Method and apparatus for downhole sensing using neutron pulses and gamma radiation measurements

摘要

A method and apparatus for characterizing the properties of the region surrounding a borehole. In one embodiment, a downhole tool including a neutron generator is used to generate neutron pulses into the region surrounding the borehole. A detector in the downhole tool detects gamma radiation pulses resulting from the capture of neutrons by elements in the surrounding region. For each gamma radiation pulse, a record is made of its amplitude and the time that the pulse was detected, measured to a resolution of a few microseconds. The amplitude/timestamp data is stored in memory in the tool for later retrieval. The data generated is stored in memory and interpretation can be made by the operator or log analyst after the memory module data has been transferred from the tool.

主权项

1. A method of measuring properties of a formation surrounding a borehole, comprising:
(a) directing a neutron burst into the formation; (b) detecting gamma radiation pulses resulting from the capture of neutrons by elements in the formation; (c) for each detected gamma radiation pulse, recording a time value and a pulse amplitude value.