Methods and apparatus for measuring the density of geological formations

Claim 3

A method according to claim 1 and further including the steps of: determining the adjusted threshold energy value; and selecting only those detected gamma radiation energies above then adjusted threshold energy value to correct borehole barite effects on detected gamma radiation.

Claim 6

A method according to claim 3 wherein the reference signal is representative of the mean amplitude of a second spectrum of gamma radiation that exceeds the threshold energy value, the second spectrum being representative of formation gamma radiation in the absence of borehole barite.

Claim 7

A method according to claim 3, wherein said first comparing step comprises comparing gamma radiation energies detected from a formation of interest to a threshold energy value to produce an electrical output representative of detected gamma radiation that exceeds the threshold energy value and, in response to the electrical output, to produce a first signal representative of a first spectrum of detected gamma radiation that exceeds the threshold energy value.

Claim 8

A method according to claim 3, wherein the reference signal is representative of the median amplitude of a second spectrum of gamma radiation that exceeds the threshold energy value, the second spectrum being representative of formation gamma radiation in the absence of borehole barite.

Claim 9

A method according to claim 3, wherein said second comparing step comprises: comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds the threshold energy value, the second spectrum being representative of formation gamma radiation in the absence of borehole barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds the reference amplitude and is free of borehole barite distortion; combining the first signal and the first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between the threshold energy value and the reference amplitude; and comparing the first intermediate signal to the second intermediate signal to produce a second signal representatiVe of a variation from a predetermined relationship therebetween.

Claim 10

A method according to claim 3, wherein said second comparing step comprises: comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds the threshold energy value, the second spectrum being representative of formation gamma radiation in the absence of borehole barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds the reference amplitude and is free of borehole barite distortion; combining the first signal and the first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between the threshold energy value and the reference amplitude; and comparing the first intermediate signal to the second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween; and further wherein said adjusting step comprises selecting either one of the first signal or, in response to the second signal, the first intermediate signal so that borehole barite effects are corrected for in the selected of the two signals and a formation characteristic free of barite distortion can be determined from the selected of the first signal and the first intermediate signal.

Claim 11

A method according to claim 3 and further including, after said first comparison step, the step of comparing the detected gamma radiation energies to a cut-off energy value representative of a maximum energy level for a formation characteristic determining spectra to produce an inhibiting signal representative of detected gamma radiation that exceeds the cut-off value for provision to said circuit means and wherein said second step comparison of said first signal to said reference signal is inhibited in response to said inhibiting signal.

Claim 18

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to obtain a formation characteristic free of barite distortion comprising: means for deriving a plurality of spectra of detected gamma radiation energies that are representative of detected formation gamma radiation and exceed a threshold energy value; and means connected to said spectra deriving means for comparing said spectra with one another to produce an output signal representative of a predetermined relationship therebetween to enable determination from said output signal of an adjusted threshold energy value corresponding to a minimum energy level for a formation characteristic determining spectra that results in the correction of borehole barite effects on said detected gamma radiation spectra so that a formation characteristic functionally dependent on detected gamma radiation and free of barite distortion can be obtained.

Claim 19

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to obtain a formation characteristic free of barite distortion comprising: means for deriving a plurality of spectra of detected gamma radiation energies that are representative of detected formation gamma radiation and exceed a threshold energy value; and means connected to said spectra deriving means for comparing said spectra with one another to produce an output signal representative of a predetermined relationship therebetween to enable determination from said output signal of an adjusted threshold energy value corresponding to a minimum energy level for a formation characteristic determining spectra that results in the correction of borehole barite effects on said detected gamma radiation spectra so that a formation characteristic functionally dependent on detected gamma radiation and free of barite distortion can be obtained.

Claim 20

Apparatus according to claim 13, further including means for determining said adjusted threshold energy value including means for selecting only those detected gamma radiation energies above said adjusted threshold energy value to correct borehole barite effects on detected gamma radiation.

Claim 21

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: first comparison means for comparing gamma radiation energies detected from a formation of interest to a threshold energy value to produce a first signal representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value; circuit means connected to said first comparison means for comparing said first signal to a reference signal representative of formation gamma radiation in the absence of borehole barite to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said circuit means for adjusting said threshold energy value in response to said second signal to correct borehole barite effects on detected gamma radiation so that a formation characteristic free of barite distortion can be determined.

Claim 22

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: first comparison means for comparing gamma radiation energies detected from a formation of interest to a threshold energy value to produce a first signal representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value; circuit means connected to said first comparison means for comparing said first signal to a reference signal representative of formation gamma radiation in the absence of borehole barite to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said circuit means for adjusting said threshold energy value in response to said second signal to correct borehole barite effects on detected gamma radiation so that a formation characteristic free of barite distortion can be determined.

Claim 23

Apparatus according to claim 15, wherein said reference is signal is representative of the mean amplitude of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehole barite.

Claim 24

Apparatus according to claim 15, wherein said first comparison means comprises means for comparing gamma radiation energies detected from a formation of interest to a threshold energy value to produce an electrical output representative of detected gamma radiation that exceeds said threshold energy value and, in response to said electrical output, to produce a first signal representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value.

Claim 25

Apparatus according to claim 15, wherein said reference signal is representative of the median amplitude of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehole barite.

Claim 26

Apparatus according to claim 15, wherein said second comparison means comprises: means for comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehole barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds said reference amplitude and is free of borehole barite distortion; first circuit means connected to said first and second comparison means for combining said first signal and said first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between said threshold energy value and said reference amplitude; and second circuit means connected to said first comparison means and said first circuit means for comparing said first intermediate signal to said second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween.

Claim 27

Apparatus according to claim 15, wherein said second comparison means comprises: means for comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehole barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds the reference amplitude and is free of borehole barite distortion; first circuit means connected to said first and second comparison means for combining said first signal and said first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pUlses between said threshold energy value and said reference amplitude; and second circuit means connected to said first comparison means and said first circuit means for comparing said first intermediate signal to said second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween; and further wherein said adjusting means comprises means connected to said second circuit means for selecting either one of said first signal or, in response to said second signal, said first intermediate signal so that borehole barite effects are corrected for in the selected of said two signals and a formation characteristic free of barite distortion can be determined from the selected of said first signal and said first intermediate signal.

Claim 28

Apparatus according to claim 15, further including means for generating said threshold energy value for provision to said first comparison means, said threshold energy value being representative of a minimum energy level for a formation characteristic determining spectra that results in the correction of borehole barite effects on the spectra of detected gamma radiation energies, and wherein said comparison means is connected to said generating means.

Claim 29

Apparatus according to claim 15, wherein said adjusting means is connected to said circuit means and said generating means for adjusting said threshold energy value.

Claim 30

Apparatus according to claim 15, further including second comparison means for comparing said detected gamma radiation energies to a cut-off energy value representative of a maximum energy level for a formation characteristic determining spectra to produce an inhibiting signal representative of detected gamma radiation that exceeds said cut-off value for provision to said circuit means and wherein said circuit means is connected to said first and second comparison means and further includes means for inhibiting comparison of said first signal to said reference signal in response to said inhibiting signal.

Claim 31

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: means for generating a threshold energy value representative of a minimum energy level for gamma radiation detected from a formation; means connected to said generating means for comparing gamma radiation energies detected from a formation of interest to said threshold energy value to produce an electrical output representative of detected gamma radiation that exceeds said threshold energy value; circuit means connected to said comparison means for comparing, in response to said electrical output, a first signal representative of detected gamma radiation and a reference signal representative of a second spectrum of gamma radiation pulses that exceed the threshold energy value, the second spectrum being representative of formation gamma radiation in the absence of borehold barite, to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said circuit means for adjusting said threshold energy value in response to said second signal to conform said first signal and said reference signal to said predetermined relationship so that borehole barite effects on said electrical output are corrected and a formation characteristic free of barite distortion can be determined.

Claim 32

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: means for generating a threshold energy value representative of a minimum energy level for gamma radiation detected from a formation; means connected to said generating means for comparing gamma radiation energies detected from a formation of interest to said threshold energy value to produce an electrical output representative of detected gamma radiation that exceeds said threshold energy value; circuit means connected to said comparison means for comparing, in response to said electrical output, a first signal representative of detected gamma radiation and a reference signal representative of a second spectrum of gamma radiation pulses that exceed the threshold energy value, the second spectrum being representative of formation gamma radiation in the absence of borehold barite, to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said circuit means for adjusting said threshold energy value in response to said second signal to conform said first signal and said reference signal to said predetermined relationship so that borehole barite effects on said electrical output are corrected and a formation characteristic free of barite distortion can be determined.

Claim 33

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: means for generating a threshold energy value representative of a minimum energy level for gamma radiation detected from a formation; first comparison means connected to said generating means for comparing gamma radiation energies detected from a formation of interest to said threshold energy value to produce a first signaL representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value; second comparison means for comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehold barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds said reference amplitude and is free of borehole barite distortion; first circuit means connected to said first and second comparison means for combining said first signal and said first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between said threshold energy value and said reference amplitude; second circuit means connected to said first comparison means and said first circuit means for comparing said first intermediate signal to said second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said second circuit means for adjusting said threshold energy value in response to said second signal to conform said first and second intermediate signals to said predetermined relationship so that borehole barite effects on said first signal are corrected and a formation characteristic free of barite distortion can be determined.

Claim 34

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: means for generating a threshold energy value representative of a minimum energy level for gamma radiation detected from a formation; first comparison means connected to said generating means for comparing gamma radiation energies detected from a formation of interest to said threshold energy value to produce a first signaL representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value; second comparison means for comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehold barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds said reference amplitude and is free of borehole barite distortion; first circuit means connected to said first and second comparison means for combining said first signal and said first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between said threshold energy value and said reference amplitude; second circuit means connected to said first comparison means and said first circuit means for comparing said first intermediate signal to said second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said second circuit means for adjusting said threshold energy value in response to said second signal to conform said first and second intermediate signals to said predetermined relationship so that borehole barite effects on said first signal are corrected and a formation characteristic free of barite distortion can be determined.

Claim 35

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: first comparison means for comparing gamma radiation energies detected from a formation of interest to a threshold energy value to produce a first signal representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value; second comparison means for comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehole barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds the reference amplitude and is free of borehole barite distortion; first circuit means connected to said first and second comparison means for combining said first signal and said first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between said threshold energy value and said reference amplitude; second circuit means connected to said first comparison means and said first circuit means for comparing said first intermediate signal to said second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said second circuit means for selecting either one of said first signal or, in response to said second signal, said first intermediate signal so that borehole barite effects are corrected for in the selected of said two signals and a formation characteristic free of barite distortion can be determined from the selected of said first signal and said first intermediate signal.

Claim 36

Apparatus for correcting borehole barite effects on gamma radiation detected from a formation of interest to determine a formation characteristic free of barite distortion comprising: first comparison means for comparing gamma radiation energies detected from a formation of interest to a threshold energy value to produce a first signal representative of a first spectrum of detected gamma radiation that exceeds said threshold energy value; second comparison means for comparing gamma radiation energies detected from a formation of interest to a reference signal representative of a second spectrum of gamma radiation that exceeds said threshold energy value, said second spectrum being representative of formation gamma radiation in the absence of borehole barite, to produce a first intermediate signal representative of a spectrum of gamma radiation that exceeds the reference amplitude and is free of borehole barite distortion; first circuit means connected to said first and second comparison means for combining said first signal and said first intermediate signal to produce a second intermediate signal representative of detected gamma radiation pulses between said threshold energy value and said reference amplitude; second circuit means connected to said first comparison means and said first circuit means for comparing said first intermediate signal to said second intermediate signal to produce a second signal representative of a variation from a predetermined relationship therebetween; and means connected to said second circuit means for selecting either one of said first signal or, in response to said second signal, said first intermediate signal so that borehole barite effects are corrected for in the selected of said two signals and a formation characteristic free of barite distortion can be determined from the selected of said first signal and said first intermediate signal.