The Use of Electromagnetic Mixing Rules for Petrophysical Evaluation of Dual- and Triple-Porosity Reservoirs

Abstract

Summary Electromagnetic mixing rules such as the Maxwell-Gamett rule, the Bruggeman equation, and the coherent-potential formula, are shown to be useful for the evaluation of the porosity exponent m in naturally fractured reservoirs represented by dual- and tripleporosity models. Comparisons are made with core data from limestone, dolomite, and tight gas reservoirs to corroborate results from the theoretical models. Rigorous values of m reduce the uncertainty in the calculated values of water saturation and, thus, improve the estimates of hydrocarbons in place and recoveries, particularly in situations in which sufficient data are not available to use the material-balance approach. The main advantage of the new method developed in this paper for petrophysical analysis is that it can handle, with the use of a single equation, the individual mixing rules previously mentioned, and at the same time, depending on the availability of data, it can quantify the values of matrix, fracture, and nonconnected-vug porosity, and the porosity exponent of the total porosity system. It is concluded that electromagnetic mixing rules provide a useful methodology for the petrophysical evaluation of complex dual- and triple-porosity reservoirs.