner, dipole-dipole and gradient) were carried out along seven traverses, three of which traversed the buried cylindrical tank.


A subsurface impact via crude oil leakages from the sides of the cylinder was initiated and post-impact resistivity measurements were made with same electrode arrays and along the same traverses. The study was aimed at generating characteristic geoelectric signatures or patterns for the pre-impact and post-impact hydrocarbon-impacted sand.


Results from the resistivity profiles, maps and pseudosections as well as the inversion of the dipole-dipole data indicate diagnostic relatively high resistivity anomalies over the hydrocarbon-impacted zone.


Although the three electrode arrays resolved the lateral extent of the impacted zone, a combined horizontal/vertical profiling involving dipole-dipole array proved more useful in determining the lateral and vertical extent, i.e., the geometry of the contaminated zone. It also enabled an approximate estimation of the volume of leaked hydrocarbon. Apart from resolving the hydrocarbon-impacted zone, the method also identified the source of impact.


KEY WORDS: subsurface, leakage, resistivity, anomaly.


Global Journal of Geological Sciences Vol.2(2) 2004: 207-220

Journal Identifiers


eISSN: 2992-4502
print ISSN: 1596-6798