Sistemas Petroleros De Cuenca Austral, Argentina Y Chile

Petroleum systems of Austral Basin, Argentina and Chile. The Austral Basin is located in the southernmost region of South America, with oil and gas production from onshore and offshore. The evolution of the basin includes the following tectonic phases: rift (Jurassic — Early Cretaceous), sag (Early Cretaceous) and foreland (Early Cretaceous to Cenozoic). The stratigraphy of the basin includes volcanic and volcaniclastics in the synrift succession, and a mainly fine-grained siliciclastic marine and continental sag and foreland section. Considering present characteristics as the structural style, stratigraphy and oil/gas distribution, five oil provinces can be differentiated: Platform area, North of the Santa Cruz River area, Intermediate area, Basin Center and Fold Belt area. These regions present different stages of exploratory maturity and potential. The evaluation of the geochemical characteristics of the Inoceramus Inferior Fm. allowed the differentiation in areas of distinctive source potential. The southern part of the intermediate zone appears to have a slightly better source potential than the northern half. The platform has in general no potential, due to the low total organic contents and the terrigenous dominated organic matter evidenced by the low values of hydrogen index. The<br>source levels of the Inoceramus Inferior Fm. (Lower Member of Rio Mayer Fm.) were deposited contemporaneously to the Springhill Fm. sands during successive cycles between the Late Jurassic and the Early Cretaceous. The general transgressive pattern<br>moved from the SW towards the NE area of the basin. The areal variability of source potential of Inoceramus Inferior Fm. and its equivalents is assigned to the differences in conditions during the sedimentation of the sedimentary cycles, like paleoecology. The deposition of Inoceramus Inferior Fm. occurred on a platform, probably under dysaerobic to anaerobic conditions. Organic rich levels seem to be related to the presence of physical barriers that restricted the basin and produced stages of water stratification. The restricted sea developed in part during tectonic instability related to the opening of the South Atlantic Ocean. During that period a general transgression occurred allowing the deposition of the source shales and sandstone reservoirs of the Springhill Fm., associated to warm and humid climatic conditions.