17:15 〜 19:15
[HSC06-P05] Evaluation of the CO2 monitoring system using Distributed Acoustic Sensor at a geological storage site
キーワード：CO2地中貯留、CO2プルームのモニタリング、分布式音響計測（DAS）、地表設置回転型発振器（SOV）、繰り返し地震探査
For geological carbon storage projects, monitoring is essential to ensure that the injected CO2 has been contained in the target reservoir. For the requirements of the long-term monitoring, cost-efficient methods are preferred. Recently, a highly reliable method based on distributed acoustic sensing (DAS) has been proposed and implemented at some geological storage sites. In this paper, we investigate the detectivity of CO2 plume using DAS/VSP technique applied at the Red Trail Energy (RTE) project in North Dakota, USA, where approximately 180 kt of CO2 are storing annuary in a deep saline aquifer with the thickness of 90 m.
We firstly studied the behavior of injected CO2 in the reservoir. We developed an axisymmetric petrophysical model using well log data. Two-phase flow simulation was performed using TOUGH2. By introducing a high permeable wellbore model, we did not assume the flow rate to the formation at each well element. The simulated results suggested that, 1) CO2 was injected from the upper part of the perforation intervals, and 2) the averaged plume could be 200 m in radius and 40 m thick.
Secondly, we calculated waveform from seismic sources to confirm the difference between the baseline and the observation after CO2 injection. Data analysis followed the usual VSP data processing of the reflected wave. The results indicated that, a) a few msec of P-wave delay was observable at the near offset data, b) the effect of 100 kt of CO2 plume would be detectable from the source with 1000 m offset, and c) the difference obtained at far offsets became detectable as the radius of CO2 plume increased. The detectability of CO2 plume would be improved using the optical fiber implemented through the reservoir interval and the use of the direct wave.
These results indicate that the monitoring using SOV is suitable because the S/N of the data can be easily controlled. These evaluation procedures are helpful in developing a monitoring system at storage sites.
We firstly studied the behavior of injected CO2 in the reservoir. We developed an axisymmetric petrophysical model using well log data. Two-phase flow simulation was performed using TOUGH2. By introducing a high permeable wellbore model, we did not assume the flow rate to the formation at each well element. The simulated results suggested that, 1) CO2 was injected from the upper part of the perforation intervals, and 2) the averaged plume could be 200 m in radius and 40 m thick.
Secondly, we calculated waveform from seismic sources to confirm the difference between the baseline and the observation after CO2 injection. Data analysis followed the usual VSP data processing of the reflected wave. The results indicated that, a) a few msec of P-wave delay was observable at the near offset data, b) the effect of 100 kt of CO2 plume would be detectable from the source with 1000 m offset, and c) the difference obtained at far offsets became detectable as the radius of CO2 plume increased. The detectability of CO2 plume would be improved using the optical fiber implemented through the reservoir interval and the use of the direct wave.
These results indicate that the monitoring using SOV is suitable because the S/N of the data can be easily controlled. These evaluation procedures are helpful in developing a monitoring system at storage sites.