Developments in elemental concentration logging and applications

The past decade has seen a dramatic growth of gamma-ray spectroscopy logging as a tool for solving geophysical problems. Initial attempts generally provided relative elemental concentrations to estimate gross lithological structure, clay volume, and oil saturation. Developments in recent years have provided absolute elemental concentrations for a larger set of elements, using elemental analysis (including tracers) for solving many specific oil field problems, and providing a basis, through geochemical research, for developing a wide range of applications of borehole elemental analyses, such as chemically-described mineralogy, and physical properties that have been related to the mineral structure of the formation rock, such as cation exchange capacity, grain density, permeability, and source rock evaluation. It is now obvious that elemental logging is not yet a mature development. In this paper some areas of further development, both in the techniques of elemental logging and in the applications of the data are discussed