Method for logging a borehole employing dual radiation detectors.

摘要

For logging a borehole, a sonde (16) having a source (20) of penetrating radiation and at least two longitudinally-spaced radiation detectors (26,36), is passed within a borehole. Count rate data are produced by each of the detectors and are continuously compared to predetermined count rate relationship which may be obtained from detectors operating in reference standard boreholes. In accordance with this count rate data comparison, the suitability of either the <<ratio>> or <<spine/rib>> analytical method is determined and the appropriate technique is automatically applied to produce an indication of a logged parameter such as formation porosity, selctively compensated for a borehole environmental condition such as variations in borehole diameter.