| 摘要 |
Illustrative embodiments of the present invention include methods and apparatus for processing geophysical signals derived from sources located at different positions in a borehole to obtain displacements which are then combined to determine the relative position of formation characteristics. The geophysical signals are correlated by pairs using substantially overlapping correlation intervals to obtain sequences of displacements for each pair. Displacements from each sequence are combined in possible corresponding relationships and classified in an angular classification system relative to the position of the sources of the correlated signals. Displacements from overlapping sequences are also combined and classified, and an analysis is then performed on the classified combinations to determine which combinations are valid. Invalid displacements, for example, are sometimes produced by the failure of the borehole tool used to derive the signals to remain in the preferred position in deviated holes. An analysis for the exaggeration of certain relationships allows detection and rejection of the associated displacements. Apparently poor quality displacements, although perhaps invalid or inaccurate, are not discarded, even where enough apparently good quality displacements are present. Instead, all possibly corresponding displacements are considered for analysis. In the analysis, displacement combinations including invalid displacements form groups separate from valid combinations. Combinations including inaccurate displacements form groups about the valid combinations and aid in defining the position of the valid group. With the position of the valid group located, combinations from each sequence of displacements which belong to this group may then be retrieved and used to determine the corresponding relative position of the formation characteristic. When applied to dipmeter signals, the method produces more accurate and geologically consistent dip and azimuth values for subsurface formations.
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