The La Hocha High and associated oil fields (Upper Magdalena Valley, Colombia): A new 3D structural model based on subsurface data

Alto de La Hocha e campos petrolíferos associados (Vale do Alto Magdalena, Colômbia): Um novo modelo estrutural 3D baseado em dados de subsuperfície

Abstract

The La Hocha High (LHH), in the Upper Magdalena Basin of Colombia, consists of a crystalline basement overlain by a Triassic to Neogene sedimentary sequence up to 9 km thick. The San Jacinto Fault (SJF), is a dextral NE-SW striking positive-flower structure with subordinate Riedel shears which strikes N-S with subvertical to high dip to the west. It separates two main structural domains: (i) the La LHH and the Tesalia syncline in the western hanging wall block; and (ii) an eastern footwall block with a synclinorium with three north-south trending en echelon anticlines (shows a recumbent, tight, Z-shaped anticline dipping between 45 and 90° to the west), La Cañada and La Cañada Norte oil fields. The LHH has undergone at least five pulses of transpression between the Maastrichtian and present. Variations of the strike orientation have resulted in local flexural segments that are more transtensive to the right and transpressive to the left. Previous structural interpretations based on 2D balanced sections suggested stacking of thrust sheets detached in the basement as a result of orthogonal plate convergence. However, this new 3D interpretation, based on surface geology, well data and a recent 3D seismic survey, shows clear evidence of dextral Andean thrust components on pre-existing normal faults that controlled Triassic-Jurassic rifting.