Monitoring marine oil seeps from space: the African case. DEFFONTAINES Benoît.1 RIAZANOF Serge 2, NAJOUI Zhour 1,2 , FACON Michael 2
1 Université Paris-Est, GTMC, Marne-la-Vallée, France 2 VisioTerra
Study framework
Data and
PS-InSAR method
References
A
Methodology
Oil slicks in radar images
Oil slicks floating on the sea surface becomes visible
on radar images because it damps the short gravity-
capillary waves that are responsible for the radar
backscattering (Fig.1).
A huge amount of radar data to detect oil slicks
VisioTerra has gathered more than 45 TB of ERS
SAR (Synthetic Aperture Radar) and Envisat ASAR
data across the world, whose 10383 segments for
Africa (Fig.2).
“World Oil Seepages “ database
Our goal is to locate, characterize, quantify and
modelize oil seepages using data acquired since
lunched of Radar satellites the scope to provide new
targets for oil exploration and production.
oil slick clean sea surface
Fig. 2: Studies performed around Africa in which at least 50 dates (red areas) have been collected.
Fig. 3: Numerous oil seeps observed on a ENVISAT ASAR image acquired on 25 February 2012 over Congo and Angola
Fig. 1: Backscatter radar waves on the sea surface.
Pre-processing
Original methods have been developed to numerically
process the images (Fig.4).
Co- occurences
The size, accessibility and gratuity of remote sensing
image archives allow to measure the repeatability of
events in one place. Thus, the seeps escaping from the
same fault appear on radar images on different dates
creating a astroseeps structures (Fig.5).
At least 50 acquisitions have been used in any point
within the 400 km away to the shore to guarantee the
statistical robustness of the discoveries (Fig 6).
Exogenous data
Geological data
Wind fields (Fig.8)
Bathymetric data
Petroleum platforms (Fig. 7)
AIS (Fig.9)
Fig. 4: Example of application of a model-based equalization and inter-swath correction
Fig. 8: Wind fields on 2012-03-15 at 21h42’38’’.
Oil seeps case examples
Application to structural geology
and oil exploration
current
sea surface outbreak
sea floor leak
source
sea surface outbreak e1(t1)
sea floor leak f1
source
current c(t2)
sea surface outbreak e1(t2)
current c(t1)
oil droplet
sea surface outbreak e2(t1)
sea floor leak 1
courant c(t1)
sea surface outbreak e1(t1)
sea floor leak 2
fault
outbreak segment
source
Fig. 5: Example of astroseeps structure observed in the Lower Congo basin (A). Min value of the images show an astroseeps (B).
2005-06-29
2005-05-09
2002-12-26
2002-11-21
2004-06-03
2003-11-25
2003-10-05
2012-02-25
A
B A. Gay, M. Lopez, C. Berndt, M. Sérane, 2007. Geological controls on
focused fluid flow associated with seafloor seeps in the Lower Congo
Basin. Marine Geology 244, p 68-92.
M. Brownfield, R. Charpentier 2006. Geology and total petroleum
systems of the West-Central coastal province (7203), West Africa. USGS
bulletin 2207-B, 52 p.
Z. Anka, R. Ondrak, A. Kowitz, Niels Schodt, 2013. Identification and
numerical modeling of hydrocarbon leakage in the Lower
Congo basin: Implication on the genesis of km-wide seafloor mounded
structures. Tectonophysics 604, p 153-171.
2012-03-26
2012-03-15 2005-02-19
2005-10-12 2005-10-12
2012-03-15
Fig. 10: Different astroseeps (multidates seeps).
Fig. 7: Mean images radar of West Africa.
Fig. 6: Occurrence map of west Africa.
Fig. 9: Automatic Identification System (AIS).
G. Marcano, Z. Anka, R. di Primo, 2013. Major controlling factors on
hydrocarbon generation and leakage in South Atlantic conjugate
margins: A comparative study of Colorado, Orange, Campos and
Lower Congo Basins. Tectonophysics 604, p 172-190
C. R. Jackson, J. R. Apel, 2004. Synthetic aperture radar marine
user’s manual. U.S. department of commerce, National Oceanic and
Atmospheric Administration.
S. Robla, E.G. Sarabia, J.R. Llata, C. Torre-Ferrero, J.P. Oria, 2010.
An Approach for detecting and tracking oil slicks on satellite
images. OCEANS 2010 , vol., no., pp.1,7, 20-23.
Fig. 11: Geological domains in the Lower Congo Basin.
Fig. 12: Weighted density map. Fig. 15: Line drawing of the seismic profile AB (modified after Rouby et al., 2002). The post-rift stratigraphy is characterized by two levels of seismic architectures: (1) an Albian to Eocene sequence containing the source rocks and (2) an Oligocene to Present sequence containing the reservoirs (turbiditic channels) and the sedimentary cover (affected by polygonal faults). Deep thermogenic fluids migrating from the source rocks are preferentially trapped into the silty–sandy channels (Gay and al. 2007).
Fig. 13: Events chart for the Congo Delta Composite Total Petroleum System and the Central Congo Delta and Carbonate Platform and the Central Congo Turbidites Assessment Units. Light blue indicates secondary occurrences of source rocks depending on quality and maturity of the unit. Age ranges of primary source, seal, reservoir, and overburden rocks and the timing of trap formation and generation, migration, and preservation of hydrocarbons are shown in green and yellow. Aptian Loeme Salt (regional evaporite unit) is shown in pink. Age, formation, and lithology modified from McHargue (1990), Schoellkopf and Patterson (2000), and Da Costa and others (2001) (Brownfield and al. 2006).
Fig. 14: Bathymetric map of Congo, extending from the Zaire estuary to the deep-sea fan, acquired during GUINESS (1992–1993) and ZAIANGO (1998–2000) projects (Gay and al. 2007).
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