ABSTRACT

Since many log readings are substantially affected by clay in the formation, a reliable evaluation of the clay content is essential in formation evaluation from logs. The method presented to solve this complex problem is based on the consideration of several "clay indicators" evaluated statistically over the interval of the well to be interpreted. These indicators are either single curves such as the SP, Gamma Ray, or Neutron, or combinations of two curves such as Neutron and Density logs. Each clayindicator is calibrated so as to give either the actual clay content or an upper limit of that value. Then the lowest of these indications is likely to be very close to the actual value. The method is applicable not only for shaly sands, but also for complex lithologies.

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