Underground strata investigation partic. of oil bearing formations - using fast neutron and detection of resultant gamma radiation

摘要

In the investigation of earth strata traversed by a borehole by measuring their time-dependent neutron characteristics, (a) the strata, are irradiated by fast neutron pulses, (b) data are produced of the gamma ray energies generated by neutron interactions related to the fast neutron pulse (c) at least part of the gamma ray energy spectrum, corresponding with the neutron pulse relative representations, is produced during a first time interval and (d) the information from the first time interval is controlled as a function of the measurement derived from the time-dependent neutron characteristic of the formation, and preferably produced from representations of neutron interactions with nuclei in the strata after irradiation with a second neutron pulse and its production of the measurement of a neutron characteristic of the formation from the representations relative to the second neutron pulse. Extra data is obtained, particularly in the case of boreholes with a tubular liner, related to the location and productivity of hydrocarbon-containing strata.