Eastern Cordillera


Petroleum geology

Hydrocarbon Evidences

Five decades of exploration history in the basin have led to the discovery of nearly 1700 MBP, 2,0 TCFG and a total of 10 fields, including Cusiana and Cupiagua and the condensed gas field, Gibraltar.

Source Rock

Two condensed sections of the middle Albian and Turonian, deposited during worldwide anoxic events are considered the main source rocks. Among them are the Simití and La Luna formations; other less important source rocks are present in the lower and upper Cretaceous sequences(Figure 2).Rocks with reduced source potential correspond to the marine shales of the Guadalupe (middle section), Chipaque, Une and Tibasosa/Fómeque formations. The main hydrocarbon source rocks contain TOC values between 1.0 and 3.0% and type I and II kerogen.

Generation and Migration

The first generation pulse occurred during late Cretaceous, but the most part of petroleum generated seems to have been lost due to lack of pre-existent traps.

A second pulse occurred from Miocene to recent. The oil migrated and was trapped in Paleogene terrestrial and transitional clastic reservoirs, as well as in those Cretaceous intervals composed of sandy and carbonatic porous rocks.

Reservoir Rock

The most important reservoir rock corresponds to sandstones of deltaic to coastal environments mainly the Une (Albian) and Guadalupe (Campanian- Maastrichtian) formations, and to terrestrial Paleogene siliciclastic units. These rocks have a wide range of petrophysical properties: average porosities between 5 and 10% and permeabilities in the order of 4-100 mD.

In the Paleogene sequence, the reservoirs, in form of fluvial sandstones interbedded with mudstones, belong to the Picacho and Lower Socha formations.

Seal Rock

The regional seal for Cretaceous reservoirs corresponds to marine and coastal shales of the Guaduas, Guadalupe (middle section), Chipaque, and Une formations. These shales are interbedded with the sandstone of the reservoirs levels. The seals for the Paleocene sandstone reservoirs consist of interbedded shales and claystones of Concentración and Socha Superior formations.

Traps

The main structural traps are reversal faults involving the basement, resulting from inversion of pre-existing normal faults (Figure 3).

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