Petroleum generation and accumulation in the Golfo San Jorge Basin, Argentina: a basin modeling study

Abstract

The Golfo San Jorge Basin, located in Patagonia, is very important for the oil and gas production of Argentina. In spite of the long history of exploration and production, few geochemical studies were performed until now. For this study, a set of possible source rocks was analyzed by organic geochemical and petrographical methods. The samples of the Pozo D-129 Fm. range from mature to overmature, and contain from less than 0.5 to 2.45% TOC. There is some evidence indicating an algal origin of the more hydrogen-rich kerogen present in part of the basin. Almost all the samples of Pozo Anticlinal Aguada Bandera and Pozo Cerro Guadal Fm. are overmature. TOC values range from less than 0.5 to 2.5%. The maturation of source rocks and generation, expulsion and migration of hydrocarbons was evaluated by means of 1D and 2D basin models. The 1D models constructed for the western part of the basin and 2D models applied for the eastern part both indicate maximum burial in Miocene times. The thickness of the Tertiary at times of maximum burial ranged from 1000 to 1500 m and the generally small Tertiary thickness now present in the fold belt region is assumed to be the result of erosion. The main tectonic inversion took place in the Late Neogene. The models strongly suggest that a magmatic event between 20 and 30 Ma, combined with the maximum burial at Miocene times produced a very important pulse in hydrocarbon generation within the major part of the basin. Dated intrusive and extrusive magmatic rocks extended all over the basin account for this period of elevated heat flow. Migration pathways are extensively discussed for the 2D model. Probably, major faults acted as important conduits for petroleum.