Assessment of the northern part of the Los Azufres geothermal field, Mexico, by lumped parameter modelling and Monte Carlo simulation

Abstract

The Los Azufres geothermal system is located in the State of Michoacán 80 km east of the city of Morelia and 16 km northwest of Ciudad Hidalgo. It was explored in the mid 1970's and it has been in development since then. At the present time, the Los Azufres is generating 188 MWe and in order to increase its potential it is needed to update the assessment of the area. In the present work, the actual potential of the northern part of the Los Azufres is assessed. The formation temperature of the northern part of the Los Azufres geothermal field was estimated and the thermodynamic parameters were gathered to estimate the potential energy of the field using Monte Carlo simulation. The result shows that there is a 90% probability that the field can sustain a production of 290 MWe for a period of 20 years, 230 MWe for a period of 25 years and 190 MWe for a period of 30 years. To assess the consequences of such a production increase on the pressure of the Los Azufres system another method called lumped parameter modelling was used. To account for the reinjection, tracer information is used to estimate the amount of water that is recharging the production zone and by subtracting that amount from the total production we get the effective production that is going to be used in the model. The results of the lumped parameter modelling predict a substantial drawdown in pressure for production scenarios of 400 kg/s and 500 kg/s equivalent to approximately 125 and 155 MWe generation, respectively. Comparing the outcomes with previous works, lower values are obtained for the power capacity of the area, which is mainly due to the area chosen being smaller. Also the conservative values used to determine the effect on the production due to injection could cause an overestimation of the pressure response of increased production.