Methods and Means for Identifying Fluid Type Inside a Conduit

Abstract

An x-ray-based borehole fluid evaluation tool for evaluating the characteristics of a fluid located external to said tool in a borehole using x-ray backscatter imaging is disclosed, the tool including at least an x-ray source; a radiation shield to define the output faun of the produced x-rays into the borehole fluid outside of the tool housing; at least one collimated imaging detector to record x-ray backscatter images; sonde-dependent electronics; and a plurality of tool logic electronics and power supply units. A method of using an x-ray-based borehole fluid evaluation tool to evaluate the characteristics of a fluid through x-ray backscatter imaging is also disclosed, the method including at least producing x-rays in a shaped output; measuring the intensity of backscatter x-rays returning from the fluid to each pixel of one or more array imaging detectors; and converting intensity data from said pixels into characteristics of the wellbore fluids.

Claims

1. An x-ray-based borehole fluid evaluation tool for evaluating the characteristics of a fluid located external to said tool in a borehole using x-ray backscatter imaging, wherein said tool comprises: an x-ray source; a radiation shield to define the output form of the produced x-rays into the borehole fluid outside of the tool housing; at least one collimated imaging detector to record x-ray backscatter images; 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 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 comprises a two-dimensional pinhole-collimated imaging detector array, wherein the imaging array is multiple pixels wide and multiple pixels long.

4. The tool of claim 1, wherein said collimated imaging detector collects information regarding backscattered x-ray energy.

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

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

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

8. The tool of claim 1, further comprising a means of conveyance to convey the tool through the borehole.

9. The tool of claim 8, further comprising a depth logging device to log the depth of the tool as it is conveyed through the borehole.

10. The tool of claim 9, further comprising a depth correlation system to correlate said x-ray backscatter images with the depth at which the images were acquired.

11. The tool of claim 1, wherein said tool logic electronics further comprise a means to sum groups of pixels from said at least one imaging detector.

12. The tool of claim 1, further comprising an automated computational x-ray backscatter image conversion system to convert said x-ray backscatter images to fluid characteristics.

13. The tool of claim 4, further comprising an automated x-ray backscatter energy conversion system to convert said x-ray backscatter energy information to fluid characteristics.

14. A method of using an x-ray-based borehole fluid evaluation tool to evaluate the characteristics of a fluid through x-ray backscatter imaging, said method comprising: producing x-rays in a shaped output; measuring the intensity of backscatter x-rays returning from the fluid to each pixel of one or more array imaging detectors; and converting intensity data from said pixels into characteristics of the wellbore fluids.

15. The method of claim 14, further comprising measuring the energy of backscatter x-rays returning from the fluid and converting said energy data into characteristics of the wellbore fluids.

16. The method of claim 14, further comprising measuring the energy of backscattered X-rays returning from the fluid and converting said energy into characteristics of any wellbore materials or debris.

17. The method of claim 14, further comprising measuring the intensity of backscatter-xrays returning from the fluid to one or more subsets of pixels on one or more array imaging detectors.

18. The method of claim 17, further comprising summing the individual intensity measurements of one or more subsets of pixels comprising groups of pixels.

19. The method of claim 14, further comprising combining other measurement methods comprising one or more of acoustic, ultrasonic, neutron, electromagnetic and/or other x-ray-based methods.

20. The method of claim 14, wherein said characteristics of a fluid comprise one or more of: the composition of said fluid, the density of said fluid, or the water cut of said fluid.

21. The method of claim 14, further comprising continuously conveying said x-ray based borehole fluid evaluation tool through a borehole; recording the depth of said tool versus time; periodically measuring one or more of the intensity and energy of backscatter x-rays returning from the fluid; correlating the periodic backscatter x-ray measurements with depth; and converting each of the depth-correlated periodic x-ray backscatter measurements into characteristics of a fluid to create a log of fluid characteristics versus depth.

22. The method of claim 14, further comprising conveying said x-ray based borehole fluid evaluation tool to one or more pre-determined depths in a borehole; measuring one or more of the intensity and energy of backscatter x-rays returning from the fluid at each pre-determined depth; recording the depth of said tool at each measurement point; correlating the backscatter x-ray measurements with depth; and converting each of depth-correlated x-ray backscatter measurements into characteristics of fluid to create a log fluid characteristics versus depth.

23. The method of claim 14, further comprising using automated computations to convert backscatter X-ray energy information into fluid characteristics.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 depicts a first embodiment comprising a tool [101] disposed within a fluid [105,109] filled conduit [100] containing an x-ray source [102] which is illuminating a volume of fluid [105,109] separated by a fluid interface [108] with x-rays [104]. The scattered radiation resulting from the x-rays interaction with the fluid [105] located in front of the tool is collected by a detector array [103] or arrays.

[0031] FIG. 2 depicts the same embodiment, however the notion that the tool has moved further into the conduit is illustrated by the movement of the fluid interface [202] into the fluid annulus between the tool and the conduit wall, consequently the scattering response of the fluid [201] will be different to the response of the interface between the two fluids in front of the tool.

DETAILED DESCRIPTION OF SEVERAL EXAMPLE EMBODIMENTS

[0032] There are no previously known technologies available on the market capable of providing an operator with non-disruptive means for determining the composition of a fluid or location of a fluid interface within a borehole with any significant level of detail with respect to the precise depth of a fluid interface or change.

[0033] The invention described and claimed herein therefore comprises a method and means for permitting an operator to determine the precise depth location and characteristic of a fluid in a conduit through a forward-looking fluid analysis method that does not seek to remove a sample of fluid from the wellbore into the apparatus, so that the fluid remains undisturbed and outside of the apparatus during measurement particularly in a region in front of the apparatus as it is lowered in to the conduit.

[0034] The objects of the invention are achieved by acquiring radiation backscattered from fluids disposed in front of the tool in the area of the conduit that has not been disturbed by the action of the measurement. The backscattered radiation is to be collected by detector arrays and analyzed in detail using computational comparative characterization techniques.

[0035] In the first embodiment, primary x-rays [104] are produced by and x-ray tube [102] located within a pressure resistance tool housing [101]. The primary x-rays illuminate a section of the well fluids [105, 109] in front of the tool [101] and results in the backscattering of radiation from both the Thompson and Compton effects. The scattered radiation [106] enters a collimation device [107] such as a pinhole, optical slot, array collimator or other collimation means, such as an array collimator, and falls upon a detector array [103] or arrays. The scattered radiation [106] is distributed across the surface of the detector array [103] which may consist of a linear array or an area array.

[0036] Compared to a detector based upon a single scintillator crystal- and photomultiplier tube, a pixel array effectively consists of many individual detectors, and as the nature of a collimator will always reduce the number of incoming counts compared to no collimation, it can be envisioned that a pixel array will have a number of key benefits. Firstly, by distributing the total collected number of counts over a number of pixels, the statistical noise associated with each pixel can be reduced when the all of the counts associated with all of the detectors is combined as a single reading. An idealized detector would be capable of producing noise statistics identical to Poissonian distribution, however, by increasing the number of individual detectors measuring an acquisition, it is possible to reduce the overall signal to noise ratio within acceptable standards when considering the short acquisition times required to capture a reasonable data rate when considering that the tool is moving through the fluid and through the conduit. Once all of the individual counts associated with each pixel of each detector has been summed, it can be assumed that the statistical noise has been reduced to such an extent that the useable signal to noise ratio is sufficient to determine changes in the overall acquisitioned count rate such that a sufficient (such as <1%) change in fluid response would be detectable.

[0037] As the backscatter response of the fluid can be shown to be independent of the density of the fluid to the lowest order, it is possible to create a characteristic response of each of the fluid types that one would expect to encounter in a fluid filled conduit. In that respect, the measured fluid response can be compared against a database of known fluid responses and the fluid type determined as a function of the depth of the tool as it is moved through the conduit.

[0038] In a further embodiment, the tool is stationary and the fluid type is determined as a function of depth, using a combination of casing collar locators and run in depth of the wireline without requiring the tool to be moving through the conduit.

[0039] In a further embodiment, the detector is a scintillator crystal which is coupled to a photo multiplier tube or photodiode.

[0040] In a further embodiment, the primary radiation [104] is produced by a chemical ionizing radiation source, such as a radioisotope.

[0041] In a further embodiment, the counts from each pixel of the detector array are not summed to obtain the total counts incident upon the entire detector, but instead individual pixels or groups of pixels are analyzed. This embodiment capitalizes on the highly localized region of space interrogated by each pixel in order to provide information about the spatial variations in fluid properties across the conduit. Furthermore, the scattered radiation recorded by different pixels or groups of pixels represents scattering through different angles as well as different attenuation path lengths. By comparing the signals received by different pixels with respect to these differences in scattering geometry, additional information can be obtained that may improve the fluid identification.

[0042] The foregoing specification is provided for illustrative purposes only, and is not intended to describe all possible aspects of the present invention. Moreover, while the invention has been shown and described in detail with respect to several exemplary embodiments, those of skill in the pertinent arts will appreciate that minor changes to the description and various other modifications, omissions and additions may be made without departing from the scope thereof.