Neogene-Quaternary evolution of the La Baja Guajira Basin, Colombia: burial and thermal history with implications on petroleum systems

The La Baja Guajira Basin is the primary gas-producing region of Colombia. This study analyses regional 2D-seismic reflection and borehole data to better understand the Neogene-Quaternary events controlling the basin.

The basement’s configuration controlled the sedimentation, and its structural depressions formed the main depocenter (Tayrona Sub-basin). The basement is a pre-rift sequence that displays an abrupt westward deepening of its top from 0.8 km to 12 km depth over 30 km.

Two phases of rifting occurred during the Early Miocene: 1) half-graben formation along onshore and proximal offshore areas, and 2) extension migrated westward and formed the necking domain along the distal offshore area.

From the latest Early Miocene to the Early Pliocene, subduction of the Caribbean Plate underneath South American Plate influenced the basin’s offshore area by compressional deformation associated with inverted reactivation of larger normal basement-rooted faults.

During the Middle Miocene, the extension had ceased, sediments filled significant residual accommodation space, and the proximal area remained quieter favouring the deposition of clinoforms that prograded westward until the Quaternary.

Two exhumation pulses (Middle Miocene and Early Pliocene) of adjacent areas resulted in increased subsidence and sedimentation rates, which led the rocks to reach maximum temperature peaks and burial depths. In the Late Miocene, a period of erosion affected the northern proximal areas.

From Late Pliocene to Pleistocene, sea-level changes dominated over tectonism. Ongoing hydrocarbon generation can be expected in the south. High sedimentation rates calculated can lead to microbial gas generation and favour the preservation of biogenic gas accumulations.