Methods and means for simultaneous casing integrity evaluation and cement inspection in a multiple-casing wellbore environment
An x-ray based cement evaluation tool for measurement of the density of material volumes within single, dual and multiple-casing wellbore environments is provided, wherein the tool uses x-rays to illuminate the formation surrounding a borehole, and a plurality of detectors are used to directly measure the density of the cement annuli and any variations in density within The tool uses x-rays to illuminate the casing surrounding a borehole and a plurality of multi-pixel imaging detectors directly measure the thickness of the casing The tool includes an internal length having a sonde section, wherein the sonde section further includes an x-ray source; a radiation shield for radiation measuring detectors; sonde-dependent electronics; and a plurality of tool logic electronics and PSUs. Other systems and subsystems appropriate for carrying out the foregoing are also disclosed, as are a plurality of example methods of use therefor.
1 . An x-ray based borehole evaluation tool comprising:
an x-ray source;
a plurality of detectors that is offset from the x-ray source in an axial direction, the plurality of detectors to measure radial density variations within a region surrounding the tool using radiant energy emitted by the x-ray source positioned within a borehole, the plurality of detectors including a first detector and a second detector positioned between the first detector and the x-ray source in the axial direction, the first detector to measure density of an annular material surrounding the borehole using the radiant energy, and the second detector to measure a thickness of a casing defining the borehole using the radiant energy; and
an actuated combination of collimators with a first collimator and a second collimator that interacts with the first collimator to control an operating mode of the tool.
2 . The tool of claim 1 , wherein axial actuation of the first collimator controls rotation of the second collimator.
3 . The tool of claim 1 , wherein rotation of the second collimator causes azimuthal rotation of the radiant energy.
4 . The tool of claim 1 , wherein rotation of the second collimator increases a resolution of azimuthal density variation measurements by the plurality of detectors relative to non-rotation of the second collimator.
5 . The tool of claim 1 , further comprising a plurality of azimuthally distributed detectors inclusive of the second detector that are coupled to the second collimator, the plurality of azimuthally distributed detectors rotatable to create multi-helical ribbon images of the casing using incoming photons that correspond to azimuthal rotation of the radiant energy.
6 . The tool of claim 1 , wherein the actuated combination of collimators comprise a square formed tube within a shielding material.
7 . The tool of claim 1 , wherein the second detector comprises a per-pixel imaging detector array to create backscatter images of the casing using incoming photons that correspond to the radiant energy.
8 . The tool of claim 7 , wherein the backscatter images comprise spectral information for photoelectric measurement of the casing.
9 . The tool of claim 1 , wherein the first detector is to measure the density of the annular material surrounding the borehole using the radiant energy and eccentricity data generated using the second detector.
10 . A method of using an x-ray based borehole evaluation tool, the method comprising:
emitting, using an x-ray source of the tool positioned within a borehole, radiant energy towards a region surrounding the tool;
causing axial actuation of a collimator of the tool to transition the tool between a first operating mode characterized by non-rotation of the radiant energy and a second operating mode characterized by azimuthal rotation of the radiant energy;
generating, by a detector array of the tool that is offset from the x-ray source in an axial direction, output data that characterizes radial density variations within the region using the radiant energy, the detector array including a first detector and a second detector positioned between the first detector and the x-ray source in the axial direction;
measuring density of an annular material surrounding the borehole in the region using a first subset of the output data generated by the first detector; and
measuring a thickness of a casing defining the borehole using a second subset of the output data generated by the second detector.
11 . The method of claim 10 , wherein the output data generated by the detector array characterizes azimuthal density variations within the region at a first resolution during the first operating mode of the tool and at a second resolution greater than the first resolution during the second operating mode of the tool.
12 . The method of claim 10 , wherein the collimator is an actuated combination of collimators with a first collimator and a second collimator surrounding the first collimator.
13 . The method of claim 12 , further comprising:
controlling azimuthal rotation of second collimator using axial actuation of the first collimator.
14 . The method of claim 12 , further comprising:
causing azimuthal rotation of the radiant energy using azimuthal rotation of the second collimator.
15 . The method of claim 10 , further comprising:
creating, by a per-pixel imaging detector array of the second detector, a backscatter image of the casing using incoming photons that correspond to the radiant energy, the backscatter image comprising spectral information for photoelectric measurement of the casing.
16 . The method of claim 15 , wherein the per-pixel imaging detector array is a single strip array that is one pixel wide and multiple pixels long, and the backscatter image is a helical ribbon image.
17 . The method of claim 16 , further comprising:
reformatting the helical ribbon image to create a 360-degree image of the casing as a function of radial depth and axial distance.
18 . The method of claim 10 , wherein measuring the density of the annular material comprises:
deconvoluting the first subset of output data using the second subset of output data for fluid compensation.