Doctor of Philosophy (PhD)
Researchers at Louisiana State University, LSU, have introduced several petrophysical models expressing the electric properties of shaly sands. These models, to be used for hydrocarbon detection, are based on the Waxman and Smits concept of supplementing the water conductivity with a clay counterions conductivity. The LSU models also utilize the Dual Water theory, which relates each conductivity term to a particular type of water, free and bound, each occupying a specific volume of the total pore space. The main difference between these models and the other shaly sand models is that the counterion conductivity is represented by a hypothetical sodium chloride electrolyte. This study introduces a modified version of early LSU models. This modified model eliminates a questionable assumption incorporated in all previous shaly sand models. Previous models use same formation resistivity factor for all terms in the model. The proposed model considers that the electric current follows the effective porosity path in the term representing the free electrolyte and follows the clay porosity path in the term representing bound water. The differentiation between the two paths is accomplished by using two different formation factors one in the free water and another in the bound water term of the model. It also used two different cementation exponents to express formation factors in terms of porosity. The validity of the new model was checked using cation exchange capacities measured on core samples and drill cuttings. Calculated cation exchange capacities display good agreement with the measured cation exchange capacities. The water saturation calculated using the new model are more representative of hydrocarbon potential of the zones of interest. In addition, cation exchange capacity calculated using this modified model and log data acquired during drilling has shown potential for diagnosis of pending bit balling of PDC bits drilled with water based mud in overpressured shale.
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Ipek, Gamze, "Log-derived cation exchange capacity of shaly sands : application to hydrocarbon detection and drilling optimization" (2002). LSU Doctoral Dissertations. 2727.