Methods and Means for Neutron Imaging Within a Borehole

Abstract

A borehole neutron imaging tool having a two-dimensional array of neutron detector crystals, wherein said tool includes at least a source of neutrons; at least one collimated imaging detector to record images created by incident neutrons; sonde-dependent electronics; and a plurality of tool logic electronics and power supply units. A method for borehole neutron imaging, the method including controlling the direction of incident neutrons onto the imaging array; imaging said borehole surroundings; and creating a composite image of the materials surrounding the formation.

Claims

1. A borehole neutron imaging tool having a two-dimensional array of neutron detector crystals, wherein said tool comprises: a source of neutrons; at least one collimated imaging detector to record images created by incident neutrons; sonde-dependent electronics; and a plurality of tool logic electronics and power supply units.

2. The tool of claim 1, wherein said collimated imaging detector further comprises a two-dimensional per-pixel collimated imaging detector array wherein the imaging array is multiple pixels wide and multiple pixels long.

3. The tool of claim 1, wherein said collimated imaging detector further comprises a plurality of two-dimensional per-pixel collimated imaging detector arrays wherein the imaging arrays are multiple pixels wide and multiple pixels long.

4. The tool of claim 1, wherein said collimated imaging detector further comprises a two-dimensional per-pixel collimated imaging detector array wherein the imaging array is multiple pixels wide and a single pixel long.

5. The tool of claim 1, wherein said collimated imaging detector collects energy information about the detected photons.

6. The tool of claim 1, wherein said collimated image neutron information is processed to analyze the content to determine the porosity of materials surrounding the borehole.

7. The tool of claim 1, wherein said collimated image neutron information is processed by use of machine learning to analyze the content to determine the material composition of materials surrounding the borehole.

8. The tool of claim 1, wherein said tool is configured so as to permit through-wiring.

9. The tool of claim 1, wherein said tool is combined with one or more other measurement tools comprising one or more of acoustic, ultrasonic, electromagnetic and/or other x-ray-based tools.

10. A method for borehole neutron imaging, wherein said method comprises: controlling the direction of incident neutrons onto the imaging array; imaging said borehole surroundings; and creating a composite image of the materials surrounding the formation.

11. The method of claim 10, further comprising processing said collimated image energy information in order to analyze the spectral content to determine the material porosity.

12. The method of claim 10, further comprising processing said collimated image energy information by use of machine learning to analyze the spectral content to determine the material composition.

13. The method of claim 10, wherein said method is combined with one or more other measurement tools comprising one or more of acoustic, ultrasonic, electromagnetic and/or other x-ray-based tools.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 illustrates a neutron imaging tool being lowered into a well by means of wireline conveyance, in addition to the fractures surrounding the cased wellbore.

[0029] FIG. 2 illustrates one example of an arrangement of an arrayed neutron imaging detector using an arrangement of square pixels.

[0030] FIG. 3 illustrates one example of an arrangement of an arrayed neutron imaging detector using an arrangement of round pixels.

[0031] FIG. 4 illustrates one example of an arrangement of an arrayed neutron imaging detector wherein the individual pixels are arrayed to form a hemispherical dragon-fly eye format.

[0032] FIG. 5 illustrates one example of an arrangement of an arrayed neutron imaging detector using an arrangement of square pixels.

BRIEF DESCRIPTION OF SEVERAL EXAMPLE EMBODIMENTS

[0033] The invention described herein comprises both methods and means for enabling a wireline operator to evaluate the homogeneity of cement behind casing through azimuthal neutron porosity imaging in pursuit of determining cement integrity and zonal isolation. The method and means also permits for the evaluation of cement behind casing when the wireline tool is located within tubing inside of casing which is cemented. This is especially useful when considering plug and abandonment operations where it would be highly advantageous to be able to determine to quality of the zonal isolation and integrity of the cement being the casing prior to removal of the tubing. The method and means also permits for azimuthal information to be attained during logging of open-hole environments which would be of particular value when determining fracture efficiencies and fracture biases in the formation after fracking operations have been performed. This disclosure does not limit the possibility of combining the package with other forms of cement characterization, such as acoustic or x-ray, nor combinability of the means with other types of well logging methods.

[0034] In one embodiment (and with reference now to FIG. 1), a neutron porosity imaging logging tool [101] is accompanied by an x-ray cement evaluation and/or acoustic imaging tool [102] by wireline conveyance [103] into a cased borehole, wherein the cemented section of the well [104] is logged through the inner-most casing or tubing [105].

[0035] The tool [101] houses a neutron source that emits neutrons into the materials surrounding the wellbore. A detector array [206], or a plurality of detector arrays, or an azimuthally distributed plurality of detector arrays are set do look radially outward into the materials surrounding the wellbore.

[0036] FIG. 2 illustrates how an array of individual square-formed (Lithium-6) Li6-doped glass or Li6I crystals [201] are located within a matrix of material [202] with a very high neutron capture cross-section, such as Boron-10 or Cadmium, to form collimation for the incident neutron directionality. The matrix is optically coupled to a scintillator [203] such as Cadmium Telluride, Cadmium Zinc Telluride, Sodium Iodide, Cesium Iodide or Lanthanum Bromide, which is additionally bonded to a CMOS or CCD array [204].

[0037] In a further embodiment, an additional Gadolinium [205] ‘layer’ can be used around the collimated shield matrix to convert epithermal neutrons into thermal neutrons.

[0038] FIG. 3 illustrates how an array of individual cylindrically-formed [306] (Lithium-6) Li6-doped glass or Li6I crystals [301] are located within a matrix of material [302] with a very high neutron capture cross-section, such as Boron-10 or Cadmium, to form collimation for the incident neutron directionality. The matrix is optically coupled to a scintillator [303] such as Cadmium Telluride, Cadmium Zinc Telluride, Sodium Iodide, Cesium Iodide or Lanthanum Bromide, which is additional bonded to a CMOS or CCD array [304].

[0039] In a further embodiment, an additional Gadolinium [305] ‘layer’ can be used around the collimated shield matrix to convert epithermal neutrons into thermal neutrons.

[0040] FIG. 4 illustrates how an array of individual Li6-doped glass or Li6I crystals [401] are distributed in an azimuthally aligned arrangement and located within a matrix of material [402] with a very high neutron capture cross-section, such as Boron-10 or Cadmium, to form collimation for the neutron directionality. The matrix is optically coupled to a scintillator [403] such as Cadmium Telluride, Cadmium Zinc Telluride, Sodium Iodide, Cesium Iodide or Lanthanum Bromide, which is additional bonded to a CMOS or CCD array [404].

[0041] In a further embodiment, an additional Gadolinium [405] ‘layer’ can be used around the collimated shield matrix to convert epithermal neutrons into thermal neutrons.

[0042] FIG. 5 illustrates how an array of individually-formed [502] (Lithium-6) Li6-doped glass or Li6I crystals are located within a matrix of material [503] with a very high neutron capture cross-section, such as Boron-10 or Cadmium, to form collimation for the incident neutron directionality. The matrix is optically coupled to a scintillator [504] such as Cadmium Telluride, Cadmium Zinc Telluride, Sodium Iodide, Cesium Iodide or Lanthanum Bromide, which is additional bonded to a CMOS or CCD array [505]. The shielding material [503] may be extended beyond the surface of the Li6 arrays [502] such that the collimator ratio is increased, and the solid-angle of neutron detection decreased—thereby increasing the positional resolution of the origin of the incoming neutron.

[0043] In a further embodiment, an additional Gadolinium [501] ‘layer’ can be used around the collimated shield matrix to convert epithermal neutrons into thermal neutrons.

[0044] In a further embodiment, six detector arrays are assembled into a cube shape, such that the detector assemble can be used to determine the general direction (in 3D space) from which the neutron arrived.

[0045] In an alternative embodiment, the square-formed Li6-doped glass or Li6I crystals could be replaced with cylindrical Li6-doped glass or Li6I crystals.

[0046] In a further embodiment, an array of individual Li6-doped glass or Li6I crystals are distributed in an azimuthal arrangement and located within a matrix of material with a very high neutron capture cross-section, such as Boron-10 or Cadmium, to form collimation for the neutron directionality. The matrix is optically coupled to a scintillator such as Cadmium Telluride, Cadmium Zinc Telluride, Sodium Iodide, Cesium Iodide or Lanthanum Bromide, which is additional bonded to a CMOS or CCD array. An additional Gadolinium ‘wrap’ can be used around the collimated shield matrix to convert epithermal neutrons into thermal neutrons.

[0047] In a further embodiment, the detectors can be manipulated by actuators such that the operator can adjust the directionality of the array. In an alternative form of the embodiment, an array or plurality of arrays can be rotated around the central axis of the tool, such that a spiral imaging log or cylindrical imaging log of the wellbore surroundings can be created.

[0048] In a further embodiment, the tool can be placed within a LWD string to produce azimuthal images of the formation in real-time, such that the directional-drilling head can be directed toward higher-porosity regions.

[0049] In a further embodiment, the output signal from either a proportion or all of the pixels may be combined for the purposes of improving or modifying the statistical analysis of the measured neutrons.

[0050] In a further embodiment, the output signal from either a proportion or all of the pixels may be displayed as a physical two-dimensional image of neutron intensity at the detector.

[0051] In a further embodiment, the shielding material may be removed such that the crystal array is contiguous.

[0052] In a further embodiment, the output of the imaging array is used to determine the porosity of materials surrounding the borehole.

[0053] In a further embodiment, the output of the imaging array is processing using machine learning, such that the energy and distribution of the detected neutrons may be used to determine the distribution and type of materials surrounding the borehole.

[0054] In a further embodiment, the neutron imaging tool, can be combined with x-ray, and/or acoustic tools.

[0055] The foregoing specification is provided only for illustrative purposes, and is not intended to describe all possible aspects of the present invention. While the invention has herein been shown and described in detail with respect to several exemplary embodiments, those of ordinary skill in the art will appreciate that minor changes to the description, and various other modifications, omissions and additions may also be made without departing from the spirit or scope thereof.