Investigation of data processing strategy for distributed optic fiber sensing and development of methods for real-time data processing

CSIRO successfully demonstrated that distributed optic fiber sensing (DOFS) technology can become a reliable and efficient tool for microseismic monitoring in longwall coal mining and have identified that a big challenge for DOFS application in coal mining is data handling. DOFS can record continuous data from thousands of channels over a 10km long fiber. Conventional microseismic data processing cannot be applied to such a big data set and a new strategy for real-time data processing and archiving must be developed before this new technology can be practically used for mining induced microseismicity monitoring.

The objective of this project was to develop a strategy to deal with the huge DOFS data set in real-time, and to develop new approaches and algorithms for rapid data processing.

Project Achievements

• A novel and robust method that uses B/W ratio on black and white images was developed for rapidly discriminating seismic events. This method achieved high levels of confidence for event identification, with 100% accuracy for strong events (magnitude greater than -1) and moderate events (magnitude ranging from -2 to -1), and 75% for weak events (magnitude below -2).
• A method that uses image edge detection was developed for determining the arrivals of the first seismic phase. Using this method, an event can be located using analytic geometry algorithms that calculate much faster than the inversion of picked arrival times.
• Based on the event locations, seismicity of the whole longwall panel and in sub-areas of the panel can be obtained. This information is very helpful to mine operators providing them with a timely assessment of the changes of ground conditions in specific locations.
• The quality of automatic data interpretation can be significantly affected by disturbances of unpredictable noise sources near some fiber sections and by poor fiber cable coupling. It was found that the best solution to address these issues is to install several fiber sections in vertical boreholes in a longwall panel.