Transient calibration of computer model of ground water flow and transport, Piceance Basin, Colorado

Abstract

A computer model of ground-water flow (PLASM) and solute transport (TRANS) was used to simulate dewatering, injection of excess water, and recovery after abandonment from modified in-situ restoring of oil shale at Federal Lease Tract C-b [Colorado, USA]. Transient calibration of the flow model was achieved by closely matching observed fluctuations of water levels in observation wells during a large-scale, multi-aquifer, multi-well, multi-rate injection test against computer-generated head arrays. Chemical particles were moved by convection and, using random walk methods, by dispersion. The model indicates that, under proposed conditions of retort development, 1) water level recovery at the site will be rapid and result in hydraulic gradients higher than natural, and 2) ground water velocities and transport of solutes down gradient will be more rapid than predicted in previous studies.