THE GIBRALTAR DISCOVERY, NORTHERN LLANOS FOOTHILLS, COLOMBIA: CASE HISTORY OF AN EXPLORATION SUCCESS IN A FRONTIER AREA

Abstract

Ecopetrol's recent Gibraltar discovery was made in a previously little known area of the northern Llanos foothills of the Eastern Cordillera of Colombia. The structure at Gibraltar is complex and comprises a thrust stack with which are associated hangingwall anticlines providing four‐way closures (or three‐way against a sealing fault). The Gibraltar‐I well was originally drilled by Occidental in 2002. According to Ecopetrol's subsequent structural reinterpretation, this well penetrated the back limb of a fault propagation fold. This structural model was confirmed with a sidetrack well which penetrated the Palaeocene Barco Formation and demonstrated the presence of light hydrocarbons. A second objective of well re‐entry at Gibraltar was to investigate the Eocene Mirador Formation, a major reservoir unit elsewhere in the Llanos foothills, in case of missed or bypassed pay. Tests of the Mirador Formation verified the presence of high quality 57° API degree condensate that flowed at a rate of 690 barrels per day together with 44 million cubic feet of rich gas per day. The success at Gibraltar will hopefully encourage further exploration developments in this remote and structurally‐complex region.

An integrated analysis of an orogen-sedimentary basin pair: Latest Cretaceous-Cenozoic evolution of the linked Eastern Cordillera orogen and the Llanos foreland basin of Colombia

“…Reactivated Mesozoic normal faults, such as the Guaicaramo fault system in the central Llanos foothills, have been considered to be the major boundary of those structural styles. Models of inversion tectonics have been created for the southern segment of the Eastern Cordillera and Llanos foothills (Casero et al, 1997;Rowan and Linares, 2000;Branquet et al, 2002;Restrepo-Pace et al, 2004;Toro et al, 2004;Cortés et al, 2006a;Mora et al, 2006), in the central segment of the Eastern Cordillera and Llanos foothills (Colleta et al, 1990;Dengo and Covey, 1993;Cooper et al, 1995;Cazier et al, 1995;Roeder and Chamberlain, 1995;Rathke and Coral, 1997;FajardoPeña, 1998;Taboada et al, 2000;SarmientoRojas, 2001;Rochat et al, 2003;Toro et al, 2004;Martinez, 2006;Mora et al, 2006), and in the northern segment of the Eastern Cordillera and Llanos foothills (Chigne et al, 1997;Corredor, 2003;Villamil et al, 2004). Although structural models differ both in the angle and depth of detachment of the Guaicaramo fault system and in fault involvement of crystalline basement to the east, structural restorations from the axial zone of the Eastern Cordillera and Llanos Basin are similar (Fig.…”

Formation of passive-roof duplexes in the Colombian Subandes and Perú

“…2), and its most frontal structure is a monocline with no obvious east-vergent emergent fault. Based on the presence of similar structures along strike, seismic data, one exploratory well (Villamil et al, 2004), structural relief, and the principles of dip domains, we deduced that this structure is an antiformal stack (cross section in Fig. 10).…”