© 2007, INSInet Publication A Comparative Study of the Accuracy of Preliminary Interpretation Techniques in Computer-aided Vertical Electrical Sounding (Ves) Data Interpretation

Abstract

Abstract: This paper investigates the significance of the accuracy of the starting model parameters generated from conventional partial curve matching (CPCM), the asymptotes/inflection points (AIP) and the type curve-controlled guess (TCCG) techniques of Vertical Electrical Sounding (VES) preliminary interpretation. The study involves both model studies and field data analysis. A total of thirty (30) Schlumberger VES data sets generated for multilayered (3-5 layers) geologic models and field VES data from ten (10) drilled sites in the Basement Complex areas were employed. RESIST version 1.0 software was used for the refinement of the preliminary interpretation results (layer parameters) obtained from model and field data. Statistical analysis of percentage deviations between model and final interpretation parameters was carried out; while composite plots of the interpreted and borehole derived depths were done. The error margins obtained in each of the conventional partial curve matching, asymptotes/inflection points and type curve-controlled guess technique respectively are significantly between ±10%;-30 and +40 % and-30 and +10 % in resistivity estimates; ±10%;-10 and +130 % and-40 and +100 % in depth estimates in the theoretical model data. The error margins in depth in the field data trial are significantly between-35 and +5 % for partial curve matching,-90 and +20 % for asymptotes/inflection points and-85 and-10 % for type curve-controlled guess technique. The partial curve matching interpretation technique gives the most consistently low percentage deviation error margins amongst the three VES preliminary interpretation techniques