Back to results
US 2011/0297818 A1Published application
Neutron-generator-based thermal neutron porosity device with high porosity sensitivity
AssigneeSchlumberger Technology Corporation
InventorJames L. Thornton
Life of this patent
Estimating the term…
Abstract
Systems, methods, and devices for determining porosity with high sensitivity are provided. In one example, a downhole tool with such high porosity sensitivity may include a neutron source, a near neutron detector, and a far neutron detector. The neutron source may emit neutrons into the subterranean formation, which may scatter and be detected by the near and far detectors. The near neutron detector may be disposed near enough to the neutron source to detect a maximum number of neutrons when the porosity of the subterranean formation is greater than 0 p.u.
Claims23
A downhole tool comprising:
- a neutron source configured to emit neutrons into a subterranean formation having a porosity;
- a near neutron detector configured to detect neutrons scattered by the subterranean formation, wherein the near neutron detector is disposed near enough to the neutron source to detect a maximum number of neutrons when the porosity of the subterranean formation is greater than 0 p.u.;
- and
- a far neutron detector configured to detect neutrons scattered from the subterranean formation, wherein the far neutron detector is disposed a greater distance from the neutron source than the near neutron detector.
1 more element
A downhole tool comprising:
- an electronic neutron generator;
- and
- a thermal neutron detector having an active region, wherein a face of the active region nearest to the electronic neutron generator is disposed less than approximately 10 inches from the electronic neutron generator.
A method comprising:
- lowering a downhole tool into a subterranean formation having a porosity;
- emitting neutrons from a neutron source of the downhole tool into the subterranean formation;
- detecting counts of neutrons scattered by the subterranean formation using a near neutron detector and a far neutron detector of the downhole tool, wherein the far neutron detector is located further from the neutron source than the near neutron detector and the near neutron detector is located near enough to the neutron source to detect a maximum number of neutrons when the porosity of the subterranean formation is greater than 0 p.u.;
- and
- determining a property of the subterranean formation, using data processing circuitry configured to receive the counts of the neutrons detected by the near neutron detector and the far neutron detector, based at least in part on the counts of the neutrons.
2 more elements
A system comprising:
- a downhole tool having a neutron source configured to emit neutrons of higher average energy than an AmBe neutron source into a subterranean formation and a near neutron detector and a far neutron detector configured to detect counts of thermal neutrons that have been scattered by the subterranean formation, wherein the near neutron detector is disposed nearer to the neutron generator than the far neutron detector, and wherein the near neutron detector is disposed a distance from the neutron source such that, when the downhole tool is placed in the subterranean formation via an 8-inch fresh-water-filled borehole and when the subterranean formation comprises a calcite formation having fresh-water-filled porosity at 20° C. and 1 atm, the near neutron detector detects fewer thermal neutrons at a porosity of 0 p.u. than at a higher porosity;
- and
- data processing circuitry configured to determine a porosity of the subterranean formation based at least in part on a ratio of a count of thermal neutrons detected by the near neutron detector to a count of thermal neutrons detected by the far neutron detector.
A downhole neutron porosity tool comprising:
- a neutron source configured to emit neutrons into a subterranean formation;
- a near neutron detector configured to detect neutrons scattered from the subterranean formation, wherein a face nearest to the neutron source of an active region of the near neutron source is disposed at a first distance from the neutron source, wherein the first distance is selected such that the near neutron detector detects a maximum number of neutrons when the subterranean formation has a first porosity and a minimum number of neutrons when the subterranean formation has a second porosity, wherein the minimum number of neutrons is more than 50% of the maximum number of neutrons;
- and
- a far neutron detector configured to detect neutrons scattered from the subterranean formation, wherein a face nearest to the neutron source of an active region of the far neutron detector is at a second distance from the neutron source, wherein the second distance is greater than the first distance.
1 more element
Dependencies are inferred from the claim text.