Page 638 - Economia Azul - versão: inglês

b
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A 3-D controlled source electromagnetic in the area also indicate fluid flow related Figure Z5
(CSEM) survey of the areas where the pock- chimneys not yet connected to the surface
marks are concentrated allowed the distinc- (Figure Z4). The inversion of the CSEM data
tion between a chimney that possibly has also reveals that the gas below the BSR mi-
trapped fluid and a chimney that seems to grates along the faults through the GHSZ
have allowed all the gas to leak towards forming bodies rich in gas hydrate with
the seabed (THARIMELA et al, 2019). The gas hydrate saturation of 40-60% (THARI-
method is based on the resistivity difference MELLA et al., 2019). It also shows that the
between the highly resistive free gas and anomalous amplitudes below the BSR in
the sediment bearing salt water and/or hy- the seismic data may represent free gas ac-
drate with lower resistivity. Other locations cumulations (Figure Z5).

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Figure Z4: (A) Backscatter image of the Bottom: high-resolution seismic profile,
seabed highlighting the expression of correlated. The largest resistivity anoma-
-1000
surface faults and the area covered by the lies within the gas hydrate stability zone -1000
controlled source electromagnetic survey are possibly associated with gas hydrate
(3-D CSEM yellow polygon). The yellow saturations. Note that it also revealed gas -2000 ---------- --------------
----
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arrow highlights the occurrence of pock- chimneys not yet connected to the sur- -2000 ---------- ---- ----- -------------- 2.20 ::É
2.20 ::É
2.37 1:
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mark 22 - Figure Z2). (B) Top: CSEM pro- face, as well as the CSEM expression in the --- --------- ----- - - ---- --- 2.37 0 0
2.70 .C
Zone of highest concentration of free gas
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Zone of highest concentration of free gas
2.67
2.70
3.21 '·"'
2.67
file illustrating the anomalies identified subsurface of the pockmark area. -3000 --- --------- ----- - - ---- --- 3.38 -
3.21
3.38
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-3000
3.55
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in the inversion (warm colors). Source: Authors elaboration, 2022 4.00
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-4000
Figure Z4
-2000
-2000
Zone of highest concentration of free gas
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-3000
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Source: Authors elaboration, 2022
Figure Z5: (A) Backscatter image of the of electromagnetic anomalies. (C) Pro-
seabed highlighting the expression of sur- file illustrating the anomalies identified
face faults and the area covered by the in the inversion of the CSEM data (warm
Source: Authors elaboration, 2022 controlled source electromagnetic survey colors). (D) Seismic profile correlated with
(3-D CSEM yellow polygon). (B) 3-D view the profile in (C). The overlap revealed gas
637
State of the Art of Gas Hydrate Occurrences
636 BLUE ECONOMY State of the Art of Gas Hydrate Occurrences 637