ABSTRACT

Lithological determinations were made on the same electric log by a group of 12 electric-log specialists, another group of 39 geologists, and a student assistant. The geologists and student assistant used a standardized mechanical procedure. Thirty-three attributes were calculated from each set of data. The results indicate that no greater differences in interpretation are to be expected if standardized mechanical procedures such as that used in this test are practiced instead of conventional inflection-point methods. Minimization of interpretive differences is probably best attained by having the data collected by one operator using a standardized procedure. Variations from one company to another are indicated. Studies of the ranked coefficients of variance show centre of gravity and standard-deviation attributes to be subject to less variance than simpler attributes such as sand/shale ratio. Skewness and kurtosis data occupy an intermediate position.