Hydrocarbon generation models along the basal detachment of the Andean subduchon zone in Northern Ecuador to Southern Colombia

Abstract

Numerous fluid vents and hydrocarbon seeps of a thermogenic origin have been reported in the middle and lower slope of the Northern Ecuodorean - Southern Colombian (NESC) Pacific margin. These hydrocarbon manifestations ore frequently located over the traces of faults connected with the basal detachment of the subduction zone, very far (80km) from the hydrocarbon kitchens formed along the axis of the NESC forearc basins. In some subduction zones, the origin of these types of thermogenic seeps is related to the generation and migration of hydrocarbons along the subduction zone d6collement. To test the possibility of generation of hydrocarbons in the NESC decollement, 2D Time-Temperature Index Arrhenius equation (TTIArr) numerical models were constructed in four regional cross sections. The results suggest that along the top of the subducting plate, favorable conditions exist for oil and gas generation below depths of 10 km , with subtle variations of the oil and gas depths of generation, due to lateral changes in the thermal structure of the margin. The available geophysical data support the presence of favorable structures to trap the hydrocarbons generated along the top of the subducting plate {low velocity zones), and/or the seepage of fluids to the sea floor along the middle and lower slope of the NESC margin.