Distributed optical fiber acoustic sensor for <i>in situ</i> monitoring of marine natural gas hydrate production for the first time in the Shenhu area, China
Xiangge He, Xuemin Wu, Lei Wang, Qianyong Liang, Lijuan Gu, Fei Liu, Hailong Lu, Yi Zhang, Min Zhang, ,Guangzhou Marine Geological Survey, China Geological Survey, Ministry of Natural Resources, Guangzhou 510075, China
Abstract
The distributed acoustic sensor (DAS) uses a single optical cable as the sensing unit, which can capture the acoustic and vibration signals along the optical cable in real-time. So it is suitable for monitoring downhole production activities in the process of oil and gas development. The authors applied the DAS system in a gas production well in the South China Sea for <i>in situ</i> monitoring of the whole wellbore for the first time and obtained the distributed acoustic signals along the whole wellbore. These signals can clearly distinguish the vertical section, curve section, and horizontal production section. The collected acoustic signal with the frequency of approximately 50 Hz caused by the electric submersible pump exhibit a signal-to-noise ratio higher than 27 dB. By analyzing the acoustic signals in the production section, it can be located the layers with high gas production rates. Once an accurate physical model is built in the future, the gas production profile will be obtained. In addition, the DAS system can track the trajectory of downhole tools in the wellbore to guide the operation. Through the velocity analysis of the typical signals, the type of fluids in the wellbore can be distinguished. The successful application of the system provides a promising whole wellbore acoustic monitoring tool for the production of marine gas hydrate, with a good application prospect.