Bradys (Nevada) InSAR Anomaly Evaluated with Historical Well Temperature and Pressure Data

Abstract

In 2005, Oppliger et al. demonstrated a new approach for modeling satellite interferometric synthetic aperture radar (InSAR) observed surface deformations in terms of 3-D subsurface volumestrain rate (change) distributions using the Bradys geothermal field as a case study. A key result was the recognition of volume-strain in shallow lateral horizons to the northwest of the Bradys field indicative of thermal fluid outflow. The model also postulated that the volume decrease for a distance of approximately 5 km away from the main Bradys fault splays could be attributed to temperature and pressure decreases at approximately 1.5 km depth. The temperature and pressure log data presented here validate the presence of a shallow, laterally short outflow plume near the Bradys fault and a zone of decreased temperature and pressure away from the fault at about 300 to 600 m. While shallower than the postulated 1.5 km depth, that depth was modeled without any physical constraints on pressure and temperature in the reservoir. These data were only used to validate the model, which could now be calibrated given the close match between observed and modeled results.