Shallow Temperatures and Thermal Regime in the Hydrocarbon Province of Tierra del Fuego

Abstract

A suite of shallow (< 2 m deep) thermal measurements across the San Sebastian oil and gas field, northeastern Tierra del Fuego, indicates at least a 200 mWm-2 (5 HFU) thermal anomaly over the field. The anomaly appears to be of subsurface origin and, due to its magnitude, must be caused by a localized discharge of deep groundwater. A single published heat flow value and deep bottom hole temperature data for the area suggest a regional heat flow that is at least 20 mWm-2 (0.5 HFU) higher than the world average for similar tectonic provinces (post-Precambrian non-orogenic). Maturation level estimates based on the heat flow and burial history of sediments suggest considerable lateral migration (at least 100 km) of hydrocarbons from deeper in the Magellan basin. From estimates of the timing of possible oil generation, minimum average migration velocity is within 1 or 2 orders of magnitude of the groundwater velocity required to cause the local and regional heat flow anomalies. This suggests that groundwater moving from deeper in the Magellan basin might simultaneously transport hydrocarbons and heat to the area. Volume flux estimates require that hydrocarbon concentrations significantly greater than possible via aqueous molecular solution.