Evaluation of subsurface fracture geometry using fluid pressure response to solid earth tidal strain

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Report: Evaluation of subsurface fracture geometry using fluid pressure response to solid earth tidal strain

Abstract
The nature of solid earth tidal strain and surface load deformation due to the influence of gravitational forces and barometric pressure loading are discussed. The pore pressure response to these types of deformation is investigated in detail, including the cases of a confined aquifer intersected by a well and a discrete fracture intersected by a well. The integration of the tidal response method with conventional pump tests in order to independently calculate the hydraulic parameters of the fracture-formation system is discussed. How advanced spectral analysis methods, coupled with correlation analysis can be used to extract the tidal response signals from the pressure record is shown. Uncertainties in the signals are estimated using various information-theoretic methods in order to place a confidence level at which we can safely assume that the measured signal is indeed of tidal origin. A detailed case study of the method carried out at the Raft River Geothermal Reservoir in Idaho is presented. All of the analyzed tidal data is presented and the results of the computed fracture orientation using the solid earth tidal strain approach are compared with the extensive field work carried out at Raft River over the past decade. The direction that future work in the continuing development of this technology should take is discussed, including: (1) the present need for an expanded data base for the confirmation of present tidal strain response models, and (2) improvement in response models.

Authors 
Hanson and J. M.  








Published 
DOE Information Bridge, 9/1/1984





DOI 
10.2172/6281721


 

Citation

Hanson, J. M.  . 9/1/1984. Evaluation of subsurface fracture geometry using fluid pressure response to solid earth tidal strain. (!) : DOE Information Bridge.


Related Geothermal Exploration Activities
Activities (1)


Areas (1)
  1. Raft River Geothermal Area
Regions (0)