--> ABSTRACT: The Molino-Tertiary(!) Petroleum System in the Southern and Central Altiplano and Adjacent Eastern Cordillera, Bolivia, by Oscar Aranibar, Miguel Cirbian, Suhas Talukdar; #91020 (1995).

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The Molino-Tertiary(!) Petroleum System in the Southern and Central Altiplano and Adjacent Eastern Cordillera, Bolivia

Oscar Aranibar, Miguel Cirbian, Suhas Talukdar

The southern and central Altiplano and the adjacent Eastern Cordillera of Bolivia is a frontier region for petroleum exploration. Occurrences of good to excellent type I and type II oil source rocks within the Upper Cretaceous Molino and Chaunaca Formations and genetically related oil seeps indicate the existence of a known petroleum system in the region. It is named as the Molino-Tertiary(!) Petroleum System based on the more important Molino source rocks and the likely Tertiary sandstone reservoirs.

Burial history-maturity diagrams suggest oil generation, migration, and accumulation occurred in the southern Altiplano during late Eocene-early Miocene time (44-10 m.y.b.p.), and in the central Altiplano during early-middle Miocene time (21-12 m.y.b.p.). Sandstone reservoirs are probably present in the Eocene-early Miocene, Potoco/Tiahuanacu Formation, the late oligocene-early Miocene San Vicente and the equivalent Tambillo Formations, and the middle Miocene-early Pliocene Caquiaviri Formation. Possible seal rocks are represented by shales of the Santa Lucia (Paleocene) and the Potoco/Tiahuanacu Formations, shales and evaporites of the San Vicente/Tambillo Formations, and the shales, evaporites and silicic volcanics of the Miocene-Pliocene formations. Structural traps in the Potoco/Tiahuanacu Formations probably formed primarily during the main early-middle Oligocene compressive deformation. Combined stratigraphic- structural traps in the Sam Vicente/Tambillo Formations might have developed during less intense Miocene deformations. Stratigraphic traps are also expected in the San Vicente/Tambillo Formations and in the Caquiaviri Formation.

The critical factors of a petroleum system including a sufficient volume of effective source rock, favorable timing of trap formation in relation to timing of oil generation/migration, and the existence of sealed reservoirs within the oil stability range, all appear to be present in the eastern fringes of the southern and central Altiplano.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995