Step 1: Lithology Using the Gamma Ray log, define a shale base line ILD (deep) Using the Gamma Ray log, define a shale base line Deflections far to the left are sands Intermediate deflections to the left are silts Gamma Ray Caliper Sandstone Siltstone Shale MSFL NPHI SFL RHOB) SLIDE 11 First we can interpret lithology based on the gamma log Red dashed line = shale baseline Depth range subdivided into 3 litho-types High gamma, near baseline = shale (green) Low gamma = sandstone (yellow) Intermediate = silt (brown) Courtesy of ExxonMobil L 4 - Well Log Data