Updated conceptual and numerical model of the Los Humeros Geothermal Field

Abstract

The Los Humeros Geothermal Field is one of the five geothermal fields currently operating in Mexico. In this study, an updated conceptual model was developed considering studies of geology, hydrology, hydrogeology, structural geology, hydrogeochemistry, geophysics, temperature and pressure data from wells, as well as previous conceptual models. To explain the behavior of this geothermal field in greater detail, as many studies as possible were integrated into the conceptual model, which required building a 3D numerical model of fluid flow and heat transfer using the TOUGH3 simulator code. The numerical model has an area of 400 km2 and a thickness of 4 km, and it is composed of 64,000, each 500 m long × 500 m wide × 100 m high. In addition, ten rock types were included in the numerical model assigning different permeability values, from 4.00E-14 to 5.28E-17 m2. Model calibration was carried out considering downhole temperature profile data from 38 wells. The obtained modeling temperatures achieved a global Root Mean Square Error (RMSE) of 35.81 °C, while for specific wells from 16.14 to 60.39 °C. The numerical model was validated under transient-state conditions during production history, using bottom pressure data of wells H-1 and H-1D from 1982 to 2006, reaching an RMSE pressure of 4.43 bar, corresponding to 3.05% of the maximum pressure. The conceptual model update developed improves previous numerical models of Los Humeros because it allows considering registered variations of bottom pressure over the almost entire exploitation history. This updated conceptual model will help locate new exploration wells and define extraction policies.