Mineralogy from Geochemical Well Logging

Michael M. Herron
Schlumberger-Doll Research, Old Quarry Road, Ridgefield, Connecticut 06877

Abstract: Multivariate statistical analyses of geochemical, mineralogical, and cation-exchange capacity (CEC) data from a Venezuelan oil well were used to construct a model which relates elemental concentrations to mineral abundances. An r-mode factor analysis showed that most of the variance could be accounted for by four independent factors and that these factors were related to individual mineral components: kaolinite, illite, K-feldspar, and heavy minerals. Concentrations of Al, Fe, and K in core samptes were used to estimate the abundances of kaolinite, illite, K-feldspar, and, by subtraction from unity, quartz. Concentrations of these elements were also measured remotely in the well by geochemical logging tools and were used to estimate these mineral abundances on a continuous basis as a function of depth. The CEC was estimated from a linear combination of the derived kaolinite and illite abundances. The formation's thermal neutron capture cross section estimated from the log-derived mineralogy and a porosity log agreed well with the measured data. Concentrations of V, among other trace elements, were modeled as linear combinations of the clay mineral abundances. The measured core V agreed with the derived values in shales and water-bearing sands, but exceeded the day-derived values in samples containing heavy oil. The excess V was used to estimate the V content and API Gravity of the oil. The log-derived clay mineralogy was used to help distinguish nonmarine from transitional depositional environments. Kaolinite was the dominant clay in nonmarine deposits, whereas transitional sediments contained more illite.

Key Words: Elemental analysis • Illite • Kaolinite • Mineralogical analysis • Multivariate analysis • Neutron capture cross section • Well logging

Clays and Clay Minerals; April 1986 v. 34; no. 2; p. 204-213; DOI: 10.1346/CCMN.1986.0340211
© 1986, The Clay Minerals Society
Clay Minerals Society (www.clays.org)