1984/04/01 by C. Clavier, G. Coates, George R. Coates +2
Chemistry · Computer Science · Earth and Planetary Sciences · Environmental Science · #Chemistry #Computational chemistry #Computer science #Conductivity #Geochemistry and Geologic Mapping #Geology #Geophysical and Geoelectrical Methods #Geotechnical engineering #Groundwater flow and contamination studies #Interpretation (philosophy) #Mineralogy #Petroleum engineering #Petrophysics #Physical chemistry #Physics #Porosity #Soil science #Thermodynamics #Water model
paper · doi:10.2118/6859-pa
crossref issued 1984/04/01 · crossref published 1984/04/01 · crossref published-online 1984/04/01 · crossref published-print 1984/04/01 · openalex publication_date 1984/04/01 · crossref created 2007/12/07 · crossref deposited 2022/02/28 · openalex created_date 2025/10/10 · crossref indexed 2026/08/05 · openalex updated_date 2026/08/05
Abstract A simple petrophysical model proposed by Waxman and Smits (WS)1 in 1968 and Waxman and Thomas (WT)2 in 1972 accounts for the results of an extensive experimental study on the effects of clays on the resistivity of shaly sands. This model has been well accepted by the industry despite a few inconsistencies with experimental results. It is proposed that these inconsistencies resulted from the unaccounted presence of salt-free water at the clay/water interface. Electrochemistry indicates that this water should exist, but is there enough to influence the results? Both a theoretical study and reinterpretation of Waxman-Smits-Thomas data show that there is. The corresponding new model starts from the Waxman and Smits concept of supplementing the water conductivity with a conductivity from the clay counterions. The crucial step, however, is equating each of these conductivity terms to a particular type of water, each occupying a representative volume of the total porosity. This approach has been named the "dual-water" (DW) model because of these two water types—the conductivity and volume fraction of each being predicted by the model. The DW model has been tested on most of the core data reported in Refs. 1 and 2. The DW concept is also supported by log data3 and has been successfully applied to the interpretation of thousands of wells. However, the scope of this paper remains limited to the theoretical and experimental bases of the DW model.