X-ray Backscatter Imaging in an Oil Well
- Melissa Spannuth (Visuray) | Morteza Esmaeili (Visuray) | Spencer Gunn (Visuray) | David M. Ponce-Marquez (Visuray) | Henning Torsteinsen (Visuray) | Adne Voll (Visuray)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 27-29 October, Amsterdam, The Netherlands
- Publication Date
- Document Type
- Conference Paper
- 2014. Society of Petroleum Engineers
- wireline, downhole imaging, well intervention, x-ray imaging, downhole video
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- 170 since 2007
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A new wireline tool that creates X-ray backscatter images of objects within a production well has been developed. Using X-rays to produce images instead of the more conventional optical video recordings offers the significant advantage that the measurement is not hindered by the nature of the production fluid. Therefore, X-ray imaging does not require the well to be specially treated in any way, saving the time and costs associated with cleaning or replacing well fluids.
The tool generates hard X-rays (>10 keV) and measures the backscattered radiation from objects and fluids directly in front of the tool using X-ray detector arrays arranged around the tool axis. Measurements of backscattered radiation are converted into three-dimensional renderings or two-dimensional images of the object using a novel fluid-based surface reconstruction technique.
Example images from operating the tool in a laboratory setting demonstrate the ability of the tool and technique to create reconstructions of objects in a variety of normal production fluids including clean water, saline water, oil, and fluids with suspended rust particles. They reveal the maximum practical imaging depth range from the bottom nose to be approximately 10 cm. The images also demonstrate the millimeter-scale resolution and accuracy of the tool.
The images were produced with a tool exhibiting a commercially viable outer diameter. Thus, this new X-ray imaging method and wireline tool can provide improved visualization and diagnostic capabilities for a significant number of offshore production wells while avoiding the expense and inconvenience of conventional imaging techniques.
When equipment becomes lost, stuck or malfunctions deep in an oil well, operators have few resources available to investigate the problem. Fishing expeditions to retrieve the equipment are time-consuming and expensive, at best, and frequently overly destructive or unsuccessful when carried out with personnel effectively blind to the downhole situation (Fowler 1996). As a result, many different tools and methods have been developed to visualize objects in a well.
The oldest method is the lead-impression block technique in which a soft block of lead is lowered to the depth of interest and deformed to the shape of the object encountered (Walker 1984). Once the block is brought back to the surface, it is inspected to provide information about the object. While this method is fast and inexpensive, the impression can often be difficult to interpret and may not provide enough information to solve the problem.
An alternate technique uses standard ultrasonic imaging (Hayman et al. 1998). This method has the advantages of providing 3D information about the structure of interest and operating in a fluid-filled well. However, it requires precise knowledge of the speed of sound in the fluid and will produce poor images when the assumed speed of sound does not match the actual speed. Furthermore, the images suffer when the fluid has too much heterogeneity (e.g. a fluid with gas bubbles or suspended solid particles). The frequent and large changes in density in such cases cause excessive absorption and scattering of the beam.
The third commonly-used downhole imaging technique is straightforward optical video (Rademaker et al. 1992). Although images or movies produced using video are easy to understand, the image quality depends greatly on the clarity of the well fluid and the ability to keep the lenses clean. Often this means that a well must be emptied of any opaque fluid and filled with clean fluid before performing optical imaging; such operations are expensive and time-consuming. Furthermore, the clean fluid must be relatively transparent to visible light, meaning that imaging cannot be performed in fluids such as drilling muds or fluids with a high concentration of suspended solid particles.
|File Size||2 MB||Number of Pages||14|