In Situ Stress Measurements Can Help Define Local Variations In Fracture Hydraulic Conductivity At Shallow Depth

In most fractured reservoirs the natural fractures and faults provide the primary pathways<br>for fluid flow. We have used comprehensive in situ stress, fracture and flow information from a<br>number of fractured reservoirs and found that critically stressed faults (the subset of preexisting<br>faults in a reservoir which are active in today’s stress field) systematically control<br>formation permeability (Barton, Zoback, and Moos, 1995). Thus, while we agree with the many<br>researchers who have suggested that the state of stress may influence fracture transmissivity, it<br>is the critically stressed faults (not mode I tensile fractures, as is generally thought) that are the<br>most permeable fracture planes in situ. We demonstrate how this new, predictable relationship<br>between in situ stress and permeability can be used to optimize production from fractured and<br>faulted geothermal reservoirs. In environmental and geotechnical applications, the<br>identification (and prediction) of permeable fracture systems along which contaminants or<br>groundwater can flow is a primary target in most site characterization studies. We demonstrate<br>how the technologies we have developed to analyze and characterize fracture systems and<br>determine the state of in situ stress can be directly applied to shallow fractured aquifers as well<br>as reservoirs at depth.