Claims
- 1. A logging tool for measuring a property of material penetrated by a borehole, comprising:
(a) a nuclear radiation detector comprising alternating components of scintillating material and non scintillating, hydrogenous, optically transparent material, wherein said components are fabricated to optimize detector response; (b) means cooperative with said detector to generate a signal indicative of radiation impinging upon said detector; and (c) means for transforming said signal into a measure of said property.
- 2. The logging tool of claim 1 wherein said components are cylindrical.
- 3. The logging tool of claim 1 wherein said components are panels.
- 4. The logging tool of claim 1 wherein said components comprise:
(a) a plurality of axially parallel cylinders distributed within a bounding axially parallel cylinder; and (b) said scintillating material alternates with said non scintillating, hydrogeneous, optically transparent material at each interface of said components.
- 5. The logging tool of claim 1 wherein geometric configuration and dimensions of said components are selected to optimize total detector efficiency response.
- 6. The logging tool of claim 1 wherein geometric configuration and dimensions of said components are selected to optimize detector spectroscopy efficiency response.
- 7. The logging tool of claim 1 wherein said scintillating material is ZnS.
- 8. The logging tool of claim 1 wherein said non scintillating, hydrogenous, optically transparent material is plastic.
- 9. A logging tool for investigating a parameter of material penetrated by a borehole, comprising:
(a) a detector comprising ZnS and contained within a pressure housing; (b) means cooperating with said detector to generate a signal indicative of radiation impinging upon detector; and (c) means for relating said signal to said parameter.
- 10. The logging tool of claim 9 wherein said pressure housing is conveyed along said borehole by means of a wireline.
- 11. The logging tool of claim 9 wherein said pressure housing is conveyed along said borehole by means of a drill string.
- 12. A logging system comprising:
(a) a borehole instrument comprising
(i) a fast neutron source, and (ii) a fast neutron detector axially spaced from said fast neutron source, wherein (b) said fast neutron detector comprises at least one interface between hydrogen rich and optically transparent material and material which scintillates when irradiated with protons, and wherein (c) the geometric configuration and dimensions said hydrogen rich and optically transparent material and said material which scintillates are selected for a predetermined detector diameter thereby geometrically optimizing the detector efficiency for fast neutrons.
- 13. The logging system of claim 12 wherein said neutron source emits repetitive bursts of fast neutrons into earth formation, and said tool further comprises:
(a) a first gamma ray detector axially spaced from said neutron source at a first spacing to measure
(i) prompt gamma radiation during said bursts of fast neutrons, and (ii) gamma radiation induced by fast neutrons interacting with nuclei within said earth formation; (b) a second gamma ray detector axially spaced from said neutron source at a second spacing to measure
(i) prompt gamma radiation during said bursts of fast neutrons, and (ii) gamma radiation induced by said fast neutrons interacting with nuclei within said earth formation; and wherein (c) said fast neutron detector measures fast neutrons resulting from interaction of said fast neutrons with nuclei within said formation.
- 14. The logging system of claim 12 wherein said material which scintillates is ZnS.
- 15. The logging system of claim 12 wherein hydrogen rich and optically transparent material is plastic.
- 16. The logging system of claim 13 further comprising data analysis means for combining said measures of prompt gamma radiation and said measure of fast neutrons to obtain measures of at least one parameter of interest of said earth formation.
- 17. The logging system of claim 16 wherein said at least one parameter comprises gas saturation.
- 18. The logging system of claim 16 wherein said at least one parameter comprises porosity.
- 19. The logging system of claim 16 wherein said at least one parameter comprises bulk density.
- 20. The logging system of claim 13 wherein said second spacing is greater than said first spacing.
- 21. A method for measuring at least one parameter of a material, the method comprising:
(a) irradiating said material with high energy neutrons; (b) measuring fast neutrons resulting from interaction of said high energy neutrons with said material using a geometrically optimized ZnS/plastic fast neutron detector; (c) using said measure of fast neutrons to determine said parameter of said material.
- 22. The method of claim 21 comprising the additional step of measuring prompt gamma radiation resulting from inelastic scatter of said high energy neutrons within said material and combining with said measure of fast neutrons to determine said parameter of said material.
- 23. The method of claim 21 wherein said material comprises the environs of a borehole penetrating earth formation.
- 24. The method of claim 23 wherein said formation is irradiated with pulses of high energy neutrons produced by a neutron generator.
- 25. The method of claim 24 farther comprising:
(a) providing a first axially spaced gamma ray detector within said borehole at a first spacing from said neutron generator and providing a second axially spaced gamma ray detector at a second spacing from said neutron generator; (b) measuring said prompt gamma radiation at said first and said second spacings with said gamma ray detectors; (c) axially spacing within said borehole said geometrically optimized ZnS/plastic fast neutron detector at a third spacing from said neutron source; and (d) measuring said fast neutrons at said third spacing with said geometrically optimized ZnS/plastic fast neutron detector.
- 26. The method of claim 25 wherein said second spacing and said third spacing are greater than said first spacing.
- 27. The method of claim 25 further comprising the steps of:
(a) measuring said fast neutrons at a high energy level and at a low energy level at said third spacing with said geometrically optimized ZnS/plastic fast neutron detector; and (b) combining said fast neutron high energy measurement and said fast neutron low energy measurement to minimize effects of said borehole upon said determination of said parameter of said earth formation.
- 28. The method of claim 25 wherein said gamma ray measurements and said fast neutron measurements at said high energy level and said low energy level are made during said neutron pulses.
- 29. The method of claim 25 wherein said at least one parameter comprises gas saturation.
- 30. The method of claim 25 wherein said at least one parameter comprises porosity.
- 31. The method of claim 25 wherein said at least one parameter comprises bulk density.
- 32. The method of claim 21 comprising the additional step of energy discriminating a response of said geometrically optimized ZnS/plastic fast neutron detector so that said detector responds only to fast neutrons impinging thereon.
- 33. A method for measuring a property of material penetrated by a borehole, comprising:
(a) placing a nuclear radiation detector within said material, wherein
(i) said detector comprises alternating components of scintillating, material and non scintillating, hydrogenous, optically transparent material, and (ii) said components are dimensioned to optimize detector efficiency; (b) providing means cooperative with said detector to generate a signal indicative of radiation impinging upon said detector; and (c) providing means for transforming said signal into a measure of said property.
- 34. The method of claim 33 wherein said components are cylindrical.
- 35. The method of claim 33 wherein said components are panels.
- 36. The method of claim 33 wherein said components comprise:
(a) a plurality of axially parallel cylinders distributed within a bounding axially parallel cylinder thereby forming interfaces; and (b) said scintillating material alternates with said non scintillating, hydrogeneous, optically transparent material at each said interfaces.
- 37. The method of claim 33 comprising the additional step of selecting geometric configuration and dimensions of said components to optimize total detector efficiency for a specified detector diameter.
- 38. The method of claim 33 comprising the additional step of selecting geometric configuration and dimensions of said components to optimize spectroscopy efficiency of the detector for a specified detector diameter.
- 39. The method of claim 33 wherein said scintillating material is ZnS.
- 40. The method of claim 33 wherein said non scintillating, hydrogenous, optically transparent material is plastic.
- 41. A method for investigating a parameter of material penetrated by a borehole, comprising:
(a) mounting a detector comprising ZnS within a pressure housing; and (b) generating a signal from an output of said detector which is indicative of radiation impinging upon detector and thereby indicative of said parameter.
- 42. The method of claim 41 comprising the additional step of conveying said pressure housing along said borehole by means of a wireline.
- 43. The method of claim 41 comprising the additional step of conveying said pressure housing along said borehole by means of a drill string.
RELATED APPLICATIONS
[0001] This application is related to application Ser. No. ______entitled “Geometrically Optimized Fast Neutron Detector” and application Ser. No. ______entitled “Geometrically Optimized Fast Neutron Detector”.