Methods and means for casing, perforation and sand-screen evaluation using backscattered x-ray radiation in a wellbore environment

Abstract

An x-ray-based cased wellbore environment imaging tool is provided, the tool including at least an x-ray source; a radiation shield to define the output form of the produced x-rays; a direction controllable two-dimensional per-pixel collimated imaging detector array; sonde-dependent electronics; and a plurality of tool logic electronics and PSUs. A method of using an x-ray-based cased wellbore environment imaging tool to monitor and determine the integrity of materials within wellbore environments is also provided, the method including at least: producing x-rays in a shaped output; measuring the intensity of backscatter x-rays returning from materials surrounding the wellbore; controlling two-dimensional per-pixel collimated imaging detector arrays; and converting image data from said detectors into consolidated images of the wellbore materials.

Claims

1. An x-ray-based cased wellbore environment imaging tool to monitor and determine the integrity of materials within wellbore environments, said tool comprising: an x-ray source; a radiation shield to define the output form of the produced x-rays into a panoramically conical shape; at least two rotatable two-dimensional per-pixel collimated imaging detector arrays; sonde-dependent electronics; and a plurality of tool logic electronics and PSUs.

2. The tool of claim 1, wherein said imaging detectors comprise two-dimensional per-pixel collimated imaging detector arrays wherein the imaging array is one pixel wide and multiple pixels long.

3. The tool of claim 1, wherein said imaging detectors further comprise two sets of two-dimensional per-pixel collimated imaging detector arrays.

4. The tool of claim 1, wherein said imaging detectors further comprise a plurality of more than two two-dimensional per-pixel collimated imaging detector arrays.

5. The tool of claim 1, wherein a rotation rate of the imaging detectors is matched to an axial logging speed of said tool so as to create a continuous helical image ribbon without blind regions.

6. The tool of claim 1, wherein the imaging detectors rotate continuously while said tool is stationary within the wellbore to produce statistically accumulated cylindrical images over the same region of the wellbore.

7. The tool of claim 1, wherein the images further comprise spectral information to inform the characteristics of any wellbore materials or debris.

8. The tool of claim 1, wherein said shield further comprises tungsten.

9. The tool of claim 1, wherein the tool is configured so as to permit through-wiring from the wireline cable head to other types of measurement tools attached to the tool string.

10. The tool of claim 1, wherein the tool is combinable with other measurement tools comprising one or more of acoustic or ultrasonic measurement tools.

11. The tool of claim 1, wherein the tool is used to determine the position, distribution and area of perforations within the casings surrounding the cased wellbore.

12. The tool of claim 1, wherein the tool is used to determine the position and integrity of sand-screens within the casings surrounding the cased wellbore.

13. The tool of claim 1, wherein the tool is used to determine the position and integrity of gravel-packs within the casings surrounding the cased wellbore.

14. The tool of claim 1, wherein the tool is used to determine the position and integrity of side-pocket mandrels within the casings surrounding the cased wellbore.

15. The tool in claim 1, wherein machine learning is employed to automatically reformat or re-tesselate images produced by the at least two imaging detector arrays as a function of depth and varying logging speeds or logging steps.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an x-ray-based casing imaging tool being deployed into a borehole via wireline conveyance. Regions of interest within the materials surrounding the borehole are also indicated.

(2) FIG. 2 illustrates one example of an x-ray-based casing imaging tool, arranged so as to enable imaging of the inner-most casing or tubing in addition to segments of the materials located outside of the casing or tubing.

BRIEF DESCRIPTION OF SEVERAL EXAMPLE EMBODIMENTS

(3) The methods and means described herein for casing integrity evaluation while simultaneously imaging equipment/features located immediately surrounding the borehole, through x-ray backscatter imaging in a cased wellbore environment, is disclosed in a package so as to not require direct physical contact with the well casings (i.e., non-padded). The methods and means disclosed herein further comprise the use of a combination of collimators, located cylindrically around an X-ray source located within a non-padded concentrically-located borehole logging tool, together with a single or plurality of rotatable two dimensional per-pixel collimated imaging detector array(s) to also be used as the primary imaging detector(s). The ability to control the viewing direction of the collimated detectors permits the operator to either log the tool through the well casing while the detectors rotated azimuthally, to produce a two dimension helical ribbon backscatter x-ray image, or to hold the tool stationary as the collimated detector rotates azimuthally to capture a cylindrical image that can be improved upon ‘statically’ (as the detector continues to recapture casing images that can be added to the existing image set), and/or to actuate the detector such that a closer inspection of a particular region may be performed by pan-tilt control of the collimated detector.

(4) In one example embodiment, an x-ray-based casing imaging tool [101] is deployed by wireline conveyance [103. 104] into a cased borehole [102], wherein the well casing or tubing [102] is imaged. The tool is enclosed by a pressure housing that ensures well fluids are maintained outside of the housing.

(5) FIG. 2 illustrates a pressure housing [201] that is conveyed through a well casing or tubing [202]. The pressure housing contains an electronic x-ray source [203] configured to produce x-rays panoramically in a conical output, the shape and distribution of said x-ray output is determined by the geometry of the collimator [204], which is formed by creating a non-blocking region of the radiation shielding. The conical x-ray beam illuminates a cylindrical section of the casing/tubing [205]. The radiation scattering from the casing is imaged by a two-dimensional detector array [208], which is attached to a per-pixel array collimator [207]. The detector collimator [207] reduces the field of view of each pixel of the detector array [208] such that each pixel images a distinct and unique section of the illuminated casing/tubing [205]. A motor/servo [209] is used to rotate the detector azimuthally, such that the collimated detector array images the illuminated ring section of the casing/tubing [205]. A further detector assembly [210] rotates upon the same armature but is geometrically configured to image a section of the wellbore that is illuminated by the x-rays but lays outside of the inner surfaces of the tubing/casing [211]. While the motor/servo [209] rotates the collimated detector arrays [207, 208, 210], back-scatter images are acquired by the detector of both the casing/tubing and the materials behind the casing/tubing. As the tool is being conveyed through the wellbore, the result is a helical ribbon of stacked images, with two distinct radial depths of investigation.

(6) In a further example embodiment, the deeper depth of radial inspection detector assemblies are used to create images of sand-screens, to aid inspection.

(7) In a further example embodiment, the deeper depth of radial inspection detector assemblies are used to create images of perforations, to aid inspection.

(8) In a further embodiment still, the deeper depth of radial inspection detector assemblies would be used to create images of gravel-packs, to aid inspection.

(9) In another embodiment, as the detector assembly rotates azimuthally, each axial ‘column’ of pixels of the detector arrays are sampled such that each column would image a similar section of the casing/tubing that had been imaged by its neighbor prior during the last sample. Upon encoding the images with the known azimuthal capture position of the image section, the separate image pixel columns associated with each imaged ‘slit’ section of the casing/tubing could be summated/averaged to produce a higher quality image within a single pass.

(10) In yet another embodiment, two detectors are used back-to-back facing outwards, or side-by-side facing opposite directions, for each detector set, such that when the detector assembly is rotated, a double-helical image ribbon is produced as the tool is conveyed through the wellbore.

(11) In another embodiment, ‘n’ detectors are used facing outwards, or arranged for maximal volumetric packing efficiency, for each detector assembly position, such that when the detector assembly is rotated, n-helical image ribbons are produced for each radial depth being images, as the tool is conveyed through the wellbore.

(12) In another embodiment, the logging speed and detector assembly rotational rate are matched such, that a single azimuthal rotation of the detector assembly is performed while the tool is conveyed axially by one imaged axial tubing/casing section [9] height, such that the resulting images of the casing/tubing, and the outer layer ‘skin’ is complete and helically welded.

(13) In a further embodiment, the detector assemblies' rotation and axial/radial tilt are controlled through the use of servos/actuators such that the operator may stop the tool within the borehole and inspect certain sections of the casing/tubing (i.e. without the detector assembly being in continual rotation mode).

(14) In a further embodiment, the operator can stop the conveyance of the tool and use the azimuthal rotation of the detector assembly to continually sample the same images tubing/casing illuminated cylinder [9] section, such that the resulting data set can build/summate statistically to improve image quality.

(15) In another embodiment, the backscatter images also comprise spectral information so that a photo-electric or characteristic-energy measurement may be taken, and the imaged material analyzed for scale-build up, casing corrosion, etc.

(16) In a further embodiment, machine learning is employed to automatically analyze the spectral (photo electric or characteristic energy) content of the images to identify key features, such as corrosion, holes, cracks, scratches, and/or scale-buildup.

(17) In a further embodiment, the per-pixel collimated imaging detector array further comprises a single ‘strip’ array (i.e., one pixel wide azimuthally) and multiple pixels long axially—the imaging result is then a ‘cylindrical’ ribbon image. When the tool is moved axially (either by wireline-winch or with a stroker, for example) and a new image set taken, a section of casing is imaged by stacking cylindrical ribbon images/logs.

(18) In a further embodiment, machine learning is employed to automatically reformat (or re-tesselate) the resulting images, as a function of depth and varying logging speeds or logging steps, such that the finalized casing and/or cement image is accurately correlated for azimuthal direction and axial depth, by comparing with CCL, wireline run-in measurements, and/or other pressure/depth data.

(19) 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.