25th International Meeting on Organic Geochemistry IMOG 2011

P-064
Biodegradation of Aromatic Hydrocarbons at Basin and
Laboratory Scales
Frank Haeseler, Françoise Behar, Denis Blanchet, Marion Courtiade
IFP New Energy, Rueil Malmaison, France (corresponding author:frank.haeseler@ifpen.fr)
Oil biodegradation at Basin scale has been shown by
Haeseler et al. 2010 to be a compositional process for
which different classes of hydrocarbons are degraded
in parallel. These concepts are implemented in the
BioClass 0D model which describes the compositional
changes and determines the hydrocarbon losses. In
this model the classes are subdivided according to
chemical criteria (saturated and aromatic, light and
heavy) and they are characterised by specific relative
kinetics. The susceptibility to biodegradation (Kbio
factors) has been found very similar for two very
different Basins: Potiguar and Williston.
The aim of the present study is to quantify the
hydrocarbon loss in the aromatic fraction. For that
purpose we used a quantitative GC2D technique
described by Vendeuvre et al. (2005) in which
aromatics are characterized in both number of
aromatic rings and length of site chain. Consequently
it is possible to quantify the loss of HC as a function of
aromatic rings and carbon number of the alkyl chain.
The Figure 1 illustrates the separation and
identification potential of this method for the
phenanthrene / alkyl-phenanthrene region of the 2D-
GC chromatogram. This procedure was applied to a
natural series of reservoir biodegraded oil and to an
oil that has been exposed under aerobic and
anaerobic conditions to specifically adapted
hydrocarbon degrading microflora. So far a
comparison can be done between basin and aerobic
condition.
C 1 -Phe
0,170%
Phe
0,066%
C 1 -Phe
0,375%
(-3,3%)
Phe
0,166%
(-8,6%)
C 3 -Phe
0,189%
C 2 -Phe
0,211%
C 3 -Phe
0,0572%
(-3,0%)
C 2 -Phe
0,603%
(-2,7%)
Figure 1: Zoom in a GCxGC chromatogram of an oil before
biodegradation.
Figure 2a shows that the C1-monoaromatic (e.g.
toluene) behaves in a very similar way under lab and
basin conditions. The sum of the C6-monoaromatic
hydrocarbons present a linear trend in the aerobic lab
scale oil whereas its biodegradation seems to start
and to become very efficient at later times in basins
(Fig. 2b). The C15-monoaromatic hydrocarbon class
shows another behaviour: linear loss for the aerobic
process, no biodegradation in basins (Fig. 2c). C2naphtenodiaromatics
are recalcitrant in lab conditions
and become strongly biodegraded in severely
biodegraded oils at basin scale (Fig. 2d).
Residual mass in one Ton [kg] aerobic
Residual mass in one Ton [kg]
20
18
15
13
10
8
5
3
Aerobic
a
Basin
0,40
0,30
5
4
b
0
0,00
0 10 20 30 40 50 60 70 80 90
2,5
2,0
1,5
1,0
0,5
Biodegradation loss, oil [%]
0,0
0 10 20 30 40 50 60 70 80 90
c
Biodegradation loss, oil [%]
Aerobic
Basin
0,50
0,20
0,10
Residual mass in one Ton [kg] Basin
Residual mass in one Ton [kg]
Residual mass in one Ton [kg]
6
3
2
1
0
0 10 20 30 40 50 60 70 80 90
2,0
1,8
1,5
1,3
1,0
0,8
Biodegradation loss, oil [%]
Aerobic
Basin
0,5
0 10 20 30 40 50 60 70 80 90
Biodegradation loss, oil [%]
Figure 2: Residual mass of C1- (a), C6- (b) and C15-(c)
monoaromatic and C2- (d) napthenoaromatic hydrocarbons.
This work shows that aromatic hydrocarbons with
different number of carbon atoms (7, 12, 19 and 25)
can behave very differently according to their
chemical structure (ring numbers and chain length)
and to the biological process they have been
subjected to.
Insight in their structure with GCxGC contributes to a
far better understanding of the biodegradation and
may contribute in the future to determine the process
(aerobic or anaerobic).
Furthermore, GCxGC analyses also provide similar
data for saturated hydrocarbons and particularly
napthenes. These data of course also contribute to a
better understanding of the hydrocarbon
biodegradation and will be presented during the
conference.
References
Haeseler et al, 2010, Organic Geochemistry, 41, 1156–1170.
Vendoeuvre et al., 2005, Journal of Chromatography. 1090,
116-25.
Aerobic
Basin
d
209