WO2019171082A1

WO2019171082A1 - Downhole inspection apparatus and method

Info

Publication number: WO2019171082A1
Application number: PCT/GB2019/050660
Authority: WO
Inventors: Christopher Scott; Jonathan Thursby
Original assignee: E. V. Offshore Limited
Priority date: 2018-03-08
Filing date: 2019-03-08
Publication date: 2019-09-12

Abstract

Inspection systems and inspection methods for inspecting downhole surfaces are disclosed. An inspection system comprises an inspection tool having an imaging device for capturing images of the downhole surface, and a projection device for projecting a pre-determined pattern of laser light from the tool onto the downhole surface such that at least a part of the projected pattern lies in a field of view of the imaging device. Preferably, the inspection tool also comprises the projection device. The projected pattern in the image may be analysed to determine geometrical information about the imaged area of the downhole surface.

Description

DOWNHOLE INSPECTION APPARATUS AND METHOD

FIELD OF THE INVENTION

This invention relates to apparatus, systems and methods for inspecting a downhole surface or structure such as a pipe or conduit. In particular, but not exclusively, the invention relates to a system and method for creating a 3D model of the interior surface of a pipe or conduit, such as a wellbore conduit or downhole casing, by optical inspection, and to apparatus and methods providing improved imaging of downhole features in turbid fluids.

BACKGROUND TO THE INVENTION

Several tools have been developed for capturing images of the surface of a downhole pipe or conduit. A downhole inspection tool typically includes one or more cameras arranged to capture images of the surface. It is often desirable to capture a full 360° view of the surface, although in some cases it can be sufficient to capture a narrower angle of view.

One type of inspection tool includes a camera positioned at an end or tip of the tool. The field of view of the camera comprises a region ahead of the tool and includes a view of the internal surface of the pipe or conduit at a distance from the end of the tool. This arrangement is known as a downview camera. In such cases, a 360° view can be captured by using a camera with a suitably wide field of view.

A second type of inspection tool includes a single, sideview camera that is mounted to view a region of the internal surface of the pipe located radially outwardly of the inspection tool. In order to obtain a 360° view, the camera can be rotated about an axis of the tool to capture a series of images that are then processed and stitched together to create a full 360° image.

A third type of inspection tool utilises a plurality of cameras located around the circumference of the tool. The camera positions and the angle of view of each of the cameras may be selected such that the cameras are able to cover a full 360° view of the internal surface of the pipe or conduit. The images captured by each of the cameras are then processed and stitched together to create the full 360° view.

In each of these cases, the images obtained can be useful in identifying and assessing features of interest during inspection of the pipe or conduit. Such features of interest may include areas of corrosion or erosion, deposits, obstructions, wear, buckling, perforations, sleeve or screen damage, other damage and areas where milling, cutting, clean-up and similar operations have been performed.

One disadvantage of the use of such images for inspection is that three- dimensional data is not readily discernible from the images. Three-dimensional data is useful in a number of circumstances, for example to determine the depth of corrosion pits, the shape of a buckled or distorted area, the size of an obstruction, and so on.

A further problem is that images obtained from optical inspection systems can be distorted due to lens effects and the refractive index of the fluid within the conduit.

Another disadvantage in optical inspection systems is that the image quality can be significantly degraded when the pipe or conduit contains a fluid, in particular an opaque, cloudy or turbid fluid.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide apparatus and methods for obtaining information about the three-dimensional geometry of an imaged region during optical inspection of a pipe or conduit. Embodiments of the invention enable three-dimensional geometry information to be obtained even when image quality is affected by a downhole fluid.

In a first aspect of the invention, an inspection system for inspecting a downhole surface is provided. The system comprises an inspection tool having an imaging device for capturing images of the downhole surface, and a projection device for projecting a pre-determined pattern of laser light from the tool onto the downhole surface such that at least a part of the projected pattern lies in a field of view of the imaging device.

The resulting image, including the projected pattern, can be analysed to extract geometrical information about the imaged area. The downhole surface may, for example, comprise an internal surface of a conduit, such as a pipe, wellbore, cased hole, uncased hole and so on.

Preferably, the inspection tool comprises the projection device. Accordingly, in an embodiment, a downhole inspection tool comprises an imaging device, such as a camera, and a projection device or laser projector.

The pre-determined pattern of laser light may comprise a plurality of nodes arranged in an array or mesh pattern. For example, the pattern may comprise an array of dots, with each dot comprising a node of the array or pattern. Other pre determined patterns, such as grids, line patterns and so on may be used. For example, the pattern may comprise a grid of lines, in which case each node of the array may comprise an intersection between perpendicular lines of the grid. Preferably, if projected onto a planar surface, the nodes, dots or other features of the array or pattern would be equally spaced.

Preferably, the angular distribution of nodes, dots or other features in the projected pattern with respect to a perspective centre is pre-determined.

The perspective centre may lie at a fixed position with respect to an axis of the inspection tool and may be offset from an image plane (focal plane) of the imaging device. The perspective centre preferably lies on a projection axis of the projection device. The projection axis may be non-parallel to an optical axis of the imaging device. Known relationships between the optical axis and focal point of the camera and the perspective centre and reference (projection) axis allow analysis of the imaged projected pattern.

The inspection system may further comprise an analysis module including a processor. The analysis module may be configured to obtain, from the imaging device, an image of the downhole surface including at least a part of the projected image, and analyse the projected pattern in the image to determine geometrical information about the imaged area of the downhole surface. Preferably, the analysis module is configured to determine a three-dimensional shape of at least a part of the imaged area of the downhole surface. The analysis module may be housed in or otherwise associated with the inspection tool, or alternatively the analysis module may be disposed remotely from the inspection tool, such as at the surface, and connected to the inspection tool through a suitable data connection.

In a second aspect, the invention resides in a method of inspecting a downhole surface, comprising projecting a pre-determined pattern of laser light onto the downhole surface, obtaining an image of the downhole surface including at least a part of the projected pattern, and analysing the projected pattern in the image to determine geometrical information about the imaged area of the downhole surface.

The geometrical information may comprise a three-dimensional shape of at least a part of the imaged area of the downhole surface. The geometrical information may, alternatively or in addition, comprise a distance between the inspection tool and the imaged area of the downhole surface.

The method may comprise projecting the pattern of laser light from an inspection tool. The image of the downhole surface may be obtained using an imaging device of the inspection tool. The method may comprise projecting the laser light towards the downhole surface through a downhole fluid.

The pre-determined pattern may comprise a plurality of nodes arranged in an array. Preferably, the angular distribution of nodes with respect to a perspective centre of the projected pattern is pre-determined. The method may comprise identifying the positions of the nodes in the image, and determining, from the positions of the nodes and the pre-determined angular distribution of the nodes, a distance between the inspection tool and one or more regions of the surface in the image.

The position of the nodes, dots or other features in the imaged pattern may be used together with a known angular distribution of the nodes to estimate the distance between the tool and an area of the image. By determining the estimated distance between the tool and a plurality of regions of the image, the three- dimensional shape of the imaged area can be approximated. Known photogrammetry analysis techniques may be employed.

Accordingly, the method may comprise determining, from the positions of the nodes and the pre-determined angular distribution of the nodes, the distance between the inspection tool and a plurality of regions of the surface in the image to estimate a three-dimensional shape of the part of the imaged area of the surface.

In an embodiment, the projected pattern in the image may be analysed using pattern-matching and/or pattern-recognition image analysis tools to identify one or more features of interest of the surface in an image.

In an embodiment, the perspective distortion of the imaged projected pattern may be normalised before subsequent processing.

The downhole surface may comprise an internal surface of a conduit. The method may comprise using the determined distance to determine an offset or eccentricity between an axis of the inspection tool and a central axis of the conduit.

Because the pattern is projected in laser light, good penetration through opaque, turbid or cloudy fluids can be achieved with minimum scattering. In this way, the projected pattern may remain visible in images obtained from the imaging device even when other details are obscured by the presence of the fluid. In this way, the three-dimensional shape of the imaged area can still be estimated. This would not be possible with conventional LED illumination of the imaged area.

The images obtained in the systems and methods of the invention may be analysed in real-time or may be post-processed.

The images may be obtained by an imaging device comprising a camera that is configured to obtain still images. Alternatively, or in addition, the camera may be configured to obtain video images.

The field of view of the imaging device, and the field of projection of the projection device, may be 360°. In this case, when used to inspect an internal surface of a pipe or conduit, the three-dimensional shape of the whole circumference of the pipe or conduit can be determined from a single image. In other cases, the field of view of the or each imaging device and/or the field of projection of the projection device is less than 360°. In these cases, the three-dimensional shape of the whole circumference of a pipe or conduit can be determined if desired by combining data from a plurality of images.

The imaging device may for example be a downview camera, a sideview camera or multiple sideview cameras. A plurality of cameras and/or a plurality of laser projectors may be provided, in any combination. For example, one projector may project a pattern into the areas imaged by a plurality of cameras, or one camera may image an area into which overlapping or non-overlapping patterns are projected from a plurality of projectors. Preferably, the or each camera has an associated projector.

In another embodiment, a method of optically inspecting a downhole surface comprises projecting a pattern of laser light towards the downhole surface; obtaining an image of the downhole surface; and analysing the imaged projected pattern to determine a three-dimensional geometry of the surface. Preferably, the method comprises projecting the laser light from a downhole tool, and obtaining an image of the downhole surface using a camera of the downhole tool. The method may comprise projecting the laser light towards the downhole surface through a downhole fluid.

The three-dimensional data in combination with the image data may be used for monitoring and assessment of corrosion or erosion, for the monitoring and assessment of deposits or obstructions, for the monitoring of the integrity (e.g. shape and size) of perforations, and for the observation and examination of milling or clean-up operations. The system and method may be used to assist in processes for cutting or punching or perforating downhole hardware, in processes for the placement of abrasive or chemical cleaning agents, in processes for the removal of foreign objects, and for the monitoring of production or leaks. Additionally, it is envisaged that the system and method may also be used for blowout preventer (BOP) inspection, subsurface safety valve (SSSV) inspection, sliding sleeve or inflow control device (ICD) inspection, lock profile inspection, plug / packer / valve removal, or sand control inspection.

Preferred and/or optional features of each aspect and embodiment of the invention described above may also be used, alone or in appropriate combination, in the other aspects and embodiments also.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which like reference signs are used for like features, and in which:

Figures 1 a and 1 b show downhole tools according to the invention, in use in a downhole environment;

Figure 2 is a schematic diagram illustrating imaging of a pattern projected onto a non-planar surface; Figure 3 is a schematic diagram illustrating homography mapping;

Figure 4a is an image obtained from a downview downhole camera in a high- turbidity fluid without a projected laser pattern, and Figure 4b is a corresponding image with a projected laser pattern;

Figure 5 is an image obtained from a sideview downhole camera with a projected laser pattern, showing perforations in the imaged conduit;

Figure 6 is an image obtained from a sideview downhole camera disposed eccentrically with respect to the axis of the conduit; and

Figure 7 illustrates a method for determining geometrical information.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Referring to Figure 1 a, in an embodiment of the invention a downhole inspection tool 10 comprises an imaging device in the form of a downview camera 12 at its lowermost end. A lighting arrangement 14 is disposed adjacent and above the camera 12. The tool 10 is disposed in a conduit 100 having an internal surface 102.

The lighting arrangement 14 includes a plurality of light sources arranged for area illumination of a part of the conduit surface 102 beyond the lowermost end of the tool 10. The camera 12 is arranged so that the field of view of the camera 12 includes or lies within the illuminated area.

A projection device comprising a laser pattern projector 16 is mounted in the lighting arrangement 14. The laser pattern projector 16 projects a grid array of dots 18 onto the conduit surface 102, in the illuminated area. Each dot 18 provides a node of the array.

The pattern of dots 18 is therefore visible in images captured by the camera 12. The laser pattern projector 16 may comprise a laser diode and a diffraction grating or diffraction grid (also known as a diffuser) that splits the beam from the laser diode into multiple beams to form the dots 18. Although only one laser pattern projector 16 is shown in the tool 10 of Figure 1 , it will be appreciated that two or more projectors could be included to increase the area over which the pattern is projected.

Figure 1 b shows a variant of the tool 20 that includes a sideview camera 22 in addition to the downview camera 12. A lighting arrangement 24 including a one or more light sources is provided to illuminate at least part of the field of view of the sideview camera 22. A second laser pattern projector 26 is mounted in the lighting arrangement 24, and is arranged to project a second grid array of dots 28 onto the conduit surface 102 in the field of view of the sideview camera 22.

In a further variant (not shown), the downview camera and associated lighting arrangement and laser pattern projector is omitted.

Figure 2 illustrates how the invention can be used to determine the three- dimensional shape of a contoured surface, such as the wall 102 of the conduit 100. Figure 2 shows, schematically, the projection of a pattern (in this case a regular grid) from a perspective centre 200 (corresponding to the diffraction grating of the laser pattern projector 16) onto a contoured surface 202. When the surface 202 is imaged, a distorted pattern 204 is visible on the image plane 206. Since the geometry of the projected pattern is known, the three-dimensional shape of the contoured surface 202 can be determined from analysis of the distorted pattern 204 using known photogrammetry techniques.

It will be appreciated that the imaged area of the wall 102 will typically be viewed at an angle to the perpendicular to the surface, particularly in a downview camera arrangement. Accordingly, the imaged pattern will include a perspective distortion. Figure 3 illustrates how homography mapping can be used to correct for perspective distortion. In Figure 3, a point X on plane P corresponds to point X’ on plane p, where planes P and p are non-parallel. Plane P may represent a nominal surface onto which a pattern is projected and plane p may represent an image plane. The relationship between the coordinates xi, yi of point X and the coordinates ¾, y2 of point X’ are given by

where H is the homographic transformation matrix. H can be derived from knowledge of the projected pattern geometry, allowing correction for perspective distortion, lens distortion, refractive index distortion and eccentricity of the tool.

Using these techniques, the three dimensional geometry of the conduit surface 102 can be reconstructed from the obtained images. In one example, a method for analysing the images obtained from the camera 12, 22 comprises (1 ) normalising the perspective distortion of the grid; (2) calculating the tool eccentricity; and (3) reconstructing the three-dimensional geometry.

The perspective centre 200 of the pattern is preferably at a fixed position with respect to the longitudinal axis of the inspection tool 10, 20. In this way, the offsets between the perspective centre 200 of each projected pattern and the focal point of the respective camera 12, 22 are known. In most arrangements, the perspective centre 200 is offset from an image plane of the respective camera 12, 22, although in some cases the projector and the camera could be integrated in such a way that the perspective centre 200 lies on the image plane of the camera 12, 22.

The pattern is projected from the perspective centre 200 along a projection axis of the projector. The projection axis is for example defined by the perspective centre 200 and a geometrically central point of the pattern (when projected onto a planar perpendicular surface), such that both the perspective centre 200 and the central point of the pattern lie on the projection axis. The projection axis is preferably not parallel to the optical axis of the corresponding camera.

Figures 4a and 4b show images taken with the downview camera of a tool of the type shown in Figure 1 a when in use to image the internal surface of a conduit in which a turbid fluid is present. Figure 4a shows an image obtained by the camera with the laser pattern projector switched off. The image has been enhanced with image processing as known in the art. Even so, it is difficult to determine the shape of the internal surface from the image.

Figure 4b shows an image obtained with the laser pattern projector switched on. The laser pattern is projected towards the conduit surface on the right hand side of the image. The laser light penetrates the fluid with little scattering so that the pattern can be clearly seen in the image. In this way, the shape of the conduit surface is clearly visible. The above-described image processing techniques can be used to calculate the three-dimensional geometry of the surface to a high degree of accuracy if desired.

Figures 5 and 6 show images taken with a tool having a sideview camera and a laser pattern projector, as illustrated in Figure 1 b, when in use to image the internal surface of a conduit in which a turbid fluid is present.

Figure 5 shows an image in which the surface in the field of view includes perforations, one of which is wholly within the area onto which the laser pattern is projected. This perforation can be clearly seen, whereas those perforations that are outside the projected pattern area are more obscure.

Figure 6 shows an image taken with the tool in an off-centre position. The spacing of the dots of the pattern can be used to determine the eccentricity in the position of the tool.

In all of Figures 4a to 6, the projected pattern extends over only part of the field of view of the camera. In other arrangements, the projected pattern may extend across the whole of the field of view of the camera.

In the embodiments of Figures 1 a and 1 b, the laser pattern projectors 16, 26 are arranged to project the pattern away from the longitudinal axes of the conduit and the tool, towards the internal side surface 102 of the conduit 100, to allow enhanced imaging of the surface 102. The present invention can also be applied in a forward-facing configuration, so that the laser pattern is projected downhole of the tool, generally parallel to or along the longitudinal axes of the tool and the conduit, with the camera being arranged to image a corresponding downhole area. This configuration can be useful in fishing operations. In some embodiments, the tool includes a first laser projector arranged to project a first laser pattern towards the side surface 102 of the conduit and a second laser projector arranged to project a second laser pattern generally along the longitudinal axis of the conduit.

In alternative arrangements (not illustrated), the projection device may be mounted on a separate tool or device that may be coupled to or deployed together with the inspection tool in which the imaging device is housed.

The inspection tool may include an analysis module configured to handle the processing steps necessary to obtain images and analyse the projected patterns in those images to determine the geometrical information about the imaged surface. The analysis module may include, for example, a processor, one or more data storage devices, one or more interfaces, and/or other suitable features that will be familiar to those skilled in the art.

In an alternative arrangement, the analysis module may be disposed separately from the inspection tool, for example in a surface module. Communication between the inspection tool and the analysis module may be through any suitable means, for example through a cable linking the inspection tool and the analysis module or a wireless data transmission arrangement. Where the analysis module is configured to receive image data directly from the or each camera of the inspection tool, the analysis can be performed in or close to real-time. It is also possible that the analysis module may be configured to post process the image data from the inspection tool. In this case, the analysis module need not be in direct communication with the inspection tool, but could instead be embodied as a separate unit. The analysis module could for example comprise a general purpose computer programmed with suitable software.

Figure 7 provides a summary of the methods described above for inspecting a downhole surface.

In step 301 , a pre-determined pattern of laser light is projected onto the surface. In step 302, an image of the surface is obtained. The image includes at least a part of the projected pattern. In step 303, the projected pattern in the image is analysed to determine geometrical information about the imaged area of the surface.

Further modifications and variations not explicitly described herein can also be contemplated without departing from the scope of the invention as defined in the appended claims.

Claims

1. An inspection system for inspecting a downhole surface, comprising:

an inspection tool having an imaging device for capturing images of the downhole surface; and

a projection device for projecting a pre-determined pattern of laser light from the tool onto the downhole surface such that at least a part of the projected pattern lies in a field of view of the imaging device.

2. The inspection system of Claim 1 , wherein the inspection tool comprises the projection device.

3. The inspection system of Claim 1 or Claim 2, wherein the pre-determined pattern comprises a plurality of nodes arranged in an array.

4. The inspection system of Claim 3, wherein the pattern comprises an array of dots, and wherein each node of the array comprises a dot.

5. The inspection system of Claim 3, wherein the pattern comprises a grid of lines, and wherein each node of the array comprises an intersection between perpendicular lines of the grid.

6. The inspection system of any of Claims 3 to 5, wherein, when projected onto a planar surface, the nodes of the array are equally spaced.

7. The inspection system of any of Claims 3 to 6, wherein the angular distribution of the nodes with respect to a perspective centre of the projected pattern is pre-determined.

8. The inspection system of Claim 7, wherein the perspective centre of the projected pattern is at a fixed position with respect to an axis of the inspection tool.

9. The inspection system of Claim 8, wherein the perspective centre of the projected pattern is offset from an image plane of the imaging device.

10. The inspection system of any of Claims 7 to 9, wherein the perspective centre of the projected pattern lies on a projection axis of the projection device.

11. The inspection system of Claim 10, wherein the projection axis is non parallel to an optical axis of the imaging device.

12. The inspection system of any preceding claim, wherein the imaging device comprises a downview camera.

13. The inspection system of any preceding claim, wherein the imaging device comprises one or more sideview cameras.

14. The inspection system of any preceding claim, further comprising an analysis module including a processor, the analysis module being configured to:

obtain, from the imaging device, an image of the downhole surface including at least a part of the projected image; and

analyse the projected pattern in the image to determine geometrical information about the imaged area of the downhole surface.

15. The inspection system of Claim 14, wherein the analysis module is configured to determine a three-dimensional shape of at least a part of the imaged area of the downhole surface.

16. A method of inspecting a downhole surface, comprising:

projecting a pre-determined pattern of laser light onto the downhole surface; obtaining an image of the downhole surface including at least a part of the projected pattern; and

analysing the projected pattern in the image to determine geometrical information about the imaged area of the downhole surface.

17. A method according to Claim 16, wherein the geometrical information comprises a three-dimensional shape of at least a part of the imaged area of the downhole surface.

18. A method according to Claim 16 or Claim 17, comprising projecting the pattern of laser light from an inspection tool.

19. A method according to any of Claims 16 to 18, comprising obtaining the image of the downhole surface using an imaging device of the inspection tool.

20. A method according to any of Claims 16 to 19, comprising projecting the laser light towards the downhole surface through a downhole fluid.

21. A method according to any of Claims 16 to 20, wherein the pre-determined pattern comprises a plurality of nodes arranged in an array, and wherein the angular distribution of nodes with respect to a perspective centre of the projected pattern is pre-determined.

22. A method according to Claim 21 , comprising:

identifying the positions of the nodes in the image; and determining, from the positions of the nodes and the pre-determined angular distribution of the nodes, a distance between the inspection tool and one or more regions of the surface in the image.

23. A method according to Claim 21 when dependent on Claim 17, comprising:

determining, from the positions of the nodes and the pre-determined angular distribution of the nodes, the distance between the inspection tool and a plurality of regions of the surface in the image to estimate a three- dimensional shape of the part of the imaged area of the surface.

24. A method according to Claim 22 or Claim 23, wherein the surface comprises an internal surface of a conduit, and wherein the method comprises using the determined distance to determine an offset between an axis of the inspection tool and a central axis of the conduit.

25. A method according to any of Claims 16 to 24, comprising analysing the projected pattern in the image using pattern-matching and/or pattern- recognition to identify one or more features of interest of the surface.

26. A method according to any of Claims 16 to 25, comprising normalising a perspective distortion of the projected pattern before analysing the projected pattern.