Patent ID: 9551213
Date: 2017-01-24
CPC Classifications: E21B

Claim:
1. A method of drilling an earth formation, comprising: conveying a sensor on a drill string in a wellbore penetrating the earth formation; using the sensor to measure a formation parameter from the earth formation at a plurality of depths in the wellbore, wherein the formation parameter is indicative of bulk shale volume; using a downhole processor to: produce a plurality of distributions of the formation parameter, wherein a selected distribution of the plurality of distributions corresponds to a selected depth and includes the formation parameter measurements obtained at the selected depth; produce a cumulative distribution of the formation parameter from the plurality of distributions; estimate a clean shale response using maximum values from both of a distribution for a selected depth and the cumulative distribution; estimate a clean sand response using minimum values from both of the distribution for the selected depth and the cumulative distribution; create a scale related to bulk shale volume from the clean shale response and the clean sand response; compare a value of the formation parameter sampled from the selected depth of the formation to the created scale to estimate the bulk shale volume of the formation at the selected depth; and alter a drill string direction to drill the wellbore in the formation along a selected profile indicated by the bulk shale volume.