Acoustic monitoring and mitigation of underwater construction noise was conducted during marine pier demolition and reconstruction activities near Santa Rosa Island, California. Activities spanned two construction sea...Acoustic monitoring and mitigation of underwater construction noise was conducted during marine pier demolition and reconstruction activities near Santa Rosa Island, California. Activities spanned two construction seasons and used both auger and pneumatic percussion drilling methods for pile placement. Pile drilling activities during construction resulted in sound pressure levels (SPL) ranging from 121.0 to 184.5 dB re 1 μPa. No significant difference was found for calculated source SPLs between the Season 1 and Season 2 methods of pile drilling (KW = 2.28, p = 0.15). Additionally, no significant difference was found for calculated source SPLs during active drilling between the Season 1 and Season 2 methods of pile drilling (KW = 3.39, p = 0.07). The average calculated source SPL documented during this study was lower than the NOAA Fisheries mandated safety zone threshold (160.0 dB re 1 μPa [rms]) for harassment to marine mammals. This is the first known report of SPL data collected in concert with marine pile drilling via the auger drilling technique. The results from this study can be used to improve information for and assist with the development of regulatory policies and techniques regarding sound level thresholds and mitigation monitoring.展开更多
Downhole acoustic telemetry(DAT),using a long drill string with periodical structures as the channel,is a prospective technology for improving the transmission rate of logging while drilling(LWD)data.Previous studies ...Downhole acoustic telemetry(DAT),using a long drill string with periodical structures as the channel,is a prospective technology for improving the transmission rate of logging while drilling(LWD)data.Previous studies only focused on the acoustic property of a free drill string and neglected the coupling between pipes and fluid-filled boreholes.In addition to the drill-string waves,a series of fluid waves are recorded in the DAT channel,which has not been investigated yet.Unpredictable channel characteristics result in lower transmission rates and stability than expected.Therefore,a more realistic channel model is needed considering the fluid-filled borehole.In this paper,we propose a hybrid modeling method to investigate the response characteristics of the DAT channel.By combining the axial wavenumbers and excitation functions of mode waves in radially layered LWD structures,the channel model is approximated to the 1-D propagation,which considers transmission,reflection,and interconversion of the drillstring and fluid waves.The proposed 1-D approximation has been well validated by comparing the 2-D finite-difference modeling.It is revealed that the transmitted and converted fluid waves interfere with the drill-string wave,which characterizes the DAT channel as a particular coherent multi-path channel.When a fluid-filled borehole surrounds the drill string,the channel responses exhibit considerable delay as well as strong frequency selectivity in amplitude and phase.These new findings suggest that the complexity of the channel response has been underestimated in the past,and therefore channel measurements on the ground are unreliable.To address these channel characteristics,we apply a noncoherent demodulation strategy.The transmission rate for synthetic data reaches 15 bps in a 94.5 m long channel,indicating that the acoustic telemetry is promising to break the low-speed limitation of mud-pulse telemetry.展开更多
文摘Acoustic monitoring and mitigation of underwater construction noise was conducted during marine pier demolition and reconstruction activities near Santa Rosa Island, California. Activities spanned two construction seasons and used both auger and pneumatic percussion drilling methods for pile placement. Pile drilling activities during construction resulted in sound pressure levels (SPL) ranging from 121.0 to 184.5 dB re 1 μPa. No significant difference was found for calculated source SPLs between the Season 1 and Season 2 methods of pile drilling (KW = 2.28, p = 0.15). Additionally, no significant difference was found for calculated source SPLs during active drilling between the Season 1 and Season 2 methods of pile drilling (KW = 3.39, p = 0.07). The average calculated source SPL documented during this study was lower than the NOAA Fisheries mandated safety zone threshold (160.0 dB re 1 μPa [rms]) for harassment to marine mammals. This is the first known report of SPL data collected in concert with marine pile drilling via the auger drilling technique. The results from this study can be used to improve information for and assist with the development of regulatory policies and techniques regarding sound level thresholds and mitigation monitoring.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174421 and 11734017)the Scientific Instrument Developing Project of the Chinese Academy of Sciences,China(Grant Nos.YJKYYQ20200072 and GJJSTD20210008).
文摘Downhole acoustic telemetry(DAT),using a long drill string with periodical structures as the channel,is a prospective technology for improving the transmission rate of logging while drilling(LWD)data.Previous studies only focused on the acoustic property of a free drill string and neglected the coupling between pipes and fluid-filled boreholes.In addition to the drill-string waves,a series of fluid waves are recorded in the DAT channel,which has not been investigated yet.Unpredictable channel characteristics result in lower transmission rates and stability than expected.Therefore,a more realistic channel model is needed considering the fluid-filled borehole.In this paper,we propose a hybrid modeling method to investigate the response characteristics of the DAT channel.By combining the axial wavenumbers and excitation functions of mode waves in radially layered LWD structures,the channel model is approximated to the 1-D propagation,which considers transmission,reflection,and interconversion of the drillstring and fluid waves.The proposed 1-D approximation has been well validated by comparing the 2-D finite-difference modeling.It is revealed that the transmitted and converted fluid waves interfere with the drill-string wave,which characterizes the DAT channel as a particular coherent multi-path channel.When a fluid-filled borehole surrounds the drill string,the channel responses exhibit considerable delay as well as strong frequency selectivity in amplitude and phase.These new findings suggest that the complexity of the channel response has been underestimated in the past,and therefore channel measurements on the ground are unreliable.To address these channel characteristics,we apply a noncoherent demodulation strategy.The transmission rate for synthetic data reaches 15 bps in a 94.5 m long channel,indicating that the acoustic telemetry is promising to break the low-speed limitation of mud-pulse telemetry.
