9:45 AM - 10:00 AM
[STT35-04] Rapid Progress of Seismic Monitoring System using Optical Fiber and DAS Technology
Keywords:DAS, hDVS, optical fiber, seismic monitoring, earthquake, tsunami
With the recent development of the Internet and mobile technology, the processing power of various consumer computers, especially data servers, and the capacity to hold data have been remarkably improved. Today, online conferences and lessons are becoming routine tasks, accelerating further advances in data servers. The rapid development of such technology also benefits seismic observations with new methods.
DAS (Distributed Acoustic Sensing) technology, which observes seismic waves using a long-range optical fiber as a distributed vibration sensor, began to be used in the oil and gas industry as a new geophysical exploration technology from around 2011. “heterodyne Distributed Vibration Sensing” (hDVS), which uses backscattered light with improved linearity, began to be used around 2014 1). At the 2017 JpGU-AGU Meeting, we announced the third generation hDVS system completed in the latter half of 2016 2). Compared to the second generation system, the S/N ratio of the data was improved and the data processing capacity was also improved, but the achievement was that the Optical Interrogator in the optical circuit section and the Processing Server in the data processing section were clearly separated, so that it was rationalization efforts. The performance improvement due to this was about double. At the time of 2016, the maximum capacity of one SATA or SAS type 3.5-inch HDD that can be purchased in general was 4TB, and the maximum capacity when eight units were configured in RAID 1 was 16TB. At that time, this amount of data storage was sufficient to record VSP continuously for several days. However, in recent years, the capacity of 16 TB has not been sufficient for one month of continuous recording using a long-distance optical fiber exceeding 10 km.
The clear separation of the optical circuit section and the data processing section, which is the main feature of the third-generation system, made the subsequent development aimed at improving performance relatively easy. The optical circuit section is equivalent to a so-called analog circuit, and its performance can only be improved by improving the coherency and stability of the laser module, speeding up the optical modulation, and improving the optical fiber technology, but the development speed is slow due to unique technology. On the other hand, the data processing unit corresponding to a digital circuit, that is, the server, is not much different from a general-purpose Internet-related server, and is expected to have a rapid improvement in performance due to the demand of high-speed data handlings.
hDVS Tier-3+ is a device that improves only the server part of the third generation system, the data processing capacity is improved by about 4 times, and the maximum capacity of data retention can be increased by 4 times with the advent of large capacity HDD. In other words, we were able to achieve a four-fold improvement in performance in four years. Due to this performance improvement, when the optical pulse rate is set to 1 kHz (1 ms sampling), the performance that can be recorded using a fiber with a length of 100 km can be achieved, which is the theoretical limit of the DAS device. An actual optical fiber has an optical loss, and in the case of a general communication fiber, the typical value of the loss is around 0.2 dB/km. Since the total optical loss that can be handled by current DAS equipment is about 10 dB, the actual limit is about 50 km.
The main improvements of hDVS Tier-3+ are shown below.
a)Achieved the maximum optical limit of about 50 km of the current optical fiber in DAS observation.
b)Observations up to 100 km are possible if the loss of optical fiber can be further reduced.
c)In addition to the standard mode (minimum gauge length 5m), a high-resolution mode has been added (minimum gauge length 1.5m).
d)The gauge length can be set as a parameter with many options from 1.5m to 300m.
e)4 types of high-pass filters can be selected and data in the low frequency range including 0.01Hz can be acquired.
f)By improving the data processing capacity, a higher optical pulse rate can be set and the S/N ratio of the data has improved.
g)Output in HDF5 format is possible in addition to SEGY.
h)Observation is possible at a maximum optical pulse rate of 20 kHz (sampling is possible at a minimum of 0.05 ms).
i)Improved reliability of hDVS Server and reduced noise.
With the advent of hDVS Tier-3 +, it has become possible to make more expansive observations that take advantage of DAS.
References:
1) Hartog, A. et al, The Optics of Distributed Vibration Sensing, 2nd EAGE Workshop on Permanent Reservoir Monitoring, July 2-5, 2013
2) Kimura, T., Progress of Seismic Monitoring System using Optical Fiber and DAS Technology, JpGU-AGU 2017 STT59-04
DAS (Distributed Acoustic Sensing) technology, which observes seismic waves using a long-range optical fiber as a distributed vibration sensor, began to be used in the oil and gas industry as a new geophysical exploration technology from around 2011. “heterodyne Distributed Vibration Sensing” (hDVS), which uses backscattered light with improved linearity, began to be used around 2014 1). At the 2017 JpGU-AGU Meeting, we announced the third generation hDVS system completed in the latter half of 2016 2). Compared to the second generation system, the S/N ratio of the data was improved and the data processing capacity was also improved, but the achievement was that the Optical Interrogator in the optical circuit section and the Processing Server in the data processing section were clearly separated, so that it was rationalization efforts. The performance improvement due to this was about double. At the time of 2016, the maximum capacity of one SATA or SAS type 3.5-inch HDD that can be purchased in general was 4TB, and the maximum capacity when eight units were configured in RAID 1 was 16TB. At that time, this amount of data storage was sufficient to record VSP continuously for several days. However, in recent years, the capacity of 16 TB has not been sufficient for one month of continuous recording using a long-distance optical fiber exceeding 10 km.
The clear separation of the optical circuit section and the data processing section, which is the main feature of the third-generation system, made the subsequent development aimed at improving performance relatively easy. The optical circuit section is equivalent to a so-called analog circuit, and its performance can only be improved by improving the coherency and stability of the laser module, speeding up the optical modulation, and improving the optical fiber technology, but the development speed is slow due to unique technology. On the other hand, the data processing unit corresponding to a digital circuit, that is, the server, is not much different from a general-purpose Internet-related server, and is expected to have a rapid improvement in performance due to the demand of high-speed data handlings.
hDVS Tier-3+ is a device that improves only the server part of the third generation system, the data processing capacity is improved by about 4 times, and the maximum capacity of data retention can be increased by 4 times with the advent of large capacity HDD. In other words, we were able to achieve a four-fold improvement in performance in four years. Due to this performance improvement, when the optical pulse rate is set to 1 kHz (1 ms sampling), the performance that can be recorded using a fiber with a length of 100 km can be achieved, which is the theoretical limit of the DAS device. An actual optical fiber has an optical loss, and in the case of a general communication fiber, the typical value of the loss is around 0.2 dB/km. Since the total optical loss that can be handled by current DAS equipment is about 10 dB, the actual limit is about 50 km.
The main improvements of hDVS Tier-3+ are shown below.
a)Achieved the maximum optical limit of about 50 km of the current optical fiber in DAS observation.
b)Observations up to 100 km are possible if the loss of optical fiber can be further reduced.
c)In addition to the standard mode (minimum gauge length 5m), a high-resolution mode has been added (minimum gauge length 1.5m).
d)The gauge length can be set as a parameter with many options from 1.5m to 300m.
e)4 types of high-pass filters can be selected and data in the low frequency range including 0.01Hz can be acquired.
f)By improving the data processing capacity, a higher optical pulse rate can be set and the S/N ratio of the data has improved.
g)Output in HDF5 format is possible in addition to SEGY.
h)Observation is possible at a maximum optical pulse rate of 20 kHz (sampling is possible at a minimum of 0.05 ms).
i)Improved reliability of hDVS Server and reduced noise.
With the advent of hDVS Tier-3 +, it has become possible to make more expansive observations that take advantage of DAS.
References:
1) Hartog, A. et al, The Optics of Distributed Vibration Sensing, 2nd EAGE Workshop on Permanent Reservoir Monitoring, July 2-5, 2013
2) Kimura, T., Progress of Seismic Monitoring System using Optical Fiber and DAS Technology, JpGU-AGU 2017 STT59-04