25th International Meeting on Organic Geochemistry IMOG 2011

P-303
Evaluation of petroleum systems in the area Carúpano Basin,
offshore Venezuela, through basin modeling 3D
Adriana Pérez, Irenio Berrios
PDVSA-Intevep, S.A., Los Teques, Venezuela (Bolivarian Republic of) (corresponding
author:perezacy@pdvsa.com)
Carúpano Basin is an oval depression covering some
30000 km 2 with a southwest-northeast orientation. It
has around 300 km long and extends from the
Margarita Platform to the Tobago Island. The
presence of hydrocarbons in this area had been
confirmed by the production data of the wells, which
have reported condensate and gaseous
hydrocarbons. The geochemical features of these
hydrocarbons, based in the molecular and isotopic
composition of some samples of gases, suggest the
presence of at least two petroleum systems,
thermogenic and biogenic systems. The aim of this
study was to identify and evaluate the thermogenics
petroleum systems in the area by 3D basin modeling,
in order to contribute to the reduction of uncertainty in
exploratory risk in the basin.
The methodology of this study was based on 1) the
construction of the 3D block 2) gridding, 3) allocation
of the properties of the elements of the petroleum
system and 4) backward and forward modeling. This
methodology permitted to get a 3D block with the
main characteristic of the Carúpano Basin.
Additionally, in this study was done a semiquantitative
evaluation of hydrocarbons thermogenic
generated in the Carúpano Basin, in order to get the
Generation – Acummulation Efficiency (GAE) of the
petroleum systems identified in the basin.
The results of simulations made suggest that of "all
potential source rocks" evaluated in the area, the
Eocene and Oligocene corresponding to principal
sequences that have generated, expelled and have
succeeded in generating accumulations in the
hydrocarbons in the area. Early Miocene sequence
has a level of maturity suitable for the generation but
it has not expelled hydrocarbons to generate
significant amounts of commercial accumulations.
Probably to the moment it began the expulsion, the
traps had not yet developed. At the time of early
Miocene just began the expulsion of hydrocarbons,
the main reservoir (Late Miocene) started its
sedimentation. This reflects the lack of
synchronization between the event generation,
migration and accumulation of hydrocarbons to come
from the lower Miocene sequence, so these
hydrocarbons could not be accumulated. However,
hydrocarbons come from the Eocene and Oligocene
sequences could be accumulated in the sandy facies
of the upper Miocene and lower Pliocene.
Additionally, the Eocene was able to achieve oil
accumulation in the upper sand interval of the same
sequence, in traps associated with anticlines. The
values of the GAE obtained for petroleum systems
described (Eoceno – Eoceno (?), GAE: 0,015 % and
Oligoceno –Mioceno Tardío (?), GAE: 4,12 x 10 -4 %)
are considerably lower and they can be classified as
inefficient.
An important aspect to be considered in the models of
generation, migration and entrapment of
hydrocarbons in this basin is associated with the
distribution of sedimentary facies and especially the
quality of reservoir sands, because information
available from the sedimentary view to define the
extent and thickness of these sequences is limited,
due to the large extension that exists between the
boreholes and the low number of cores and electric
logs. This aspect has affected the value of GAE and
limited the reach and resolution of the models
generated in this study, coupled with the lack of
geochemical data related to the characterization of
the fluids found in the area.
However, the results presented here suggest that this
area has a high potential for hydrocarbon exploration
in the area, not only in the intervals already drilled but
in deeper intervals like Eocene, which should be
studied more carefully, so as to assess in detail the
potential of them, which could increase opportunities
for exploration in the area.
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