Development of techniques for detection and dissolution enhancement of mineral deposits in petroleum pipelines using ultrasound.

Scale formation in petroleum pipelines causes progressive flow reductions, leading to large production losses and operating costs. The composition and thickness of the scale deposits vary widely, but with present technology they cannot be accurately quantified or monitored. Remedial treatments such as chemical de-scaling etc. are therefore largely based on guesswork, which can lead to expensive chemical wastage and production shutdowns. This project is intended to address some of the above problems using ultrasonic techniques. Work presented in this thesis branches out into two main areas of interest, namely: (a) developments concerning location of deposits from both top-side and down-hole locations; and (b) developments relating to enhancement of scale removal, using ultrasound. With regard to top-side scale detection, the major challenge in this work was to develop a technique by which acoustic signatures are synthetically generated, which can be used with the techniques previously developed for pipeline inspection. This required the determination of a suitable type of transducer and the study of its radiation characteristics in developing comprehensive mathematical models for artificially generating reference echoes. The model allowed the first three multiple echoes (in steel objects) to be computed for given test parameters. Close agreement of the synthesised echoes with practical measurements was demonstrated with good repeatability. An essential requirement for the detection of deposits in down-hole is the accurate alignment of the test probes with respect to the pipe-wall. In this regard, a novel technique for remote alignment of the transducers was successfully formulated. It is based on identifying symmetrical properties of the signals received from the test probe itself when scanned around the correct angular position with respect to the target. However, through extensive practical measurements, it was found that an important requirement for applying this technique is to know in advance whether a particular combination of probe, target diameter and separation distance would give satisfactory angular resolution. Extensive practical examination of these factors showed that no general conclusion can easily be drawn with respect to this requirement. Therefore a mathematical model was successfully developed, which would predict the suitability of given probe/target parameters. It has been reported in previous studies that ultrasonic irradiation could greatly enhance the chemical dissolution of localised deposits during de-scaling operations. In this regard, a major challenge was to improve the efficiency of power transducers radiating into confined spaces at elevated temperatures. That required the study of radiation characteristics of ultrasonic power transducers and compensation techniques to regain loss of efficiency at elevated temperatures. Alternative types of transducers - based on flexural-horn designs - were also investigated and their relative merits presented. Significant findings related to the performance variations of ultrasonic transducers and transmission cables at elevated temperatures have been made. After examining the transducer efficiency drop with temperature, a closed-loop compensation strategy was proposed for maintaining optimal performance. The matching requirements of the cables transmitting power from top-side to down-hole power transducers were also investigated as part of optimisation of ultrasonic power output. From this study it was found that, within the temperature range of interest, the cable in itself does not require changes to the matching requirements as the environmental temperature fluctuates. However, it was noted that the transducer impedance changes rapidly with temperature and therefore a unified compensation strategy incorporating both cable and transducer impedances was proposed as a better solution. Overall, the main objectives of the project concerning pipeline scale detection were well achieved, namely: (a) modelling of a suitable type of ultrasonic transducer to synthesise the reference multiple echoes to aid top-side scale detection; and (b) development of a remote sensing technique for ultrasonic probe alignment in downhole pipes. With regard to dissolution enhancement, techniques for enhancing power output of ultrasonic transducers to aid dissolution enhancement of scale deposits have been determined. Further work includes the improvements to software algorithms developed and hardware integration to achieve the expected performance of the techniques presented

Distributed Fiber Ultrasonic Sensor and Pattern Recognition Analytics

Ultrasound interrogation and structural health monitoring technologies have found a wide array of applications in the health care, aerospace, automobile, and energy sectors. To achieve high spatial resolution, large array electrical transducers have been used in these applications to harness sufficient data for both monitoring and diagnoses. Electronic-based sensors have been the standard technology for ultrasonic detection, which are often expensive and cumbersome for use in large scale deployments. Fiber optical sensors have advantageous characteristics of smaller cross-sectional area, humidity-resistance, immunity to electromagnetic interference, as well as compatibility with telemetry and telecommunications applications, which make them attractive alternatives for use as ultrasonic sensors. A unique trait of fiber sensors is its ability to perform distributed acoustic measurements to achieve high spatial resolution detection using a single fiber. Using ultrafast laser direct-writing techniques, nano-reflectors can be induced inside fiber cores to drastically improve the signal-to-noise ratio of distributed fiber sensors. This dissertation explores the applications of laser-fabricated nano-reflectors in optical fiber cores for both multi-point intrinsic Fabry–Perot (FP) interferometer sensors and a distributed phase-sensitive optical time-domain reflectometry (φ-OTDR) to be used in ultrasound detection. Multi-point intrinsic FP interferometer was based on swept-frequency interferometry with optoelectronic phase-locked loop that interrogated cascaded FP cavities to obtain ultrasound patterns. The ultrasound was demodulated through reassigned short time Fourier transform incorporating with maximum-energy ridges tracking. With tens of centimeters cavity length, this approach achieved 20kHz ultrasound detection that was finesse-insensitive, noise-free, high-sensitivity and multiplex-scalability. The use of φ-OTDR with enhanced Rayleigh backscattering compensated the deficiencies of low inherent signal-to-noise ratio (SNR). The dynamic strain between two adjacent nano-reflectors was extracted by using 3×3 coupler demodulation within Michelson interferometer. With an improvement of over 35 dB SNR, this was adequate for the recognition of the subtle differences in signals, such as footstep of human locomotion and abnormal acoustic echoes from pipeline corrosion. With the help of artificial intelligence in pattern recognition, high accuracy of events’ identification can be achieved in perimeter security and structural health monitoring, with further potential that can be harnessed using unsurprised learning

Passive low frequency RFID for non-destructive evaluation and monitoring

Ph. D ThesisDespite of immense research over the years, defect monitoring in harsh environmental conditions still presents notable challenges for Non-Destructive Testing and Evaluation (NDT&E) and Structural Health Monitoring (SHM). One of the substantial challenges is the inaccessibility to the metal surface due to the large stand-off distance caused by the insulation layer. The hidden nature of corrosion and defect under thick insulation in harsh environmental conditions may result in it being not noticed and ultimately leading to failures. Generally electromagnetic NDT&E techniques which are used in pipeline industries require the removal of the insulation layer or high powered expensive equipment. Along with these, other limitations in the existing techniques create opportunities for novel systems to solve the challenges caused by Corrosion under Insulation (CUI). Extending from Pulsed Eddy Current (PEC), this research proposes the development and use of passive Low Frequency (LF) RFID hardware system for the detection and monitoring of corrosion and cracks on both ferrous and non-ferrous materials at varying high temperature conditions. The passive, low cost essence of RFID makes it an enchanting technique for long term condition monitoring. The contribution of the research work can be summarised as follows: (1) implementation of novel LF RFID sensor systems and the rig platform, experimental studies validating the detection capabilities of corrosion progression samples using transient feature analysis with respect to permeability and electrical conductivity changes along with enhanced sensitivity demonstration using ferrite sheet attached to the tag; (2) defect detection using swept frequency method to study the multiple frequency behaviour and further temperature suppression using feature fusion technique; (3) inhomogeneity study on ferrous materials at varying temperature and demonstration of the potential of the RFID system; (4) use of RFID tag with ceramic filled Poly-tetra-fluoro-ethyulene (PTFE) substrate for larger applicability of the sensing system in the industry; (5) lift-off independent defect monitoring using passive sweep frequency RFID sensors and feature extraction and fusion for robustness improvement. This research concludes that passive LF RFID system can be used to detect corrosion and crack on both ferrous and non-ferrous materials and then the system can be used to compensate for temperature variation making it useful for a wider range of applications. However, significant challenges such as permanent deployment of the tags for long term monitoring at higher temperatures and much higher standoff distance, still require improvement for real-world applicability.Engineering and Physical Sciences Research Council (EPSRC) CASE, National Nuclear Laboratory (NNL)

Space benefits: The secondary application of aerospace technology in other sectors of the economy

Benefit cases of aerospace technology utilization are presented for manufacturing, transportation, utilities, and health. General, organization, geographic, and field center indexes are included

Various modulated hybrid pulse compression for advanced ultrasound technology and its non-destructive testing application

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University LondonUltrasound is a sound wave with a frequency greater than 20 kHz. It obeys the propagation laws of reflection, refraction, diffraction, and scattering. Because of its excellent physical properties, ultrasound has been used in a variety of fields, including industry and medicine. There are many techniques that use ultrasound as detection methods in the field of non-destructive testing (NDT) and medical treatment. In a typical ultrasound system, a sine wave or pulse signal with a fit window is considered as the transmitted signal. This results in low accuracy in some special situations, such as testing high attenuation material. The signal-to-noise ratio (SNR) is an important parameter for evaluating the performance of an echo signal or imaging. However, under high attenuation materials or noisy conditions, SNR will significantly decrease. Under these conditions, valid information in the received signal will be obscured by noise. This situation can cause errors in the detection system. In an ultrasound system, increasing the SNR of the echo signal can reduce detection errors and improve accuracy. First, in ultrasound systems, a noise reduction method based on pulse compression has been investigated and applied. Convolution and modulation were used in the proposed method to generate new hybrid emission signals. The hybrid codes can only be distinguished by a special matched filter that is related to the emission signals. The echo signals processed by a special matched filter have a high main lobe and a very low side lobe, implying that the side lobe level and SNR will increase. When compared to traditional denoising methods, the proposed method can significantly improve SNR while only requiring a change in the transmission code without requiring any hardware changes. Second, in a low voltage ultrasonic testing (UT) system, a hybrid phase modulated code excitation method based on the Barker and Golay code pairs was proposed and implemented. In a UT system, the lower the pulsing voltage, the lower the SNR of the signal. Attempting to reduce the pulsing voltage will result in noisy and unusable results. The proposed hybrid method can increase main lobe power in low average power transmitted and received signals. The proposed method has been theoretically examined and then tested in simulation studies. The experimental results showed that the main lobe level of the code produced by convolution of Barker code and Golay code pairs is around 30 dB higher than the simple pulse, and the main lobe of the combined code is around 15 dB higher than the traditional Barker code, with the sidelobe being the same as the Baker code that constitutes this combined code. As a result, the combined code’s peak sidelobe level (PSL) is approximately 5 dB lower than the traditional Barker code. Because of this, UT devices can be used in real-world applications, even in low-voltage situations. Third, the torsional wave mode T(0,1) hybrid phase modulated code excitation method has been proposed and applied in a long range guided wave testing (GWT) system. The proposed hybrid method combines the Barker and Golay code pair and is modulated by a fitted sine wave. This method combines the benefits of these two coding methods and increases code length flexibility. The SNR and PSL of the processed signal are used to assess the method’s performance. The proposed method has been tested in GWT using both finite element method (FEM) simulation and real-world testing. The results of pipeline laboratory testing revealed that the best increasing SNR of BCG is around 33.5 dB when compared to a simple pulse at 40 kHz, and the peak sidelobe level is around -24 dB. The proposed method, as well as other traditional methods, were used for pipeline defect detection testing. The results of the tests showed that the hybrid coded excitation method can detect notches that are difficult to detect with other methods and effectively improve the SNR. The applied method’s increasing SNR is around 6 dB, which agrees with the simulation and laboratory testing results. In UGW testing, the proposed coded excitation method was highly regarded. Finally, the non-linear frequency modulated (NLFM) hybrid pulse compression method has been proposed and implemented in an ultrasound imaging (UI) system. The proposed code combines the Barker and Golay codes and is modulated using a non-linear frequency method based on the Zak transform. Theoretical research on signal generation and decoding has been presented, as well as cyst phantom simulation. The simulation analysis shows that the novel code method can improve the contrast ratio by 15.96 dB and the SNR by 36.64 dB when compared to a simple pulse signal. Overall, this study demonstrated that the proposed novel method can be effectively used in ultrasound detection methods to improve performance