Modelling Laramide Deformation to Predict Fracture Orientations in the Big Sand Draw, Wyoming - Part 2. Fracture Modelling

This study uses validated deformation history information to predict strain and fractures in the Big Sand Draw Anticline, Wyoming. The fracture modelling approach identifies possible fracture forming mechanisms and predicts the associated fracture orientations and intensities using geological principles and modelling. The purpose was to help identify fluid migration directions and intensely fractured areas, more conducive to fluid migration. The dominant measured fracture trend, perpendicular to the anticline axis, is best reproduced by simulated reverse slip on a deep, steep, basement fault. Deeper units have higher proportions of reproducible fractures than units higher in the stratigraphy. This supports the finding that the basement structure is the main control on fracture development and suggests there may be localised stress-field perturbations and low ambient stress at near-surface levels.The fracture sets created were analysed for slip stability and dilation tendency under the present-day stress field. The central portion of the anticline had the highest dilation tendency values in the reservoir interval. This is an area where joints and shear planes, produced from basement involved deformation are very prevalent. The results of this study have important implications for the positioning of future CO2 injection sites and production strategies for the BSD Anticline.