Tectonic and Sea Level Control in Plato Basin (Lower Magdalena Province, Colombia)

Mario Suárez and Lina Rendon
Exploration, Ecopetrol, Bogotá, Colombia

The objective of this paper is to show the relationship between tectonosequences and marine sequences developed in an active margin and the implications for reservoir prediction.

During the Paleogene the Plato basin was filled mainly by marine sediments with syntectonic deposition related to extensional listric faults responsable of the creation of the basin as a mega half graben. During the Neogene syntectonic activity stops and the whole basin became deeper by regional tectonic subsidence with dominant deep marine deposition.

A regional seismic interpretation of 13 2nd order stratigraphic units was conducted in the Plato Basin. In the depocenter significant tectonic unconformities separating these units were not developed while in the paleohighs sorrounding the basin ocurred important gaps due to local tectonic activity. The most preserved sedimentary record can be seismically observed in the depocenter reaching about 30.000’ of tertiary rocks.

Internally each one of these tectonosequences can be composed regularly by two to four marine sequences indicating that after te creation of a 2nd order tectonic boundary the basin increase accomodation space and the sea level control is dominant until a new tectonic pulse creates a new second order boundary.

This mix of tectonic and eustatic control of deposition can be recognized in active margins and differenciated in the stratigraphic framework. As a result two different scales of reservoir prediction can be approached. Regionall reservoirs distribution is controlled by tectonics with thick marine sandstones sorrounding the main paleohaighs or carbonates deposited directly over the paleohighs. Locally third order slope fan and basin floor fan deposition is controlled by dominant control of eustacy representing a new play to be explored in the basin.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas