Fracture Orientation Analysis by the Solid Earth Tidal Strain Method

A new practical method has been developed to estimate subsurface fracture orientation based on an analysis of solid earth tidal strains. The tidal strain fracture orientation technique is a passive method which has no depth limitation. The orientation of either natural or hydraulically stimulated fractures can be measured using either new or "old" static observation wells. Estimates for total compressibility and areal interconnected porosity can also be developed for reservoirs with matrix permeability using a combination of tidal and barometric strain analysis. Data acquisition requirements are modest and no surface instrumentation beyond pressure monitoring equipment is required. The tidal method has been successfully demonstrated at a naturally fractured geothermal field (Raft River) in Southeastern Idaho and at an oil field in Western Canada. Both case studies are described.