Applications of FLASH – A Program for Flow-Log Analysis of Single Holes

Borehole-flow logs obtained with flowmeter, fluid dilution, or tracer tools can be used to delineate flow zones under ambient and stressed conditions.   In addition, flow logs and open-hole water levels under ambient and stressed conditions can be analyzed to estimate transmissivity and far-field heads of individual zones in the borehole using analytical or numerical models.  

The USGS computer program, FLASH (Flow Log Analysis for Single Holes), provides an easy-to-use utility for the quantitative analysis of flow logs collected in single boreholes.  The code is based on a multi-layer, analytical solution for steady-state radial flow to a single borehole.  FLASH provides a simple graphical user interface (GUI) for calibration of an analytical borehole-flow model and for estimation of flow-zone transmissivities and far-field heads. Flow zones can be discrete fractures, fracture zones, or aquifer layers. FLASH is embedded within a Microsoft Excel spreadsheet and uses Visual Basic for Applications (VBA) routines to invoke the Excel solver for automated parameter estimation. Optional constraints on head and transmissivity as well as regularization can be used to obtain reasonable estimates of the solution. Here, we present the FLASH code and discuss its application to data from several sites in fractured and porous-media aquifers.