Technology Update: New 3D Ultrasonic System Tests Pipeline Integrity
- Rienk de Vries (Applus RTD)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- December 2014
- Document Type
- Journal Paper
- 34 - 35
- 2014. Copyright is retained by the author. This document is distributed by SPE with the permission of the author. Contact the author for permission to use material from this document.
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The global oil and gas industry’s vast infrastructure includes many pipelines that were manufactured decades ago, and the intensive quality control processes in place have generally ensured that they have stood the test of time. As the technologies adopted by the industry to optimize drilling campaigns have evolved, the equipment used in the pipeline testing process has improved as well.
Nondestructive testing (NDT) is used across the industry to inspect pipelines for defects that are impossible to discover with the human eye. NDT covers a wide range of methods, such as radiography and ultrasonic testing, by which pipelines can be inspected without altering their physical properties. This allows for highly productive testing, saving time and money as well as providing valuable evaluation, troubleshooting, and research.
Ultrasonic testing makes use of sound energy to examine specific components of a pipeline, such as girth welds, thus allowing for flaw detection and sizing. The testing process is principally used to examine welds in pipelines before they are accepted for use and is vital in ensuring that the pipelines can withstand the kinds of pressures they will be subjected to in an industrial setting. Any defects in the weld could have devastating consequences for safety and the environment.
Ultrasonic inspection using the pulse echo (PE) technique or time of flight diffraction (ToFD) is widely used throughout the industry to assess weld integrity. However, quantitative defect characterization with PE remains challenging because the signal caused by the reflection at a point of defect is highly dependent on the defect’s orientation in relation to the ultrasonic beam. ToFD has sizing capabilities, when diffraction signals are present, but is limited in its ability to characterize flaws.
In phased-array inspection, the image obtained from sectorial scans cannot be directly related to the defect’s size and orientation. Data display and interpretation are not straightforward and require operator skills and experience. Ultrasonic inspection would be better and more reliable if a method would allow direct imaging of defects.
3D Ultrasonic Imaging
A recent significant advance in the field of NDT developed by Applus RTD is a 3D ultrasonic technology that uses inverse wave field extrapolation (IWEX) to enable detailed inspection and mapping of defects within critical pieces of pipework. The technology extrapolates wave field recordings back into space toward all points in the area under investigation.
If at one of those points a scatterer (e.g., a defect) is present, the backward-extrapolated wave field has high amplitude, and the resulting image will show increased intensity at that location.
If this is done for all points in the image, the location and shape of the scatterer can be determined.
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