Determination of principal stress orientations from wireline logging caliper data and borehole images in deep drilling

摘要

During IODP Expedition 319, a deep ocean borehole was drilled in the center of the Kumano forearc basin in the south-west Japan Nankai subduction zone, as a part of the scientific ocean drilling project called NanTroSEIZE. The borehole penetrated the Kumano forearc basin sediments and the underlying accretionary prism. In a depth range from approximately 700 mbsf (meters below seafloor) to the target depth of 1600 mbsf, wireline logging was carried out including caliper and the FMI borehole images. I used both the borehole images and caliper data to identify borehole breakouts that could be interpreted in terms of principal horizontal stress orientations. The results of stress orientaion determination and thier scien-tifc interpretations have been published (Lin et al., 2010). This report is focused on the method of stress orientation analyses based on borehole breakouts.