Dual Porosity Models of a Discharge Test

Abstract

The research reported here is part of a general study aimed at determining when dual-porosity models should be preferred ahead of single porosity models for modelling geothermal systems. A discharge test of well, SKG9D, in Fushime, Japan, was simulated using both single and dual porosity (MINC) models and inverse modelling was used to estimate parameters such as permeability, porosity and initial pressure and gas saturation. The forward simulations were carried out with AUTOUGH2 (Yeh et al., 2012), a modified version of TOUGH2 (Pruess et al., 1999) while the inverse problem of determining the best-fit parameters for the models was solved using PEST (Doherty, 2013). The data used for calibration were flowing enthalpies and pressures measured daily for 139 days. The results were compared for a single porosity model and various dual porosity (MINC) models with the aim of determining whether or not one type of model clearly fitted the data better than the others. All the dual porosity models used to simulate the discharge test of well SKG9D were able to reduce the objective function to a lower value than that for the single porosity model.