Abstract: In accordance with illustrative embodiments of the present invention, methods for processing well logging data comprises deriving measurements of a plurality of earth formations parameters and combining these measurements in a new manner to enable interpretation of shales and shaly sand type formations. More particularly, measurements of a plurality of the hydrogen index, bulk density, radially deep and shallow resistivity, spontaneous potential, acoustic travel time and natural formation radioactivity content are made and combined in a manner to produce data useful in evaluating shales and shaly sand type formations.

Abstract: In order to determine dips of subsurface formations more reliably, a dipmeter tool with three or more transducers, spaced circumferentially around the borehole wall, is used and the transducer outputs are correlated in a novel way to provide redundant indications of displacements between the depths at which respective transducers intercept a given layer. These redundant displacements are processed to single out at each given level only those displacement pairs which result in the most consistent dips over several mutually overlapping depth intervals called zones. Consistency is established in each zone without regard to a neighboring zone, to avoid any long range bias.

Abstract: 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.