The Cohembi Field: A New Play Emerging in the Putumayo Basin of Colombia
Harris, Richard G.1; Monroe, David; Rambold, Patrick; Christiansen, Randi; Street, Eric; Pereira, Carlota; and Paz, Heiman
The Cohembi pool lies within the Suroriente block located in the Putumayo basin of Colombia, directly north of the border with Ecuador. Suroco Energy holds a working interest in this block contract held jointly in consortia with Ecopetrol and Vetra Energy. The Cohembi pool was discovered by the Cohembi 1 well, drilled on a footwall structure of a reverse fault for Cretaceous Villeta U and T reservoirs in a conventional structural configuration in 1989. The Villeta U and T were wet, but 9 feet of sandstone pay was discovered in the Villeta N, lying at the top of the Villeta, below an important unconformity between the Cretaceous and Tertiary sections. The N sand appeared as a thinner secondary reservoir "discovery", one which is the basis of a major new oilfield.
The Cohembi 1 well was produced intermittently from the Villeta N until 2009 when the consortia group recognized that this single well discovery was connected to a much larger oil resource than initially estimated. Following the acquisition of 3D seismic, extensive geophysical modelling and a play concept developed through a regional core and log analysis study, a two well appraisal drilling program commenced in 2011. Both wells were successful and led to the commissioning of an initial development study which concluded in early 2012. Since that time, numerous development wells have been drilled and the field is currently estimated to have greater than 100 million barrels of discovered oil initially in place. The field has several peculiarities that provided clues to its potential and how it could be developed to maximize oil recovery; the reservoir is significantly over-pressured; it does not appear to have aquifer support and it has a reservoir that is 99% quartz with permeability that often exceeds a darcy or more. Consequently, Suroco and its partners have commenced the first Villeta N sand waterflood development in the Putumayo Basin. Extending this new understanding of the reservoir distribution of the Villeta N sand to the regional database of wells and seismic in the Putumayo basin strongly suggests that the Cohembi pool could be the foundation of a prolific new play trend in Southern Colombia.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013