[2] The Bolivar Coast field lies in the Maracaibo dry forests ecoregion, which has been severely damaged by farming and ranching as well as oil exploitation.

[6] The large oil seeps around Lake Maracaibo were noted in the 16th century by the Spanish, who used the tar to caulk their ships and treat skin problems on livestock.

The U.S. based General Asphalt Company conducted the first geological investigations on the east shore of Lake Maracaibo but sold its concession to Royal Dutch Shell in 1912.

[7] Another major find was the 'Zumaque 1' well in 1914,[8] in the area of Mene Grande, Maracaibo Basin, about 50 miles (80 km) southeast of Cabimas (Zulia State).

The award of marginal field reactivation blocks to Occidental and Shell in 1994 marked the beginning of a new phase of international participation in the Maracaibo basin.

The deposition of rift-related rocks in the Late Jurassic marked the beginning of the sedimentary geological history of the Maracaibo Basin in structural lows or half grabens controlled by linear, north-northeast–striking normal faults.

This uplift is responsible for an increase in subsidence by the end of the Cretaceous that resulted in deposition of thick marine shale of the Colon Formation during the Maastrichtian.

In the late Paleocene and early to middle Eocene, the Caribbean plate and the northwestern margin of South America produced a complex foreland wedge filled by clastic sediments in the northeastern part of the Maracaibo Basin.

Previous geochemical studies show that the La Luna Formation is the source of 98% of the total oil reserves found in the Maracaibo Basin.

An additional 2% of the total oil reserve was derived from nonmarine coals and shales of the Paleocene Orocue Formation that are found in the southwestern part of the basin.

[10] A Santonian change in depositional environment to more oxygenated and cooler waters in the La Luna Formation (Tres Esquinas Member) suggests the advent of tectonic activity (Erlich et al., 2000; Bralower and Lorente; 2003; Parra et al., 2003; Zapata et al., 2003).

Late Cretaceous tectonic activity was possibly related to the reactivation of faults beneath the basin or regional plate convergence in western Colombia that caused abrupt changes in the paleotopography and paleoclimate and ended passive-margin conditions.

An increase in upwelling and more oxygenation of shelf waters of northern South America may be related to (1) the migration of the South American plate toward the Cretaceous intertropical convergence zone (Villamil et al., 1999); (2) an increase in freshwater runoff produced by the emergent Central Cordillera of Colombia (Erlich et al., 2003); and (3) the establishment of wet-dry cycles and submersion of paleobathymetric barriers for ocean circulation (Erlich et al., 2003).

The La Luna source rocks contain oil-prone type II kerogen and are rich in hydrogen content, with the bulk of the organic matter derived from algae and bacteria (Perez-Infante et al., 1996).

During this phase in the Late Cretaceous to Paleocene, the La Luna Formation source rock was deposited on a shallow, passive-margin, shelf-to-slope environment.

Cretaceous source rocks were buried to depths of 5 km (3.1 mi) in the north-northeastern part of the Maracaibo Basin and reached the oil window.

Strike-slip faults provided vertical pathways for hydrocarbon migration from Cretaceous source rocks (La Luna Formation) to Eocene reservoir sands.

In contrast to the Eocene, the Neogene depocenter was located in the southern Maracaibo Basin, where continental facies pinch out to the east-northeast to form major stratigraphic traps.

Deposition and distribution of ideal source and reservoir rocks were stratigraphically and structurally controlled by multiple tectonic events that led to hydrocarbon generation, migration, and accumulation.