A New Technique for Deriving the Resistivity Parameters of Archie's Equation From Combination of Logs and Core Measurements

Abstract

ABSTRACT A new approach in determining the parameters of the Archie's equation a, m and n is presented in this paper. It is based on the use of water saturation from the core or from an EPT type measurement and the resistivity of the formation where this water saturation is known. The proposed method is an extension to a 3D space of the usual regression technique used in a plane, as in the laboratory determination of m and n. Both a spatial visualization and a regression may be used to obtain the Archie parameters. This method may be applied in different situations: –in a reservoir at any water saturation in a well drilled with a waterbase mud where both MSFL and EPT type logs have been run.–in a reservoir at irreducible water saturation and in a well drilled with a tagged oil base mud of known water loss where the resistivity of the formation is measured by an induction tool and the water saturation is known from either the core or an EPT type tool.–in a reservoir at residual oil saturation (after a waterflood), in a well drilled with a waterbase mud where the resistivity of the formation is measured by a long spacing resistivity tool and the water saturation is known from either an EPT type log or a core. Examples are given of the use of this technique in a carbonate field of the Middle East from two different reservoirs: The high heterogeneity of the first reservoir makes it necessary to sort the data per lithofacies and therefore reduces the number of data points, whereas in the second, more homogeneous results are fairly straight forward and provide an answer close to the accepted triplet (1,2,2) for (a, m, n).