Gas Detection using Multibeam Mapping Sonar · Gas Detection using Multibeam Mapping Sonar...

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Gas Detection using Multibeam Mapping Sonar

Gas Detection using Multibeam Gas Detection using Multibeam Mapping Sonar

Dr. Jens Schneider v. Deimling

04.11.2010

HYDRO 2010 04.11.2010, Warnemünde


Background and Motivation

• Natural Gas Seepage

• Multibeam WCI ---> New Field of Research


• CCS Measuring, Monitoring, Verification

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Research Cruise Alk259: North Sea 2005



TS= 10*log10(Iref/Iinc)

Echo sounder Backscattering of a bubble

Acoustic impedance contrastWater (surface) ρ1 * c1~1024 * 1450 = 1484800 Gas (surface) ρ1 * c1~0.7 * 330 = 231

Iref ~ geometry of scatterer~ impedance contrast

Resonanceeffects bubbles


Computed using the Andersson scatter model

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Singlebeam

EK60 (38kHz)

---100 m ---



• large coverage 150°

• narrow steered beams 1°

Multibeam

Seafloor mapping

Water column scan limitations so far:

• signal processing

• data storage

BDA


Promote misinterpretation of water column signals as seafloor reflections

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Standard Processing Flare Processingsingle line

Flare Processingmulti line

Research Cruise Alk259: North Sea 2005


Schneider von Deimling, J., Brockhoff, J., and Greinert, J., 2007, Flare imaging with multibeam sonar systems: Data processing for seep bubble detection. Geochem., Geophys., Geosyst. (G3, g‐cubed.org), v. 8, p. 1‐7.


Research Cruise Pos392: Baltic Sea 2009 L3 ELAC SB 3050 (50kHz)


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Research M82: North Sea 2010 Kongsberg EM 710 (70-100kHz)

Low flux

70

m


Schneider Von Deimling J, Rehder G, McGinnis D, Greinert J, Linke P. Multidisciplinary approach to quantify methane gas seepage at Tommeliten (North Sea). subm. Cont. Shelf Res. 2010.

DT: ~20 ml/min.


TransducerLauncher

GasQuant – Insitu Monitoring of Gas L3 ELAC SB 100 (180kHz)

• Frequency: 180 kHz, 0.15 ms pulse

ADCP

Compass


• 21 beams• 512 samples • range 70 m (~10 cm resolution)

Electronic / PC

512 x 21 cellsMax. water depth 1000m

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Noise

Bubbles or fish?


Challenge

• Data processing

• Visualization

• Bubble Pattern


Processed data

56.2

Predicted bubble displacement

Dis

tanc

e [m

]

50.5

54.3


48.6 #50

Schneider von Deimling J, Greinert J, Chapman NR, Rabbel W, Linke P. Acoustic imaging of natural gas seepage in the North Sea: Sensing bubbles controlled by variable currents. Limnol. Oceanogr. Methods. 2010;8:155-171.

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Bubble detection algorithm

measuredLAG

dy

predicted

LAG

dy

d

dt

Estimator Bubble event

50

100

150

200

250

300 bbl

HYDRO 2010 04.11.2010, WarnemündeHYDRO 2010 04.11.2010, Warnemünde

LAGdt

Bubble size vup, vh

ADCP Modelling

x (pixel)100 200 300 400 500 600

300

350

400

Water current

Bubble Dissolution


Subbottom Mapping of Shallow Gas

Free gasmud

Research Cruise MSM16: Baltic Sea 2010

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Conclusion

Modern Multibeam Mapping Sonar

• ideally suited for gas bubble / leak survey-high sensitivity (20ml/minute) -good range, large coverage, precise localization


• WCI offers new potentials• New techniques needed for processing


Acknolwledgements c o edge e ts

• IOW and IFM-GEOMAR

• L3 Elac-Nautik GmbH

• Crew members of various R/V‘s


Gas Detection using Multibeam Mapping Sonar · Gas Detection using Multibeam Mapping Sonar...

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