Log analysis for unconventionals
This page is currently being authored by a graduate student at the University of Houston. This page will be complete by November 3, 2017.
Shale volume estimation
The estimation of the shale volume in the zone of interest can be performed in the available wells using the normalized version of the Gamma-Ray log (GRn), and using both neutron and density porosity logs. Following the concept that the increase in radioactivity of the organic-rich shales is related to their organic matter content, the GR and spectral GR responses need to be corrected for uranium before estimating clay content. This element forms compounds that sorbs to clays and organic material in both cases where their depositional environment is anoxic marine or oxidizing lacustrine (Ahmed and Meehan, 2016). In case spectral GR data are not available for a particular well, its correction for uranium should be conducted by means of a linear empirical relationship constructed using both, the corrected spectral GR of another well in the area of interest plotted against its original log (Figure XX). The following equation is used for the GR correction for uranium:
Where, GRc=corrected GR, GR=total GR, and U=uranium in ppm.
Corrected Spectral GR for Well B, color‐coded by formation. The correlation between both GR responses allows an adequate linear fit of 0.981. The linear empirical relationship is used to calculate the corrected GR for uranium in the Well A.]]