Method for analyzing formation data from a measuring-during-drilling logging instrument for assessing soil formations.

摘要

This invention relates to a method for analyzing data from a measurement-while-drilling (MWD) formation evaluation logging tool which compensates for rotations of the logging tool (along with the rest of the drillstring) during measurement periods. In accordance with this method, the received signal is broken down into a plurality of sections. In a preferred embodiment, the present invention calls for the breaking of the signal from the formation into four different sections: top, bottom, right, left. As the tool rotates, it will quickly pass through these four quadrants. Each time it passes a boundary, a counter is incremented, pointing to the next quadrant. This will allow for dividing the data into four spectra for each detector. Each of these four spectra will be obtained for 1/4th of the total acquisition time. The relative error is minimized by comparing the relative error in each spectrum and selecting a specific spectrum or by combining at least two spectra. In a gamma ray density tool having a pair of detector assemblies (e.g., long space and short space), the long space data, as well as the short space data, will have sufficient statistical significance for use in the measurment of the density. In this manner, four compensated density measurements can be obtained for each sample. These four measurements can be compared and combined to obtain an optimum density, and pseudo-caliper measurement.