--> Abstract: Hydrocarbon Prospectivity of Intermontane Basins in the Andean Orogen, by Disalvo, Alfredo; Inigo, Juan; Apreda, Diego; and Iribarne, Martin; #90166 (2013)

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Hydrocarbon Prospectivity of Intermontane Basins in the Andean Orogen

Disalvo, Alfredo1; Iñigo, Juan; Apreda, Diego; and Iribarne, Martin
1[email protected]

Through the 8000 kms extension of the Cordillera de los Andes there are several sedimentary basins within the present day orogen. Most of these are defined as intermontane foreland basins, formed among basement-cored uplifts in foreland settings. Tectonic load is the main subsidence driving mechanism in a first evolutionary stage, associated to inversion of Mesozoic rifts. A second stage is given by subsidence related to sediments load and compaction. Examples of this type of basins are the Upper Mag, Middle Mag, Cesar, Santiago, Huallaga, Metan, Uspallata, ñirihuau, etc. In general they involve a multiepisodic sedimentary fill, comprising at least 4 sedimentary super-cycles that include: a granitic or metamorphic basement, Paleozoic marine sediments, lacustrine or marine Mesozoic deposits related to rifting; Upper Cretaceous and Paleogene foreland deposits; and finally Neogene continental and eventually volcanic sediments Strike slip related basins like Lower Mag are rare, as are the extensional "bolsones" of the Altiplano Boliviano-Argentino, or the Loncopue trough in the Cuenca Neuquina.

Except for the prolific basins in the Rio Magdalena, intermontane basins have not been explored for hydrocarbons; this could be related to their limited sizes, their remote location, or to environmental problems. In spite of this, giant accumulations have been found in Pungarayacu and Oglan in Ecuador; smaller sized fields have also been found like those of Pirin in the Peruvian Titicaca basin, and Cuchuma-Lumbrera in Argentina. In some other intermontane basins, abundant oil shows have been found both in outcrop and in the fewer wells drilled; examples of these are Santiago, Huallaga, Ene-Pachitea, Potosiacute; and Tres Cruces among others. In all of them, all the elements of the petroleum system have been proved.

Highest prospectivity would be associated to those basins were Paleozoic sedimentary fill has been preserved, such as Ene for gas and condensate prospection. Also, in those basins that hold a thick Mesozoic marine or lacustrine sequence, like Huallaga in Peru, Santiago in Peru-Ecuador and Tamberiacute;as in Argentina. The ñirihuau basin in Argentina, represents a particular scenario, since it holds Miocene lacustrine sediments in the intermontane fill-stage; this could be an excellent source rock if the oil generation window is reached.

 

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013