TECTONIC CONTROLS ON THE STATE OF STRESS FROM THE PLATE- TO RESERVOIR-SCALE

The state of stress controls all in-situ reservoir activities (e.g., fracture orientation, fluid flow, wellbore breakout, fault failure, etc.), and yet we lack the quantitative means to measure it. This issue is becoming increasingly important in light of the fact that the subsurface provides more than 80 percent of the energy used in the U.S. and serves as a vast reservoir for CO₂, nuclear waste, and energy storage. Adaptive control of subsurface fractures and fluid flow is a crosscutting challenge being addressed by the new DOE Subsurface Technology and Engineering Research, Development, and Demonstration (SubTER) Crosscut initiative that has the potential to transform subsurface energy production and waste storage strategies. A critical aspect of this initiative is improving our understanding of the tectonic influence on the state of stress. Until recently, present-day crustal stresses were widely thought to be oriented parallel to plate motion and thus controlled by plate boundary forces. However, recent stress and GPS data reveal that stresses are not aligned with plate motion in many regions (Australia, Europe, South America, Asia), suggesting a strong influence of intra-plate forces on the tectonic stress pattern. Here we combine information from the World Stress Map dataset with numerical modeling to evaluate the tectonic influence on the state of stress in a plate with good alignment between plate motion and the observed SHmax orientation (North America) and in a plate where the SHmax orientation is at odds with plate motion (Australia). The plate-scale stresses establish the background or ambient state of stress that is locally modulated at the reservoir-scale by material and structural features. Evaluation of this stress modulation and its influence on fault and fracture dynamics is facilitated by the use of high fidelity geologic framework models (GFMs) that integrate geologic data, provide numerical meshes for geomechanical modeling, and provide the means to conduct uncertainty quantification. An important utility of GFMs is their use for identifying critically stressed faults and evaluating seismic hazard associated with anthropogenic subsurface activities.