Loma La Lata giant gas field from a petroleum paleosystem, Neuquen Basin, Argentina
- YPF, S.A., Avenue Roque Saenz Pena, Buenos Aires (Argentina)
The elements of a fully developed petroleum system may undergo later modifications, transforming it to a new system. We define the original system as a Petroleum Paleosystem. In the evolution of the Loma La Lata gas field, diagenetic processes have played a major role in the entrapment since reservoir, lateral and top seals consist of eolian sandstones. The gas origin can be explained as an early oil accumulation trapped between the Late Jurassic to Early Tertiary (petroleum paleosystem) that since Late Tertiary underwent a weak but sufficient thermal degradation to provoke the oil cracking resulting in the co-generation of wet gas+condensate+pyrobitumen-like residue. The elements of the paleosystem are: the Kimmeridgian eolian sandstones of the Sierras Blancas Formation+Catriel Formation as reservoir; the source rock and vertical seat is the rich organic matter marine shales associated with the 139 Ma MFS of the Vaca Muerta Formation; the lateral seal is the eolian facies of the Sierras Blancas Formation that experienced very early diagenesis under the strong influence of the phreatic oscillations in areas of maximum subsidence (Sauzal Bonito); the structural trap is related to the Cenomanian tectonic inversion phase; the expulsion peak was reached in the Late Eocene (40 Ma) and the migration from Vaca Muerta Formation. In the last 5 Ma the paleosystem was transformed by processes related to temperature increase. Subsequent calcite precipitation is extensive and resulted in the transformation of eolianites of the Catriel Formation in the vertical seal and coeval down dip remigration from the top of the structure. The intra-reservoir oil cracking has occurred as a consequence of an increment in the subsidence rate accompanied by an abnormally high geothermal gradient in the area.
- OSTI ID:
- 421101
- Report Number(s):
- CONF-9609255--
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 8 Vol. 80; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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