Safe Large Scale Underground Hydrogen Storage Achieved By Optical Sensor Array Monitoring

To demonstrate Intrinsically Safe, Optical Multi-Sensor-Array Based, Monitoring Technologies to safeguard Underground Gas Storage (UGS) Paulsson, Inc. (Paulsson) partnered with Pacific Gas & Electric (PG&E) and California Energy Commission (CEC) in 2021 to research, design, manufacture, deploy, and field-operate a robust, large-aperture, cost-effective, and all-optical UGS reservoir surveying and monitoring system. During the 3-year project Enhanced Distributed Acoustic Sensor (EDAS) and Distributed Temperature Sensor (DTS) data have been recorded, at a rate of 2TB per day, processed, and analyzed on a 24/7 basis in real-time. Paulsson and PG&E installed the optical sensor system and it has been on-line since November 2021. The system is comprised of 2,600 Acoustic Sensors (EDAS) and 1,600 Temperature Sensors (DTS), tubing deployed in a 5,500ft deviated well servicing a large UGS field in central California near Sacramento. The primary objectives of the project are to determine and demonstrate the capabilities and reliability of fiber optic multi-sensor array technologies for monitoring gas-field wellbores and UGS reservoirs. The optical sensor system is recording the acoustic and temperature data from UGS operations, including gas injection, withdrawal, and formation gas flows in real time. The sensor array also recorded the impact on the UGS reservoir from many earthquakes, small, large, local, and distant. The earthquakes have provided valuable seismic source data that we used for site characterization. The results of this UGS monitoring project are discussed and its implications for safeguarding Underground Hydrogen Storage in all concentrations including mixed with Natural Gas at 20% as a first step.