For the safe and sustainable use of deep geothermal wells, construction must proceed as intended. An integer well ensures that all fluids within the borehole are always under control. One of the most critical steps is the cementing of the casings. Despite extensive experience in the petroleum industry, challenges with well integrity are a worldwide phenomenon. One reason could be that conventional measurement methods can only verify the success of cementing once the cement job has been completed. In contrast, distributed fiber optic sensing methods can monitor the entire cementing process along the entire drilling path.
This data set contains the results of the Distributed Temperature Sensing (DTS) and the derived product "vibrational energy" of a Distributed Dynamic Strain Sensing (DDSS or DAS) of the whole cementing process. We collected this data during the primary cementing of an injection well's 874m surface casing at the geothermal site Schäftlarnstr, Munich. We measured the cement placement and 24 hours of the early hydration.
We obtained the data with a fiber optic cable permanently deployed behind the casing. The cable contained Multi-Mode fibers (for DTS) and Single-Mode fibers (for DAS). Table 1 in the data description document shows the units used and the key parameters of our measurement.
In the first step, we allocated each channel to its depth in the borehole. We used a cold spray (for DTS) and a tap test (for DAS) to locate the entry to the borehole. To obtain the vibrational energy of the DAS data, we summarized the raw dynamic strain with a Root Mean Square (RMS) in a window of 60 seconds. We calculated the vibrational energy for a wide range of different frequency ranges (Butterworth bandpass). The data are provided in csv formats and further explained in the data description document.
Acknowledgement:
GFK-Monitor is funded by the Federal Ministry for Economic Affairs and Climate Action via the Project Management Jülich (PTJ) (funding code: 03EE4036, project duration: July 1, 2022 - June 30, 2025). The fiber optic infrastructure was provided by GAB (Geothermie Allianz Bayern): Funded by: Bayerisches Staatsministerium für Wissenschaft und Kunst (Hauptgebäude: Salvatorstraße 2, 80333 München).
The GFZ-Landsvirkjun Theistareykir Fibre array is located in the Theytareykir geothermal area, in North Iceland. It is collocated with arrays of broadband seismometers and gravity meters (see e.g., https://doi.org/10.1186/s40517-021-00208-w). The geometry of the fibre array is following the telecom network in the area, and was chosen to test the seismological capabilities of telecom cables in this geothermal environment. We connected an iDAS V2 interrogator from Silixa. The interrogator location is lat=65.898041, lon=-16.966274.
The array starts N-S and after 1.5 km, turns towards the East, up to a local transmission antenna station for mobile phones. The length of the path is ~5 km. The length of the cable is actually more than 15 km, as other fibre instance is connected at the transmission antenna station.. Jumps were performed along the cable to geo-locate the channels. The exact location of the fibre can unfortunately not be disclosed. Original recordings at 1000 Hz were downsampled to 200 Hz using a software from INGV-OE (michele.prestifilippo@ingv.it) and are provided in an h5 format. We provide here the first fibre instance (5 km long).
The data contain 1 h long recording intervals framing M>5 teleseismic earthquakes recorded in the frame of the global DAS month, an initiative to collaboratively record and share simultaneously recorded DAS data from all over the world (https://www.norsar.no/in-focus/global-das-monitoring-month-february-2023). DAS is an emerging technology increasingly used by seismologists to convert kilometer long optical fibers into seismic sensors.
The here referenced dataset provides eventbased Distributed Acoustic Sensing (DAS) recordings made with an approximately 22 km long dark telecommunication fiber lying in urban Potsdam and surroundings. For each of 164 M>=5 earthquakes occurring in February 2023 and listed by the USGS, one hour of data is provided starting with the event's origin time. Additionally, the whole day of February 14 is provided in hourly files.
The data was recorded in the frame of the global DAS month, an initiative to collaboratively record and share simultaneously recorded DAS data from all over the world (https://www.norsar.no/in-focus/global-das-monitoring-month-february-2023). DAS is an emerging technology increasingly used by seismologists to convert kilometer long optical fibers into seismic sensors.