Distributed Fiber Optic Arrays: Integrated Temperature and Seismic Sensing for Detection of CO 2 Flow, Leakage and Subsurface Distribution

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1 Distributed Fiber Optic Arrays: Integrated Temperature and Seismic Sensing for Detection of CO 2 Flow, Leakage and Subsurface Distribution Robert C. Trautz Technical Executive US-Taiwan International CCS Conference April 17 21, 2017

2 Acknowledgments This material is based upon work supported by the Department of Energy National Energy Technology Laboratory under Award Number DE-FE and was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. 2

3 Presentation Outline Benefits Principles of operation Distributed acoustic sensing (DAS) US Department of Energy Regional Carbon Sequestration Partnership DAS demonstration at the SECARB Citronelle Alabama Project Time-lapse seismic results (June 2014 and Dec 2015) Shear-wave seismic source survey (Dec 2015) 3

4 Fiber Optic Based, High Density Sensor Arrays Benefits: Fiber optic cables can operate in harsh downhole environments, long life span (50 yrs), high data transfer rates, high spatial resolution, easily adaptive to changing technologies, and have many applications Applications include: Distributed temperature sensing Strain measurements Heat-pulse monitoring Leak Detection CO 2 distribution behind casing Flow monitoring and allocation High density seismic arrays Leak detection Compliance monitoring 4

5 Principle of Operation: Distributed Acoustic Sensing (DAS) for CO 2 Plume Imaging Light emitted into a fiber is reflected throughout the fiber s length by Rayleigh scattering DAS system measures the modulation of the backscattered light An acoustic field around the fiber exerts tiny pressure/strain changes on the fiber, resulting in changes to the backscattered light The DAS measures these changes by generating a repeated light pulse every 100 μs and continuously processing the returned optical signal, thus interrogating each meter of fiber up to 10 km in length at a 10 khz sample rate Unlike other methods, the system records the full acoustic signal, including amplitude and phase A 10 km single mode fiber becomes a high density acoustic array with 10,000 linear sensors with 1 meter spatial resolution 5

6 DOE Regional Carbon Sequestration Partnership Program US Department of Energy funds Seven Regional Carbon Sequestration Partnerships Phase III Development of commercial-scale geologic storage projects ( ) EPRI and its members provide required industry cost share EPRI has a significant project management and technical role in SECARB SECARB Citronelle AL Storage Site (DOE Carbon Sequestration Atlas of the US and Canada, 2008) 6

7 DAS Application at the SECARB Anthropogenic Test Site, Citronelle Alabama Objective: Demonstrate safe, reliable and permanent CO 2 storage World s first integrated CO 2 capture, transportation and storage project on a coal-fired power station using advanced amines Southern Co. and MHI captured over 240,900 metric tons of CO 2 starting in June 2011 (500 metric tons/day) Alabama Birmingham Montgomery EPRI project team transported, injected and stored over 114,104 metric tons from August 2012 September 2014 Post-injection site care monitoring program will conclude in 2017 followed by well plugging & abandonment and project closeout by 2019 Mobile Citronelle Oil Field Plant Barry, Bucks AL 7

8 Introduction: Time-Lapse Seismic Surveys When CO 2 displaces water in the formation, it changes the acoustic impedance of the rock Acoustic wave velocity decreases and its direct travel time increases Results from repeat surveys performed during or after CO 2 injection can be compared to a preinjection baseline survey to image the extent of the CO 2 plume (referred to as time-lapse differencing or imaging ) Vertical Seismic Profile (VSP) Survey Source/Receiver Configuration 8

9 SECARB Offers a Unique Opportunity to Compare Seismic Sensors to Detect CO 2 Plume Migration Three sensor arrays were used Temporary conventional hydrophone arrays (2 to 80 levels) Regulatory compliance Semi-permanent geophone string in D9-8#2 (18 levels) Research tool, lower resolution Fiber-optic distributed acoustic sensor (DAS) array (0-2,987 m) Research tool, high resolution Semi-permanent array (top left), DAS cable encased in yellow flat pack (top right) and cross-section showing small 9.5 mm cable containing fibers (bottom) 9

10 Semi-Permanent Geophone and DAS Deployment at Monitoring Well D9-8#2 (MBM) Deployment of the Modular Borehole Monitoring (MBM) Conventional geophone array (left) and yellow flat pack containing the fiber optic based DAS array (right) 10

11 Citronelle Offers a Unique Opportunity to Compare Survey Configurations to Detect CO 2 Plume Migration Three survey configurations Cross-well from injector to observation well Pre- and post-injection High resolution time-lapse Offset Vertical Seismic Profile (VSP) Pre- and post-injection Lower resolution time-lapse with azimuthal coverage Walk-away VSP Snapshots at intermediate times D9-7#2 D9-8#2 VSP source offset locations (stars), receiver locations (D9-7#2 injector and D9-8#2 observation), and walk-away lines (blue and red lines) 11

12 June 2012 VSP DAS Results T. Daley et al., Field testing of fiber optic acoustic sensing (DAS) for subsurface seismic monitoring, The Leading Edge, June 2013 SP 2054 located ~100 ft offset from the D-9-8 sensor borehole. Observed two tube waves. SP 2021 located ~700 ft offset from the D-9-8 sensor borehole. Estimated wave speeds for two events (red and blue lines) are labeled in km/s. Seismic energy was recorded by DAS but the signal-to-noise ratio (SNR) was not sufficient to observe P-waves below approximately 1,600 m (i.e., 2.7 km/s event) 12

13 Comparison of Geophone to DAS Response Resulting from Large Source Effort 2013 implemented a large source effort (64 sweeps per shot point) Processed the results using adaptive stacking and spectral rebalancing to improve SNR DAS native measurement is strain rate Converted strain rate to particle velocity (Daley, et al 2015) Daley, T.M., et al. Field Testing of Modular Borehole Monitoring with Simultaneous Distributed Acoustic Sensing and Geophone Vertical Seismic Profiles at Citronelle, AL, Geophy. Prosp. (2015) Wave form acquired using stacked VSP-DAS provides good match with results from conventional geophones! 13

14 Tucsaloosa June 2014 DAS-VSP Survey Results Migrated image - Observed strong reflectors - Good tie to formation logs (e.g., Selma Chalk) Image has sufficient quality to conduct time-lapse analysis using results from the second (final) survey Wilcox Midway Selma Chalk Eutaw Fm. Upper Marine Sh Mass Sand Washita Fredericksberg Interval Paluxy Fairy Lk 14

15 DAS Migrated VSP Images from 2014 (left), 2015 (center) and Time Lapse Difference (right) 15

16 Cross-Well Seismic Survey Configuration ~840 ft D9-7#2 (Injector) D9-8#2 (Observ.) Illustration by: Schlumberger Carbon Services 16

17 Conventional and DAS Crosswell Seismic Baseline and Repeat Surveys Pre-injection baseline survey acquired in 2012 Repeat survey was acquired in 2014 Source well D9-7#2 Receiver well D9-8#2 D9-7#2 D9-8#2 Only one DAS crosswell survey has been performed (2014) Crosswell survey between wells D9-7#2 and D9-8#2 17

18 June 2014 Crosswell DAS Survey Results Conventional DAS Random Noise Coherent Noise Coherent Noise No significant negative velocity anomalies Injection Zone Confining Zone Decrease in velocity (negative anomaly) DAS Data at 9,340 ft Only See Random Noise, Except Some Coherent Noise Not related to sweep DAS cross-well survey (left) showed random noise. DAS is sensitive to the acoustic wave s angle of incidence to the fiber (broadside detection is limited) 18

19 Summary Accomplishments DAS surveys Increased source effort and improved processing methods result in better SNR Wave form acquired using stacked VSP-DAS provides good match with results from conventional geophones DAS cross-well survey exhibited random noise and appears to be limited to high angle of incidence acoustic waves DAS provided a high resolution image of subsurface stratigraphy that matches conventional logs VSP time-lapse surveys show promise for detecting the CO 2 plume T-Rex shear and p-wave vibroseis source (UT-Austin) 19

20 Together Shaping the Future of Electricity 20