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Distributed Fiber-Optic Magnetic Sensing for Subsurface Imaging and Monitoring

Description: 

Distributed fiber-optic sensing (DFOS) technology offers a cost-effective, versatile solution for geophysical applications, with advantages such as extended sensing range, high spatial resolution, durability, and flexibility. While electromagnetic (EM) sensing holds promise for improving fluid saturation mapping to complement seismic imaging and monitoring, distributed EM sensing systems are still in early development stages. This study introduces an optical-fiber-based distributed magnetic sensing (DMS) system, simultaneously recording acoustic and magnetic wavefields. The DMS system uses a standard distributed acoustic sensing (DAS) interrogator, probing a specialized single-mode fiber optic cable embedded with magnetostrictive wires. These wires, responding to EM fields, induce strain in the fiber core in addition to mechanical strains detected by standard single mode fiber. By measuring backscattered light, the strain-induced phase variation between two sensing fiber segments is detected. In validation experiments, prototype DMS fibers, with and without fiber Bragg gratings (FBGs), exhibited expected spectral responses to controlled EM and acoustic sources, consistent with theoretical predictions. The DMS system achieved sub-millitesla (mT) magnetic field intensity resolution over a bandwidth of 10-2000 Hz. Cross-well EM time-lapse simulation and inversion of CO₂ injection demonstrated the proposed DMS system's potential sensitivity, highlighting its potential to augment seismic monitoring in realistic scenarios. Preliminary results showcase valuable insights into this multi-physics optic sensing system, indicating its potential for monitoring subsurface fluid changes. These findings set the stage for further research and development of an integrated DAS and DMS system, enabling more comprehensive and cost-effective geophysical applications.

Session: Advancing Seismology with Distributed Fiber Optic Sensing [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Shihao

Student Presenter: No

Invited Presentation: 

Authors