Semivariogram Modelling of Porosity and Permeability of Ikphesi Dolomitic Marble, Akoko Edo L.G.A, Edo State Using Microsoft Excel Package

Abstract

Damilola Johnson Afu, Adekunle Ekun, Cosmas Afolabi, Ayodele Gbenga and Fiyinfoluwa Fatuase

This paper demonstrates Semivariogram modelling of physical properties (porosity and Permeability) and its procedure for Ikphesi dolomitic marble deposit Akoko Edo L.G.A, Edo State, Nigeria. Forty two (42) dolomite samples were collected at pre- determined distance (6m interval depending on the pit size and horizontal level). Porosity and permeability values for the test samples were determined from the laboratory using ASTM Standard Test Method C97-83, and ASTM Standard Test Method D 4525-90. Semivariogram values for different distances covered and number of pairs were determined using Microsoft Excel package. Experimental semivariogram plots for both permeability and porosity values were done in East-West and North- South directions to determine the semivariogram properties (sill, nugget effect, and range). Final modelling for porosity and permeability of the data set (values) were performed. Semivariograms were constructed for each of the properties and the distribution patterns of the samples were identified from the plot. The spherical model for permeability from the plots for the models in W-E and N-S directions, the patterns of distribution-n are not similar, which suggest that permeability within the deposit are anisotropic in nature, while in the spherical model for porosity, the pattern of distribution both in the W-E and N-S direction are similar, that is isotropic in nature. Semivariogram model should be performed in all directions to determine the nature of mineral properties whether anisotropic or isotropic.

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