US 4,046,764 A · Method and apparatus for measuring the thermal neutron absorption rate in earth formations

Abstract

Circuitry is provided for establishing the points in time at which radiation is detected following each neutron burst in pulsed neutron logging. Means are provided to generate a signal indicative of the arithmetic mean to then compute the macroscopic thermal neutron capture cross section of the formation of interest surrounding the borehole. In one embodiment, an indeterminate number of gates provides a means of establishing the point in time of each pulse indicative of detected radiation. In another embodiment, only a predetermined number of such gates are used. In yet another embodiment, a weighting factor is applied to pulses occurring either before or after the arithmetic mean such that the number of pulses before the arithmetic mean are a multiple of the number occurring after such time.

Claims5

Dependent claims

Apparatus for investigating the character of earth substances and the like, comprising:

means for irradiating said substances with a burst of neutrons;
means for detecting radiation occasioned in said irradiated substances by said burst of neutrons during a preselected time interval following said burst of neutrons and for generating electrical pulses indicative of said detected radiation;
circuit means for determining the time relationship of each of said electrical pulses with respect to said time interval;
circuit means for determining the arithmetic mean of said electrical pulses as determined with respect to said time interval;
and
circuit means for computing the macroscopic thermal neutron capture cross section from the said arithmetic mean based upon the following relationship:
##EQU14## where .SIGMA. = macroscopic thermal neutron capture cross section
K.sub.0 = a first constant
K.sub.1 = a second constant
V = speed of thermal neutrons
t = arithmetic mean of said electrical pulses.

8 more elements

Dependencies are inferred from the claim text.

Method and apparatus for measuring the thermal neutron absorption rate in earth formations

Life of this patent

Method and apparatus for measuring the thermal neutron absorption rate in earth formations

Life of this patent

Abstract

Claims5