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EMPIRICAL TRANSMISSIVITY MODELING OF PEDESTRAL AQUIFER OF IVORY COAST

2016; Research Laboratory in Subterranean and Surface Hydraulics; Issue: 25 Linguagem: Inglês

1112-3680

A.M. Kouassi, M. C. Loba, K.A. Kouamé, Koffi Fernand Kouamé, Jean Biémi,

Hydraulic Fracturing and Reservoir Analysis

The objective of this study is modeling the transmissivity of the hard rock aquifers from the specific capacity. The areas tested used for this study are the region of N'zi-Comoe (Paleoproterozoic domain) and Guiglo-Duekoue region (Archean-SASCA domains). A large database of transmissivity and specific capacity values was compiled. The methodological approach is based on the study of the relationship between the transmissivity and specific capacity from an empirical procedure of the form T=αQ s β . The quality of the developed models was analyzed from the correlation coefficient, the Student t test, the bias on the mean and the square root of the quadratic error. The values of specific capacity in the Guiglo-Duekoue region ranging from 1.427.10 -2 to 2.571 m 2 /h with an average of 0.279 m 2 /h and a coefficient of variation of 159%. The medium and high specific capacities represent 61.22%. As for the region of the N'zi-Comoe, the specific capacity range from 7.752.10 -3 to 3.03 m 2 /h with an average of 0.402 m 2 /h, a variation coefficient of 116% and a rate of 82% in respect of the medium and high specific capacities. The transmissivity values of Guiglo-Duekoue region fluctuate between 1.779.10 -3 to 1.952 m 2 /h with an average of 0.283 m 2 /h and a coefficient of variation of 135%. Average and high drilling transmissivity represent 73.47%. As regards the region of the N'zi-Comoe, the transmissivity varies between 6.2.10 -3 to 1.302 m 2 /h with an average of 0.196 m 2 /h and a coefficient of variation of 123%. Drilling with medium and high transmissivity values are estimated at 68.66%. The results of the adjustment showed that the transmissivity and the specific capacity, processed by the log function follows the normal distribution. The distribution of variables according to lognormal therefore possible to envisage a model of the relationship T=f (Q s ). Thus, two powerful empirical relationships have been established. Both models are designed respectively T 1 =0.354Q s 0.8544 with R 2 =0.70 for the region of N'zi-Iffou-Moronou (region of N'zi-Comoe) and T 2 =1.086Q s 1.187 with R 2 =0.60 for the Guiglo-Duekoue region. These empirical models may be useful for other aquifers with similar hydrogeological conditions. However, these models could be improved by correcting the specific capacity losses.