Neutron logging tool with multiple detectors

摘要

A neutron logging tool has multiple detectors spaced about the circumference of the tool. The detectors are shielded from each other such that each detector detects gamma rays from the area of the borehole and formation to which it is closest. The log readings from each detector can be associated with the orientation of that detector. The orientation-specific log readings can then be aggregated to form an azimuthal log which can be used to analyze pre-fractured and/or post-fractured formations.

主权项

1. A neutron logging tool for obtaining an azimuthal log of a borehole, the tool comprising:
a housing deploying in the borehole and having a neutron source; an orientation instrument disposed on the housing and determining orientation data of the housing in the borehole; a plurality of gamma ray detectors disposed about a circumference of the housing and displaced at longitudinally different distances from the neutron source, the gamma ray detectors adapted to detect gamma ray data as individual logs from portions of a formation surrounding the borehole; and a shielding at least partially shielding each of the gamma ray detectors and at least partially focusing the sensing by each of the gamma ray detectors towards a sensing direction away from the housing, wherein the individual logs from the detected gamma ray data of the gamma ray detectors are combined with different weightings into the azimuthal log of the borehole.