Oil Distribution in the Carbonera Formation, Arenas Basales Unit: A Case Study in the Quifa and Rubiales Fields, Eastern Llanos Basin, Colombia

Dasilva, Angel¹; Gomez, Yohaney; Villa, Maria A.; Yoris, Franklin; and Morales, Diego
¹[email protected]

The Eastern Llanos Basin has almost 70% of the reserves in Colombia and the Rubiales and Quifa fields are the largest heavy oil fields found in this basin showing a production near to 250,000 stbl/day at November 2012.

Continuous drilling activity has allowed to significantly increasing production, but it has demonstrated that there are some stratigraphic issues that are affecting the oil distribution and consequently, the drilling success in both fields.

The main oil accumulation in the area occurs in the Carbonera Basal interval or "C-7" unit of Carbonera Formation, informally known in the area as "Arenas Basales", it has been deposited in a varied succession of fluvial environment genetic units, which hold oil producing columns between 7 and 60 feet. In the Rubiales and Quifa fields, the main trapping mechanism is a combination between structural and stratigraphic features. The proper structural traps are formed by normal faults dipping up to the basin. The stratigraphic features comprise diverse fluvial regimes in which channel bars are stacked vertically in successive fluvial plains, which in turn vary laterally. Using 2D seismic information and well data, it has been possible to identify two major seismo-stratigraphic units that represent the oil reservoirs. The "Arenas Basales" identified at the northern part of the Quifa Block is lithostratigraphically equivalent to the "Arenas Basales" in Quifa Southwest and Rubiales fields, but chronostratigraphically it corresponds to an older genetic unit. The presence of more than one oil water contact in some wells confirms the existence of different reservoir flow units along these fields.

Changes in lateral continuity of facies can be correlated showing muddy facies at one side and sandy facies on the other side, all of this to the scale of the sub-areas in Quifa Block. The implementation of 3D seismic inversion in a recently acquired seismic volume may help to identify facies changes and oil distribution in the "Arenas Basales", increasing the drilling success in the Rubiales and Quifa fields.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013