ABSTRACT: Geology of the Northwest Flank of the Venezuelan Andes and its Future Exploration Possibilities

Tito Boesi

On the northwest flank of the Venezuelan Andes, located southwest of the Maracaibo basin, an extensive exploration campaign is being done in an area covering 230 × 50 km.

The geological and seismic information indicate an igneous-metamorphic basement containing both Paleozoic and Triassic-Jurassic rocks. The Cretaceous, the main exploration objective, consists of clastic sediments and carbonates in the Lower Cretaceous La Luna Formation, the type II source rock in the area. A secondary objective is a Paleogene clastic sequence containing types I and HI source rocks. The Neogene is mostly a molasse deposit that reaches its maximum thickness in the Bobures trough, adjacent to the northwest Andean Flank. The evolution of the trough can be related to both the Miocene Orogeny and to the hydrocarbon habitat.

Structurally, the basement consists of Cretaceous and Paleogene rocks thrusted on top of younger sediments in the trough. The major thrusts are located in the northern sector of the study area in front of the La Culata range. To the south, smaller thrusts exist near the towns of Seboruco and La Fria.

Toward the beginning of the Late Miocene orogeny the La Luna Formation was located at the oil window. After the orogeny, the zone of maturity was restricted to the trough which became gas prone as the hydrocarbons migrated to the flank where some of the oil is believed to have escaped. At the major thrust, granitic rocks constitute the seal, and in the remaining structures the shaly formations act as impermeable layers.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990