Reducing noise is paramount when doing surface microseismic monitoring as the signal-to-noise ratio is usually lower than one. In fact denoising can significantly improve results since there are many more small microseismic events rather than large ones. It is shown here that efficient denoising can be obtained during the acquisition phase by deploying the geophones into small, dense arrays called patches. The patches ensure a 20dB noise reduction in all of the directions, while the traditional radial-shaped designs suppress noise only in the inline direction. This is particularly important as many noise sources are present in the monitored area, not only at the fraccing pumps whose noise is present only on about 1% of the network. Moreover, the patches are independent arrays. This indicates that non-permit areas can easily be avoided, and also that low-noise areas can be chosen in order to deploy the patches. This, combined with their intrinsic denoising capabilities, suggests that the overall signal-tonoise ratio can be greatly enhanced.
Abstract:This report describes prototypes, measurements, and results for a project to develop a prototype pipeline in-line inspection (ILI) tool that uses electromagnetic acoustic transducers (EMATs) to detect and grade stress corrosion cracking (SCC). The introduction briefly provides motivation and describes SCC, gives some background on EMATs and guided ultrasonic waves, and reviews promising results of a previous project using EMATs for SCC.The experimental section then describes lab measurement techniques and equipment, the lab mouse and prototypes for a mule, and scan measurements made on SCC. The mouse was a moveable and compact EMAT setup. The prototypes were even more compact circuits intended to be pulled or used in an ILI tool. The purpose of the measurements was to determine the best modes, transduction, and processing to use, to characterize the transducers, and to prove EMATs and mule components could produce useful results.Next, the results section summarizes the measurements and describes the mouse scans, processing, prototype circuit operating parameters, and performance for SH0 scans. Results are given in terms of specifications -like SNR, power, insertion loss -and parametric curvessuch as signal amplitude versus magnetic bias or standoff, reflection or transmission coefficients versus crack depth. Initially, lab results indicated magnetostrictive transducers using both SH0 and SV1 modes would be worthwhile to pursue in a practical ILI system. However, work with mule components showed that SV1 would be too dispersive, so SV1 was abandoned.The results showed that reflection measurements, when normalized by the direct arrival are sensitive to and correlated with SCC. This was not true for transmission measurements. Processing yields a high data reduction, almost 60 to 1, and permits A and C scan display techniques and software already in use for pipeline inspection. An analysis of actual SH0 scan results for SCC of known dimensions showed that length and depth could be determined for deep enough cracks. Defect shadow and short length effects were apparent but may be taken into account. The SH0 scan was done with the mule prototype circuits and permanent magnet EMATs. These gave good enough results that this hardware and the processing techniques are very encouraging for use in a practical ILI tool.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.