Pressure transient analysis, case of study Ahuachapán Geothermal Field, a numerical modeling approach

Abstract

Pressure transient analysis on geothermal wells has usually been performed utilizing oil industry approaches where some of the assumptions might not be applicable due to the higher temperatures and heterogenous conditions found on geothermal reservoirs.
Through the numerical modeling approach, different parameters such as wellbore storage, formation and skin zone permeability, porosity, phase mobility, mesh, and boundary models can be explored to match the observed data depending on the geological setting.
This study applies a framework presented in the literature for the pressure transient analysis and explores the sensitivity of the parameters in three geothermal wells in Ahuachapán Geothermal Field, El Salvador, using pure water: the first well is located in the south where the reservoir fluid is saturated liquid, the second in a two-phase area in the center of the field and the last one is at the reinjection area of the field. TOUGH2 is used as a simulator and the T2GEORES library to set up the model and output visualization, in every case a radial model grid was set up and divided into three sections: wellbore, skin zone, and reservoir zone. Multiple parameters were explored to fit the pressure response. Furthermore, analytical models were applied to compare the estimated reservoir properties. The results might support making this technique a commonly used approach in the industry.