LIFETIME PULSED NEUTRON/CHLORINE COMBINATION LOGGING TOOL

摘要

Methods and apparatus for logging a wellbore and determining a presence or absence of a hydrocarbon bearing formation are disclosed. A sonde includes a t least two gamma radiation detectors that are utilized for chlorine logging and lifetime logging in combination. Additionally, two detectors of the sonde are spaced axially from each other at different distances from the source to enable determination and compensation for various other parameters such as porosity and water flow velocity. Appropriate gating of the detectors enables sensing total counts of radiation emitted fr om adjacent formations and sensing of specific energy ranges of radiation when the formation is bombarded with energy. Signals from the lifetime logging enable adjustment o f the chlorine logging for a borehole effect and background radiation. The detecto rs can include a sheath of a high capture cross-section material that interacts wit h neutrons to produce gamma radiation to shield the detectors.