Correlation Between Gamma Ray, Density and Neutron Logs and Whole Rock Elemental Geochemistry Using a Neural Network Model

Smith, Christopher N.¹; Assous, Said²; Busch, Rainer¹
¹Geoscience Development, Weatherford International, Houston, TX.
²Geoscience Development, Weatherford International, East Leake, United Kingdom.

Gamma ray, density and neutron logs are compared to synthetic logs modeled from whole rock geochemical analyses. Lithology, mineralogy, gamma response and density are calculated from elemental abundances determined from core and cuttings samples and compared to log plots. There is excellent agreement between the geochemical and wireline log plots. Differences between the plots can be attributed to the point resolution and increased accuracy of rock properties derived from the geochemical analyses and the homogenization of lithology and density over the resolution of the logs. Elemental ratios can also be correlated directly to the logs: K/Al, Rb/Al and U/Th correlate to gamma response; Ca/Mg, Si/Al, and Ti/Al correlate to limestone, dolomite, shale and sandstone lithotypes. Whole rock geochemical analyses can be obtained in near real time from cuttings at the wellsite and thus offer an opportunity for increased accuracy in stratigraphic correlation and geosteering while drilling.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012