Method and tool for neutron lifetime logging.

摘要

A borehole logging tool (10) for neutron lifetime logging of subterranean formations (23,24) surrounding a borehole includes a pulsed source of fast neutrons and at least one radiation detector (20) for measuring the radiation returning to the borehole from the irradiated formations surrounding the borehole. A radiation detector pad (13) houses the radiation detector (20) and a shielding material (13). An articulating arm (22) moves the radiation detector pad against the borehole wall and azimuthally orients the pad so that the radiation detector is firmly pressed against the formation so as to track most borehole enlargements as the tool is advanced through the borehole. The shielding material minimizes by moderation and/or absorption secondary radiation from the borehole fluid.