Evaluation of Petroleum Systems in the Carúpano Basin, Offshore Venezuela, through 3-D Basin Modeling
The Tertiary Carúpano Basin is located offshore of
northeastern Venezuela. The presence of hydrocarbons in this area had been
confirmed by production of condensates and gas. The molecular and isotopic
composition of gases from some wells, suggest the presence of at least two
petroleum systems, thermogenic and biogenic. The aim of this study was to
identify and evaluate the thermogenic petroleum systems in the area by using 3D
basin modeling; in order to help reduce uncertainty in exploration.
The methodology was based on 1) 3D geometric model
building 2) gridding, 3) assignment of the properties of the elements of the
petroleum system 4) backward
and forward modeling and 5) semi-quantitative
evaluation of hydrocarbons generated in the Carúpano Basin. This
methodology permitted to get a 3D block with the main characteristics of the Carúpano Basin. Semi-quantitative evaluation of thermogenic hydrocarbons
generated in the Basin allowed to get values of generation-accumulation
efficiency (GAE) of the petroleum systems identified in the basin. The results
of simulations suggest that from "all the potential source rocks"
evaluated in the area, the Eocene and Oligocene succession were the most
suitable for generation and expulsion of hydrocarbons. Early Miocene deposits
reached the maturity level for generating but they have not expelled enough
hydrocarbons for commercial accumulations or probably the traps had not
developed yet.
During early Miocene, when expulsion of hydrocarbons began, the main reservoir (late Miocene rocks) started its sedimentation. This reflects the lack of synchronization between the events of generation, migration and accumulation of hydrocarbons from lower Miocene rocks. However, hydrocarbons from Eocene and Oligocene source rocks could be trapped in the sandy facies of upper Miocene and lower Pliocene deposits. Additionally, the Eocene succession retained oil in the upper sands, in traps associated with anticlines. The values of GAEs obtained for the petroleum systems described (Eocene-Eocene (?), GAE: 0,015 % and Oligocene-late Miocene (?), GAE: 4,12 x 10-4 %) are considerably lower and they can be classified as inefficient. However, the results obtained suggest that this area has a high potential for hydrocarbon exploration, not only in the intervals already drilled but in intervals as deep as Eocene, which should be studied in more detail in order increase opportunities for exploration in the area.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California