Determining resistivity anisotropy and formation structure for vertical wellbore sections
Abstract:
Formation properties in a vertical section of a wellbore are determined by considering the vertical section as consisting of one or more segments. Measurements are obtained with a directional resistivity tool at two or more measurement stations within each segment for which the complex 0th harmonic coefficients for the obtained measurements are non-trivially different from one another. For each such segment, the phase shift and attenuation are determined using the complex 0th harmonic coefficients obtained for that segment and an inversion is performed for the formation properties using the determined phase shift and attenuation for that segment. Formation properties for that segment may be output to a display or memory storage device. For certain segments, one or more gain factors may be obtained. The gain factors are used to correct the measured voltages for certain neighboring segments and the corrected voltages inverted to obtain anisotropy and formation structure.
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