Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Long-Term Deformation Versus Stress Orientations from Borehole Breakouts in the Colombian Eastern Foothills. Distinction of Compressional and Transpressional Structural Domains
(1) Engineer and Oil Services, Bucaramanga, Colombia.
(2) Research, Ecopetrol -ICP, Piedecuesta, Colombia.
Long term deformation in the Colombian Eastern Foothills can be deduced from comparison between the trends of the Lower Cretaceous extensional structures and the Cenozoic folds. Stress orientations has been assessed by means of borehole breakouts from caliper and image logs. The quality of breakouts determined from the newer tools like image logs (UBI) from development wells is higher than the quality of breakouts from old caliper tools in exploratory wells. In general the Southern foothills (Apiay, Vanguardia, Guatiquía) has more data from old caliper tools whereas the northern study area (Cusiana, Cupiagua, Floreña) has more data from image logs. However, in some cases in the northern study area even both caliper and image logs were available in the same borehole. Although these limitations were found we interpret a possitive correlation between a northern domain with a NW-SE Shmax (perpendicular to the deformation front and the inherited structures) and a Southern domain in the study area, where based on the older caliper tools, we found a general E-W tendency for the Shmax. These finding is less robust than the Shmax from the northern study area but is concordant with a N-S orientation of the Cenozoic folds oblique to the inherited inversión structures in this segment. Based on the previous considerations we suggest that breakout data is clearly showing a northern domain where a compressional stress regime is dominant whereas breakouts together with other geological indicators would show a Southern domain south of 4°N where transpression is dominant. We hypothesize that these different domains were persistent through time and condition different structural styles and trap geometries with a narrower deformation front southwards and a broader deformation front northwards.