R.J. van den Cord
Koninklijke/Shell E&P Laboratorium
ABSTRACT
Analyses are presented of several field tests with the geochemical logging tool (GLT), a recently introduced contractor tool. Our investigations were directed towards the assessment of the accuracy with which the GLT measures the in-situ elemental composition and then converts the data into formation characteristics such as mineralogy, matrix density and permeability. We conclude that elemental concentrations are satisfactorily estimated but that standard contractor software does not (yet) accurately quantify the desired petrophysical properties.
The estimation of elemental concentrations was examined by comparison with core measurements. After allowances for the vertical resolution of the tool had been made, a satisfactory correspondence with core data was obtained. Knowledge of the elemental composition in situ can be important in applications such as well-to-well correlation and facies recognition.
Petrophysical characteristics are obtained from the measured elemental concentrations by means of contractor processing based on world-wide correlations. As a result of our comparisons with core data from several fields, we conclude that only for the matrix density does this procedure prove to be acceptably accurate. For the other characteristics, calibration with local (field) core data seems to be required. However, the full potential of such an approach still needs further study.