Method for computing dip of earth formations from wellbore image data

Abstract

A method for calculating the orientation of a geologic feature with respect to the axis of a wellbore drilled through earth formations. The method uses finely detailed measurements of a selected property of the earth formations made along the wall of the wellbore. The method includes the steps of segregating the finely detailed measurements by an angle subtended with respect to an arbitrary reference on the circumference of the wellbore. The measurements are further segregated into a selected axial interval along the wellbore. For each segment, for each subtended angle, the segregated measurements are spectrally analyzed with respect to spatial frequency. Coefficients of a best fit curve are determined for the phase components of the spectrally analyzed measurements with respect to the subtended angle. The orientation of the geologic feature is calculated from the best fit curve. In the preferred embodiment a noise floor is calculated in each segment by stacking the amplitude components at each spatial frequency in each interval. For each spatial frequency, the stacked amplitude is compared to the noise floor. Only spatial frequencies having amplitudes above the noise floor are used to generate the best fit curve from their respective phase components.