Ernst Huenges

Production data from the Los Humeros geothermal field in Mexico are used to develop a forecast method for operation of the field in the future. This method supports understanding the limitations of sustainably exploiting a geothermal reservoir. Using such forecasts, fluid extraction could be scheduled in order to fulfill the steam demand of the installed capacity. Moreover, the forecast of the extraction can diminish the commercial risk involved and therefore clear the way for new investments. Herein, we determined the total extracted heat from the Los Humeros geothermal system, with the aim to forecast the next phase of fluid extraction. We took the information from 29 producing wells to analyze their historic geothermal fluid production. From their statistical distribution of data, we estimated the amount of extracted fluids for a future phase. The size of the heat reserve previous to exploitation was calculated from the forecasted and the extracted heat. Thus, the recovery factor of the system was calculated as the ratio of the accumulated production of heat and the initial heat in place. The general recovery factor for 60 years of production was calculated as 37–44%. Due to the heterogeneity of the system, this study conducted individual assessments. The forecasted heat extraction for the next 30 years of production, amounts to 580 PJ assuming a constant extraction rate between 6 and 56 ton·[h]⁻¹ depending on the particular well. The results of this study potentially complement the existing models of the geothermal exploitation and offer an estimation of the future production of the Los Humeros, which could be a good basis for decision-making and management of the site.

Summary During production of geothermal brine at the Groß Schönebeck research site, large and heavy solid particles accumulated within the cased reservoir interval of the production well. A wellbore obstruction at a depth of approximately 4100 m (13,452 ft) was caused by copper-, barite-, lead-, and iron-mineral precipitates with a size of up to 1 cm and elongated coating fragments from the production tubing with a length of up to 10 cm. After a failed reverse-cleanout operation by use of 2-in. coiled tubing (CT), lifting the fluid column within the drillstring (DS) was considered to be the most cost-efficient option to clean out the wellbore while simultaneously minimizing fluid invasion into the reservoir. Here, preliminary considerations for the operation and field observations are presented together with a monitoring concept. The field data are used to calibrate a hydraulic model that is then applied to understand hydraulic processes downhole. On the basis of the hydraulic considerations, aspects to optimize the cleanout efficiency are discussed.