Abstract

There is a significant lack of data about present day stress fields in Antarctica. Stresses provide valuable information data about the forces acting on the plates. In Antarctica, stresses may be related to ridge forces such as rifting and/or uplifting, to ice loading/unloading related processes,... Show moreThere is a significant lack of data about present day stress fields in Antarctica. Stresses provide valuable information data about the forces acting on the plates. In Antarctica, stresses may be related to ridge forces such as rifting and/or uplifting, to ice loading/unloading related processes, or both. This project involves the study of drilling induced fractures from core recovered in the Victoria Land rift basin of Antarctica. Drilling induced fractures form ahead of the drill bit during drilling from stress imbalances due to the removal of excess weight pressure around the rock. Because horizontal stresses strike parallel to the planes made by drilling induced fractures, they can be used to measure modern day stress fields. Whole core images obtained during core logging by digitally scanning the outside of the core are stitched into longer intact intervals. Drilling induced fractures in the core are ‘picked’ in order to obtain their azimuth. Magnetically oriented acoustic images of the inside of the drill hole are then compare side by side with the stitched whole core images and visually scanned for matching features. Once the same set of fractures is found in the core and the borehole is then possible to rotate to core images to match the orientation of the borehole image. This will result on a core image with all the fractures in that interval re-oriented to true north. This final orientation of drilling induced fractures in the core will thus provide the direction of maximum horizontal compressional stress in this area. Show less