Cross-Hole Periodic Hydraulic Testing of Inter-Well Connectivity

Abstract

Harmonic (periodic) hydraulic tests can establish formation hydraulic properties during active production of geothermal wells. Field experiments were conducted in a fractured sandstone to establish the value of these tests for establishing inter-well connectivity. Sinusoidal head oscillation was induced in well and the propagation of the pressure pulse through a single fracture was measured in four observation wells. Pressure response was interpreted by non-linear regression fitting of the hydraulic diffusion equation to drawdown. Hydraulic diffusivity (transmissivity / storativity) inverted from these tests were found to be much more sensitive to local heterogeneity than traditional constant rate (Theis) tests. The method may be particularly useful for anticipating hydraulic short circuiting in fractured geothermal reservoirs.