Stratigraphic Control of Incised Valleys in a Heavy Oil Accumulation in the Eastern Llanos Basin, Colombia: An Opportunity for a New Field Development
Lugo, Jairo M. and Isea, Andreina1
The Eastern Llanos Basin in Colombia has been the subject of an intense exploration activity in the last 5 years, searching for new heavy oil discoveries, as analogues of the Rubiales field that could extend to the southwest in this part of the basin.
The results of the exploration drilling activity during this time have shown that there is a strong stratigraphic control on these accumulations, which is associated to the occurrence of fluvial deposition along incised valleys and the pinch-outs of the tertiary sedimentary units updip against basal foredeep unconformity. This paper presents how the configuration and distribution of these incised valleys can control the reservoir distribution and reservoir quality in this part of the basin.
Around 900 km of 2D seismic data, and electric-log and core analysis from 20 exploration and stratigraphic wells have been used to map the distribution of several incised valleys and the occurrence of the reservoir facies within the Basal Sands of the C-7 Unit of the Carbonera Formation. The framework for the analysis has been defined by correlating top reflectors of the Basal Sand
Unit and bottom reflectors associated to the foredeep unconformity which truncates the Paleozoic units, as well as reflection configurations and petrofacies analysis. The interpretation of this data indicates that these valleys were filled by a series of stacking fluvial deposits, predominantly oriented in northwest-southeast direction, which clearly define and control the distribution of the reservoir accumulations in this part of the basin.
However, although the current data has helped to understand the channel orientation and their width and thickness, there still are some uncertainties concerning reservoir extension and complexity in this area. The acquisition of 3D seismic and special inversion processing will help to establish reservoir lateral continuity and degree of compartmentalization, which will help to improve reservoir development plan and to identify new exploration opportunities in the area.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013