Titel: Crustal structure and margin configuration of the La Baja Guajira basin, Colombia: regional 2D seismic reflection interpretation, gravimetric and thermal modelling

Leidy Castro-Vera1,2, Ralf Littke1, Stefan Back1, Rocío Bernal-Olaya3

1RWTH Aachen University, Germany; 2Grupo de investigación en Ciencias de la Tierra y Energía, Amonite SAS, Colombia; 3Universidad Industrial de Santander, Colombia

Veranstaltung: GeoKarlsruhe 2021

Datum: 2021

DOI: 10.48380/dggv-xzq3-5766

The La Baja Guajira Basin (LBGB) is the primary gas-producing region of Colombia and represents South America's northernmost prolongation. This study presents an analysis of regional 2D-seismic reflection data of LBGB integrated with borehole and gravity information. The deepest basement in the study area occurs in the northwestern offshore. This depocenter is oriented NW-SE. In the basin, four fault groups occur: 1) NW-SE-striking basement normal faults; 2) strike-slip faults; 3) inverted normal faults, and 4) local thrust faults. Prominent bottom simulating reflectors (BSRs) are present in the NW deep-water areas.

2D gravity modelling was used to comprehend the basin's geometry and basement type. It indicates that the crust under LBGB is best simulated with rocks of continental nature. 1D petroleum system modelling was applied to reconstruct and evaluate the basin's burial and thermal history. Modelling results show that the study area experienced two episodes of rapid tectonic subsidence (lower Middle Miocene, Late Miocene). During the Lower and Middle Miocene, sediment input into the LBGB was from east to west. In the Late Miocene, the Andean uplift provided an additional and significant sediments contribution from the south. A period of erosion due to uplift is evident in the northern area between the uppermost Middle and Upper Miocene. From the Pliocene to recent, relative tectonic quiescence is observed. Sediments in well Mero-1 (southern offshore) were subjected to high temperatures causing Middle Miocene source rocks to reach maturation indicated by 0.69 %VRr values; however, greater depths and temperatures are required for hydrocarbon generation.

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