--> Petroleum Systems of the Tayrona-Rancheria Basin, Offshore Guajira Peninsula, Colombia


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Petroleum Systems of the Tayrona-Rancheria Basin, Offshore Guajira Peninsula, Colombia


The Tayrona-Rancheria Basin (TRB) is a large (~29,000 sq. km) forearc basin located offshore of the Guajira Peninsula, Colombia, that contains up to 5 km of Cretaceous to Recent sediments. Historical drilling activity in the TRB has favored the landward portion of the basin, resulting a commercial discovery of the 7 trillion cubic ft of gas (proven reserves) Chuchupa/Ballena biogenic gas field. However, a recent deepwater exploration well (Orca–1, 2014), located on a basement high ~40 km off the shore of the Guajira Peninsula, was announced as an exploration success (gas). The origin of the gas (thermogenic or biogenic) has not been released. Using an extensive database of wells, industry seismic data, and gravity/magnetic data, we identify the necessary elements for a working thermogenic hydrocarbon system in the TRB. These elements include (1) large structural traps (greater than 500 sq. km) present in water depths ranging from 2400 to 2700 m, (2) reservoir intervals composed of distal, deepwater Miocene-Pliocene turbidites and associated basin floor fans, and (3) sealing units of hemi-pelagic shale imaged throughout the area as widespread, contiguous low-amplitude events. We propose the existence of deep, oil-prone, Upper Cretaceous sediments, as well as organic-rich, gas-prone sediments from Miocene-Pliocene deposition as potential source rocks. These elements are integrated into a detailed petroleum systems model for the basin. A range of possible heat flow scenarios are incorporated into the model to understand better necessary conditions for generating thermogenic hydrocarbons. Ultimately, a recoverable hydrocarbon resource estimate for the basin is provided, which will be of significance for future exploration efforts.