Process, apparatus and system of forming time thermal decline

摘要

A novel neutron burst timing, detection, and calculation method and apparatus are disclosed for a Thermal Decay Time Logging System. A neutron bursting regime is provided which includes a short burst, long burst repetitive sequence. After a short delay from the short burst, a first series of time gates is provided for accumulating gamma ray counts. After a relatively longer delay from the long burst, a second series of time gates is provided for accumulating gamma ray counts. The thermal neutron decay time constant tau and the macroscopic capture cross-section SIGMA of the formation are determined through an iterative procedure by which the formation tau is estimated from the second series of time gates which have been stripped of borehole decay counts determined from the first series of time gates. Similarly, the borehole tau is estimated from the first series of time gates which have been stripped of formation decay counts determined from the second series of time gates.