Anna Stork (University of Bristol) - Microseismic Monitoring at the Aquistore CCS Site - UKCCSRC Cranfield Biannual 21-22 April 2015
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The document discusses microseismic monitoring at the Aquistore CCS site, detailing the significance of tracking small seismic events and their implications for CO2 storage security. It outlines how changes in reservoir pressure and geomechanical deformation can affect fluid flow properties, potentially leading to risks like leakage through fractured caprocks. Various monitoring methods, such as passive seismic monitoring, are highlighted for their role in assessing geomechanical deformation and ensuring safety in CO2 storage operations.
![Regional
event
12
21 April 2015
UKCCSRC Biannual Meeting, Cranfield
21 April 2015
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Fig. 11. Summary figure of the seismicmodeling.Intersectionswith other lines are indicatedby an arrow with the
appropriateline letter circled.Symbolsother than for velocitiesare the sameasfor Figure 10.
zoic times.The strikingsimilaritiesof the velocity-depthpro-
files from the Wyoming and Superior cratons is consistent
with the proposalthat the two cratonsonceformeda continu-
ousArchcancontinentalmassthat wasdisruptedby theopen-
ing and closing of an interveningoceanic basin [Stauffer,
1984]; the remnantsof the closingeventbeingrepresentedby
theTrans-Hudsonorogen[Greenetal., 1985a,b].
SouthwardExtensionof the SuperiorCraton Margin
An important exception to the uniformity emphasized
above is the high-velocity(6.4 km/s) lid within the southern
extensionof the Superiorcratonmargin(Thompsonbelt).The
northerntip of the lid occursnear a southwardchangein the
character of the magnetic and gravity fields [Green et al.,
1985a,1986b]and is probablyrelatedto granulitefaciesbase-
ment rocks in this region [Peterman and Hedge, 1964; Peter-
beneath the lid. According to Jonesand Savage[1986] the
anomalous conducting structure is subvertical, and recent
two-dimensionalmodelingby A. G. Jones(personalcommuni-
cation, 1986) indicatesthat the structure may be lessthan 5
km wide with its top surfacesome400 m below the baseof the
Phanerozoicsediments,placingit immediatelybelow the high-
velocitylid. A multichannelseismicreflectionsurvey[Greenet
al., 1985a-Ihas revealeda zone of prominent reflectionsdip-
ping to the west at 300-40ø(R in Figure 10) in the vicinity of
the Thompson fault (TF in Figure 10). The reflectorslie well
below the high-velocitylid, but they parallel the minor veloci-
ty discontinuitybetweenthe Superior craton margin and the
Trans-Hudson orogen, which was delineated independently
from the seismicrefractiondata (notethe verticalexaggeration
of Figure 10).
Green et al. ['1985a, b, 1986b] have interpreted the various
Regional seismic refraction study Regional velocity model
to find tsp times as
function of distance
Morel-à-l’Huissier et al., JGR, 1987](https://image.slidesharecdn.com/annastorkuniversityofbristolmicroseismicmonitoringattheaquistoreccssitecranfieldbiannual21-22april-150428081757-conversion-gate02/85/Anna-Stork-University-of-Bristol-Microseismic-Monitoring-at-the-Aquistore-CCS-Site-UKCCSRC-Cranfield-Biannual-21-22-April-2015-12-320.jpg)
Anna Stork (University of Bristol) - Microseismic Monitoring at the Aquistore CCS Site - UKCCSRC Cranfield Biannual 21-22 April 2015
- 1. Microseismic Monitoring at the Aquistore CCS Site Anna L. Stork1, J.-‐Michael Kendall1, Don White2 and James P. Verdon1 21 April 2015 UKCCSRC Biannual MeeGng, Cranfield 1. School of Earth Sciences, University of Bristol 2. Geological Survey Canada
- 2. 1. What is a microseismic event? • Small earthquake, usually magnitude < 0. 2. What is passive seismic/ microseismic monitoring? • Groups or array of geophones/ seismometers deployed to record any seismic events. UKCCSRC Biannual Meeting, Cranfield 21 April 2015 2 21 April 2015 changes in the applied stress both in and around the reservoir. Small amounts of deformation are common in many settings, and will not pose a risk to storage security. However, if deformation becomes more substantial, it can affect storage operations in a number of ways, illustrated schematically in Fig. 1. The prin- cipal risks posed by geomechanical deformation to secure storage are summarized below. Reservoir Inflation and Alteration of Flow Properties. Pore pressure increase and inflation can influence the flow properties of a storage reservoir. Laboratory experiments show that perme- ability is sensitive to pressure (15). Furthermore, pore pressure increases may open existing fracture networks in the reservoir, or create new ones, along which CO2 can flow more rapidly. Per- meability increases within the reservoir will not pose a direct leakage risk. Nevertheless, if permeability is increased during injection, this will reduce the accuracy of fluid flow simulations used to predict the resulting CO2 distribution. The result may be that CO2 reaches spill-points or breaks through at other wells faster than anticipated, reducing the amount of CO2 that can be stored. For example, Bissell et al. (16) have shown that injectivity at In Salah is pressure dependent, implying that CO2 flow is controlled at least in part by the opening and closing of fractures in the reservoir. Fracturing of Sealing Caprocks. Deformation in a reservoir is generally transferred into the surrounding rocks. This can lead to the creation or reactivation of fracture networks around and above a reservoir. Fractures running through an otherwise impermeable caprock could compromise the storage integrity, providing permeable pathways for CO2 to escape from the reservoir. This is probably the greatest risk to storage security posed by geomechanical deformation. Leakage of gas through fractured caprock has been observed above hydrocarbon res- ervoirs (17, 18) and at natural gas storage sites (19). Triggering of Seismicity. Beginning with the earthquakes triggered by waste fluid injection at the Rocky Mountain Arsenal (20), it has been recognized that subsurface fluid injection is capable of triggering felt (of sufficient magnitude to be felt by nearby populations, so typically ML > 2) seismic events on preexisting tectonic faults (21). Recently, examples of tectonic activity trig- gered by disposal of waste water from hydraulic fracturing have been noted. Of course, it should be kept in mind that, of thou- sands of fluid injection wells, only a handful have experienced such seismic events (22). Even if felt seismicity is induced during CO2 injection, it is unlikely that events would be of sufficient integrity posed by mechanical effects in the wellbore is an issue that must be considered at future storage sites. Monitoring Geomechanical Deformation Fig. 1 also illustrates the variety of methods that can be used to monitor geomechanical deformation in the field. Although the importance of geomechanical deformation in oil production is becoming increasingly appreciated, monitoring it in the field remains something of a niche activity. Nevertheless, a number of SATELLITE GEODESY SEISMIC MONITORING MICROSEISMIC MONITORING BOREHOLE TILTMETERS BEDDING PARALLEL SLIP SURFACE UPLIFT WELLBORE FAILURE FAULT REACTIVATION SEAL FRACTURING INFLATION OF RESERVOIR Fig. 1. Schematic illustration showing how geomechanical deformation can influence CO2 storage sites (red text), and potential monitoring options (blue text). Adapted from Herwanger and Horne (34). 2 of 10 | www.pnas.org/cgi/doi/10.1073/pnas.1302156110 Verdon et al. Verdon et al., PNAS, 2013
- 3. Why deploy passive seismic monitoring at CCS sites? • Track fluid movement • Map faults/fractures • Real-‐Gme analysis • Verify geomechanical models • Do models predict seismicity? • Observed seismicity feedbacks new informaGon into models UKCCSRC Biannual Meeting, Cranfield 21 April 2015 3 21 April 2015
- 4. • Weyburn, Saskatchewan, Canada • CCS-‐EOR • ~100 events • InSalah, Algeria • Gas field • ~9000 events in 2 years • Seismicity in lower caprock • Neither thought indicaGve of CO2 leakage • At Aquistore, what will the response be? • InjecGon into deep saline aquifer, above Precambrian basement in non-‐ producing area 4 21 April 2015 jection-induced seismicity theory suggests that seismicity should be induced at the injection points, where elevated pore pressures lead to reduced effective normal stresses. The events above the reservoir may also be of concern if they indicate fracturing and hydraulic communication into the overburden. Conversely, the events that occurred after shut-in of the in- jection well were found to cluster around the injection point (red through horizontal wells. They assessed the likelihood of mi- croseismicity by considering the development of both shear and normal stresses via a fracture potential term (49), finding that, although normal stresses are reduced at the injection point, so are the shear stresses. This means that the potential for seismicity is not increased by injection. Indeed, the shear stress reduction slightly exceeded the effect of normal stress reduction, causing Northing(m) 500 250 0 -250 5002500-250 Easting (m) 5002500-250 Easting (m) Depth(m) 500 1200 1300 1400 1500 A B Fig. 5. Locations of microseismic events recorded at Weyburn between 2003 and 2010, in map view (A) and projected onto an E–W cross-section (B). In A, the locations of the injection wells (stars), monitoring well (gray triangle), and horizontal producing wells (black lines) are marked. In B, the geophones (gray triangles), injection wells (purple lines), and production wells (black lines) are marked. The reservoir interval can be identified from the depth of the lateral wells. Events are colored by occurrence time: before CO2 injection (yellow), during the initial injection stages (dark blue), during a period of elevated injection, Summer 2004 (green), during the second phase of monitoring, 2005–2006 (light blue), and after injection well shut-in September 2010 (red). The location of the microseismic monitoring area with respect to the oilfield is shown by the dashed square in Fig. 3A. Verdon et al. PNAS Early Edition | 5 of 10 UKCCSRC Biannual Meeting, Cranfield 21 April 2015 Previous CCS passive seismic analysis Weyburn Verdon et al., PNAS, 2013 In Salah Stork et al., IJGGC, 2015
- 5. Monitoring Program • Regional 3D seismic survey • Permanent seismic array • Electrical / electromagneGc • Gravity • Passive seismic • InSAR • GPS • Tiltmeters • Groundwater & soil monitoring 5 • Cross-‐well seismic & VSP • Cross-‐well & surface-‐to-‐downhole electrical monitoring • Real-‐Gme P & T • Passive seismic • Fluid sampling • Tim-‐lapse logging • Distributed acousGc / temperature sensors (DAS/DTS) • Gravity Surface monitoring Downhole monitoring Image: Geomatics Canada
- 6. • Covers 2.5km x 2.5km • Geophones (>10Hz) • 51 verGcal component • 20m deep • Since July 2012 • 25 3-‐component • 6m deep • Since Nov 2014 • Surface • 3 broadband (0.1 – 50Hz) seismometers • Since Nov 2013 UKCCSRC Biannual Meeting, Cranfield 21 April 2015 6 21 April 2015Microseismic Monitoring
- 7. 7 21 April 2015 Ben Rostron et al. / Energy Procedia 63 (2014) 2977 – 2984 Figure 4. Schematic of the 01/5-6-2-8W2 injection well. Approximate locations of major geological units are indicated (left) drawn to vertical depth scale. One week after completion of the injection well, the drill rig was moved 150m northeast (Figure 1) and over the period October 1st to November 9th, 2012 the observation well (41/5-6-2-8W2) was drilled 3400m deep through the entire Phanerozoic section (schematic on Figure 5). A similar suite of geophysical well logs was collected from the observation well as was the injection well. Rostron et al., Energy Procedia, 2014 Injection well Subsurface model UKCCSRC Biannual Meeting, Cranfield 21 April 2015
- 8. 8 Passive Seismic Baseline Seismic event detecGon • STA/LTA coincidence detecGon • Local • Regional • Teleseismic (long distance) • Noise Local detection 21 April 2015
- 9. 9 21 April 2015 Local seismic event? UKCCSRC Biannual Meeting, Cranfield 21 April 2015 P S? tsp = 2s
- 10. 10 Geophone recording -‐ Local seismic event? -‐ Distance 5km W 21 April 2015 x 2.3s UKCCSRC Biannual Meeting, Cranfield 21 April 2015
- 11. 11 21 April 2015 UKCCSRC Biannual Meeting, Cranfield 21 April 2015 Local seismic event? Approx 17:30 – 18:30 most days most likely mining related
- 12. Regional event 12 21 April 2015 UKCCSRC Biannual Meeting, Cranfield 21 April 2015 MOREL-.,•-L'HuISSIERET AL.' REFRACTIONSURVEYIN CENTRALCANADA 6417 N LINE A s •) 0 100 200 km -r :.......•1...L_.!....I.....,.._.•• '•20{:ii:'!.".... .................... N LINED t• k, S0 100 O0 rn 0 i i I I iT i I i I I 20- 40 6O NW LINE F SE O 1OO 200 krn N LINE C •) s 0 100 T200 krn 0 L.. •' ,J.L.._• •_ ....-L%! • t i'• I t I , ß..•..,•..•-.•...'%.'P....ff....'...*if....•,..7..•7..-'........:-.............?.....,.........-...-.-.-.'.-...;.:,-.'.'.'.:: •............. ••:•::•::::::::•:::.:.:.:.:.:••.•.•.:.:.:.•.:.••:.:.•.:.:.•.7..:.:•:•:.::::••:•:::::::::::•••::•:::::::::::::::::•::•••::•:.:.:.•.:.:.:.•.:.•.:.•.:.:.:.•.:.:.•.:.•••• NLINEE ,o• s0 100km 20 I I I I0 t I I iT I I i i 20' 40 60 sw LINE G NE 0 100 200 km :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::..•:::::::::::•:::7:::::.:::::.":::::::..:.:.:.:.:.:.:: .:::.:.:•:.::.:.:.:.:.:...=.:.:.:.:.:•.:.:.:.:.:...•.:.:.:•:.:.:.:•:.:•:.:.:•:.:.:.:.:.:.:.:;.:.:.:.:.:.:.!.:..:.. '.:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::.x::::::::::::::::::.:::.:.:.:.:-:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:::::::::::::::.': r",40 40 601 60 WE-WLINE1o,o• • Fw,•0 ..... T•,F,. , T ,.4?Okra,gQi , , • o •.::•::...•:*:.:::•::.:•::•:•:•:;•`:*:•:`.•:*:.:•:•::•`:*:•:::.:•..•..•..•..•................r..................71........................................................................................................I...................................................i• t.....:.:.:.:.:.............:::.........:.......::::::::::::::::::::::::::::::......:.:.:.:.:...........ii•......:':':...........:':':.............:':.........:':::......:::::::::::::::::::::::::::::::::..............:.............t.......:.............:..........:.::::::::::::....... E 20 r-,,40 60 ]2.1-5.8km/s I 5.5km/s •tlJ_[•6.4-6.8km/, • 7.0-7.2km/s IITFi ,8.0km/s Fig. 11. Summary figure of the seismicmodeling.Intersectionswith other lines are indicatedby an arrow with the appropriateline letter circled.Symbolsother than for velocitiesare the sameasfor Figure 10. zoic times.The strikingsimilaritiesof the velocity-depthpro- files from the Wyoming and Superior cratons is consistent with the proposalthat the two cratonsonceformeda continu- ousArchcancontinentalmassthat wasdisruptedby theopen- ing and closing of an interveningoceanic basin [Stauffer, 1984]; the remnantsof the closingeventbeingrepresentedby theTrans-Hudsonorogen[Greenetal., 1985a,b]. SouthwardExtensionof the SuperiorCraton Margin An important exception to the uniformity emphasized above is the high-velocity(6.4 km/s) lid within the southern extensionof the Superiorcratonmargin(Thompsonbelt).The northerntip of the lid occursnear a southwardchangein the character of the magnetic and gravity fields [Green et al., 1985a,1986b]and is probablyrelatedto granulitefaciesbase- ment rocks in this region [Peterman and Hedge, 1964; Peter- beneath the lid. According to Jonesand Savage[1986] the anomalous conducting structure is subvertical, and recent two-dimensionalmodelingby A. G. Jones(personalcommuni- cation, 1986) indicatesthat the structure may be lessthan 5 km wide with its top surfacesome400 m below the baseof the Phanerozoicsediments,placingit immediatelybelow the high- velocitylid. A multichannelseismicreflectionsurvey[Greenet al., 1985a-Ihas revealeda zone of prominent reflectionsdip- ping to the west at 300-40ø(R in Figure 10) in the vicinity of the Thompson fault (TF in Figure 10). The reflectorslie well below the high-velocitylid, but they parallel the minor veloci- ty discontinuitybetweenthe Superior craton margin and the Trans-Hudson orogen, which was delineated independently from the seismicrefractiondata (notethe verticalexaggeration of Figure 10). Green et al. ['1985a, b, 1986b] have interpreted the various Regional seismic refraction study Regional velocity model to find tsp times as function of distance Morel-à-l’Huissier et al., JGR, 1987
- 13. 13 21 April 2015 13 April 20, 2015Array analysis Use geophones / seismometers as a group. Example: Broadband seismometer detecGon of teleseismic event, M=6.5 in Barbados Azimuth 1/v=0.20 Time Power1/velocity Particlemotion angle
- 14. 14 21 April 2015 PerforaGon shots • 13 perforaGon shots • Only 3 shots with 10 or more recordings • Sept 2012 • 3173m – 3366m • Mw= 0.6 UKCCSRC Biannual Meeting, Cranfield 21 April 2015
- 15. • Ambient Noise Tomography / Seismic Interferometry • Cross-‐correlaGon of noise • No microseismic events required! • 2 years background data • Up to 50 instruments 15 21 April 2015 Work in progress… Body wave and higher modes Although the theory (equation 1) suggests that the entire Green’s function can be derived from the noise crosscorrelation for a diffuse noise field, in reality, the noise sources are distributed gen- erally near the surface and hence body wave phases are not easily observed. However, extracting body waves from ambient noise 200-m distance bin (Figure 13). Because body waves/higher modes are more sensitive to deeper structure compared with fundamental Rayleigh waves, they tend to stack more coherently due to a smaller velocity variation. Clear body waves/higher models can be observed for low and high frequencies. Between 2 and 4 Hz, a clear P-wave signal emerges with an ~2-km/s apparent velocity. –15 –10 –5 0 5 10 15 0.0 0.5 33.84˚33.82˚33.80˚33.78˚33.76˚ 0.0 0.5 0.0 0.5 0.0 0.5 33.84˚33.82˚33.80˚33.78˚33.76˚ 0.0 0.5 0.0 0.5 33.84˚33.82˚33.80˚33.78˚33.76˚ Latitude (°) VS perturbation (%) A´ A B´ B C´ C Depth(km) Figure 11. The three cross sections (Figure 9a) of the inverted 3D shear velocity model. Here, the average 1D model shown in Figure 10a is used as the reference and only the relative perturbation at each depth is plotted. The contours are separated by 5% VS velocity perturbation. 0 0.2 0.4 0.6 0.8 0.3 0.5 0.7 0.9 1.1 Avg. VS (km/s) Depth(km) 2 Hz 1 Hz 0.67 Hz 0 0.2 0.4 0.6 0.8 Normalized sensitivity Depth(km) 0 0.120.06 0.14 a) b) Figure 10. (a) Average 1D shear velocity model. (b) Depth sensitivity kernels for 0.67-, 1-, and 2- Hz Rayleigh waves calculated based on the 1D model shown in (a). Lin et al., Geophysics, 2013 UKCCSRC Biannual Meeting, Cranfield 21 April 2015 * • ConsideraGons: • Suitable available frequencies • DirecGonality in noise • Especially nearby power staGon • Roads Lin et al., Geophysics, 2013
- 16. • RouGne event detecGon, locaGon & magnitudes • Beamforming & surface array methods • Event detecGon • Event locaGon • Noise idenGficaGon &/ removal • Baseline shows seismically quiet area • What will we observe? … • Visit Geological Survey Canada – UKCCSRC funded 16 21 April 2015 To do… & Conclusions UKCCSRC Biannual Meeting, Cranfield 21 April 2015
- 17. BRISTOL UNIVERSITY MICROSEISMICITY PROJECTS BUMPS UKCCSRC Biannual Meeting, Cranfield 21 April 2015 We thank PTRC for providing the data and permission to present this work.