SEQUENCE OF FOLDING AND THRUSTING OF THE PIEDEMONTE OIL AND GAS FIELDS, EASTERN FOOTHILLS OF THE COLOMBIAN CORDILLERA ORIENTAL: CONSTRAINTS FROM INTEGRATION OF BALANCED CROSS SECTIONS AND THERMAL MATURATION DATA
Mejia Hernandez, Maria Carolina 1987-
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The Piedemonte oil and gas field is located in the Foothills province of the Eastern Cordillera of Colombia, a complexly deformed fold-thrust belt of Oligocene to Recent age. The Pauto, Dele, Volcanera, and Florena thrust sheets extend over an area of 200 km2, with each thrust sheet containing a condensate field (totaling 689 MMBBL) making the Piedemonte field one of the most productive fields producing from thrust-related structural traps in the world. Previous structural interpretations of the main trap types controlling the productive reservoirs include a thrust triangle zone, an antiformal, stacked duplex, and footwall short-cut faults. Previous thermochronological studies indicate that exhumation of the Eastern Cordillera began in the Late Miocene (10 Ma) and continues to the present. The objective of this thesis is to provide an integrated structural interpretation of the Piedemonte field by creating balanced cross sections from interpretation of 3D seismic reflection data, 15,298 surface subsurface dips from dip meters, surface outcrop maps, gravity and magnetic profiles, and integration of seven vitrinite reflectance (Ro) and thermal alteration index (TAI) results from samples picked from well cores at three reservoir intervals at depths between 4 and 5 km. Three balanced cross sections across the Piedemonte field show that an important out-of-sequence thrust fault, named here the Paz de Ariporo fault (PAF), that disrupted the Florena and Pauto thrust sheets and their highly productive, sand-rich reservoir units of the Eocene Mirador, Paleocene Barco, and Cretaceous Guadalupe Formations. Measured Ro values from core samples range from 0.60 to 1.11 and TAI values range from 2.6 to 3.0 and show: 1) maturity in the 5-7 km depth range of the deeper thrust sheets of the Mirador and Barco Formation; and 2) reveal that the maximum paleotemperature reached in the thrust stack was 130°C. Three balanced cross sections across the Piedemonte field show: 1) a 7-8-km-deep detachment level of the Guaicaramo fault in the Cretaceous Fomeque formation; 2) a detachment level in the Paleocene Los Cuervos Formation of the Pauto hydrocarbon-bearing thrust sheet inside of a triangle zone; and 3) the presence of the Cretaceous Guadalupe and Paleocene Barco Formation’s sandstone reservoirs in the Florena field thrust sheet.