GEOL Dissertation Comprehensive Exam - Essam SaeidFriday, April 28, 2017 - 9:30am
Garzón Massif basement tectonics: structural control on evolution of petroleum systems in Upper Magdalena and Putumayo basins, Colombia
Well, seismic, gravity, and magnetic data were used to generate a stratigraphic and structural framework for the Garzón basement uplift, and flanking structures in the Upper Magdalena Valley (UMV) and Putumayo Basin, Colombia to determine the role of thin-skinned and thick-skinned deformation on oil generation and migration versus trap formation synchronization.
1D basin modeling shows that no source rocks in the Putumayo Basin are presently buried deeply enough to produce the oil and gas observed in the basin’s reservoirs. Based on retrodeformed structural models and 1-D well modeling, we propose that “thin-skinned thrusting preceded the main hydrocarbon expulsion event (10 Ma), followed by Andean basement uplift (6 Ma), formation of the Topoyaco monocline and the Garzón basement thrust fault. The hydrocarbon kitchen for the critical moment at 10 Ma was located 80 km to the northwest of Topoyaco under the present Central Cordillera or UMV. Late Oligocene to Mid-Miocene rock uplift of the Central Cordillera deepened the foreland basin, creating migration pathways southeastward in the Villeta Formation and further north over the paleo-Garzón Massif in the Pepino Fm to the Putumayo Basin.
The Garzón fault, a reactivated reverse fault, thrusts (12 to 17 degrees) Precambrian granitic rocks over Tertiary sediments of the UMV. The new low-angle Garzón thrust fault model predicts that Cretaceous reservoir rocks in the footwall anticline extend an additional 12 km east of present drill sites. Retrodeformed 2D regional models indicate at least 22 km of shortening and 7 km of rock uplift on basement thrust faults in the last 6 Ma. This was preceded by approximately 43 km of shortening by southeast-verging thin-skinned imbricate thrusting (~9-16 Ma).
Intense fracturing is observed in the Topoyaco basement monocline from the near-surface to depths of over 2000 msec (3.5 km). The high level of fracturing permitted freshwater flushing and oil biodegradation and hydrocarbon escape. In contrast, the Miraflor-1 well, located just southwest of the Topoyaco block, tested light gravity oil and is sealed from groundwater flushing and biodegradation by a backthrust on its northwest flank.