The worldwide experience of reinjection in geothermal fields is reviewed. Information from 91 electric-power producing geothermal fields shows that: a reinjection plan should be developed as early as possible in field development and it should be flexible as it is likely to change with time. The optimum reinjection strategy depends on the type of geothermal system. For vapour-dominated systems which can run out of water reinjection should be infield. While for hot water and liquid-dominated two-phase systems (low-enthalpy and medium-enthalpy) reinjection is likely to involve a mix of infield and outfield injection. In general infield reinjection provides pressure support and thus reduces drawdown and the potential for subsidence, whereas outfield reinjection reduces the risk of cold water returning to the production area. Deep reinjection reduces the risk of groundwater contamination and ground surface inflation. The proportion of infield to outfield reinjection and the location (deep or shallow) is case specific and typically the infield reinjection rate will vary with time as part of the steam field management strategy.

Reinjection in geothermal fields: A review of worldwide experience

Supercritical geothermal systems are very high-temperature geothermal systems that are located at depths near or below the brittle–ductile transition zone in the crust where the reservoir fluid is assumed to be in the supercritical state, that is for pure water, temperature and pressure are, respectively, in excess of 374 °C and 221 bar. These systems have garnered attention in recent years as a possible type of unconventional geothermal resource due to their very high enthalpy fluids. Supercritical conditions are often found at the roots of volcanic-hosted hydrothermal systems. More than 25 deep wells drilled in geothermal fields such as The Geysers, Salton Sea, and on Hawaii (USA), Kakkonda (Japan), Larderello (Italy), Krafla (Iceland), Los Humeros (Mexico), and Menengai (Kenya) have encountered temperatures in excess of 374 °C, and in some cases have encountered magma. Although fluid entries were documented for some of these wells, it remains an open question if permeability can be maintained at high enthalpy conditions. The IDDP-1 well at Krafla encountered magma, and ended up producing very high enthalpy fluids; however, these fluids were very corrosive and abrasive. Innovative drilling and well completion techniques are therefore needed to deal with the extreme temperatures and aggressive fluid chemistry compositions of these systems. New efforts are underway in Japan (northern Honshu), Italy (Larderello), Iceland (Reykjanes peninsula and Krafla), Mexico (Los Humeros), USA (Newberry), and New Zealand (Taupo Volcanic Zone) to investigate supercritical systems. Here, we review past studies, describe current research efforts, and outline the challenges and potential opportunities that these systems provide for international collaboration to ultimately utilize supercritical geothermal systems as a geothermal energy resource.

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Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities

Utilizing supercritical geothermal systems : a review of pas ventures and ongoing research activities

Chloride and Boron behavior in fluids of Los Humeros geothermal field (Mexico): A model based on the existence of deep acid brine

Reinjection in geothermal fields: An updated worldwide review 2020

Gas data of the Los Azufres geothermal field were analyzed using a method based on equilibrium of the Fischer-
Tropsch (FT) reaction: CH4 + 2H2O = 4H2 +CO2 and on the combined pyrite-hematite-magnetite (HSH2) reactions:
5/4 H2 +3/2 FeS2 +3/4 Fe2O3 + 7/4 H2O = 3 H2S +Fe3O4 in order to estimate reservoir temperature and
excess steam. The solution of equilibrium equations produces a grid (FT-HSH2). This method is suitable for
reservoirs with relatively high H2S but low H2 and NH3 concentrations in the fluid as is the case of the Los
Azufres well discharges. Reservoir temperature and reservoir excess steam values were estimated for initial and
present conditions in representative wells of the field to study the evolution of fluids, because of exploitation and
waste fluids reinjection. This method was very useful in estimating reservoir temperatures in vapor wells, while
in two-phase wells it was found that as the well produces a smaller fraction of water, the reservoir temperature
estimation agrees qualitatively with results from cationic or silica geothermometers. For liquid-dominated wells
the reservoir temperature estimations agree with temperatures obtained from the well simulator WELFLO. This indicates
that FT-HSH2 results provide the temperature of the fluid entering the well where the last equilibrium
occurs. Results show a decrease in reservoir temperatures in the southern zone of the field where intensive reinjection
takes place. With exploitation, it was also noted that the deep liquid phase in the reservoir is changing to
two-phase increasing the reservoir steam fraction and the non-condensable gases in well discharges.

/pdf/gas-geochemistry-for-the-los-azufres-michoacan-geothermal-rz2fm6pt4w.pdf

Gas geochemistry for the Los Azufres (Michoacán) geothermal reservoir, México

In this work, the response to exploitation of the Los Humeros geothermal reservoir was inferred through the study of the changes in production of wells, the thermodynamic conditions of reservoir fluids, and the chemical compositions of fluids over time. Up to 2012, almost 123 million tons of fluids had been extracted from the reservoir. Well bottom conditions (pressure and enthalpy) were calculated using heat and flow simulation. The changes in the composition of fluids seem to be related to boiling. In high-enthalpy wells, condensation in the well or in the reservoir was inferred to occur. Results also showed a decreasing trend in fluid salinity due to increasing boiling and condensation. The average reservoir liquid saturation for the field has a decreasing trend over time. Analysis of gas data suggested that the number of wells produce either a steam phase or condensed reinjection returns. According to the results, five main processes were identified: (a) pressure decrease and enthalpy increase that produces a moderate boiling process with steam gain; (b) iSignificant boiling and steam condensation; (c) production of returns from reinjection; (d) interaction with deep fluids, and (e) decrease in reservoir liquid saturation due to insufficient recharge.

The Response to Exploitation of the Los Humeros (México) Geothermal Reservoir

El basamento local del campo geotermico Los Humeros esta formado por un complejo metamorfico del Paleozoico y una secuencia sedimentaria, constituida por lutitas ricas en cloritas y muscovitas del Mesozoico, y una intrusion granitica del Terciario Inferior y andesitas del Plioceno. La presencia de dos yacimientos geotermicos fue reconocida con registros de presion realizados en el area del Colapso Central. Un yacimiento de vapor a profundidad y otro menos profundo que produce mezcla de fluidos (liquido + vapor), el cual esta claramente relacionado con la mineralogia hidrotermal. Los datos geoquimicos confirman la presencia de dos yacimientos. Uno somero con pH neutro y temperatura alrededor de 280 oC y otro mas profundo con temperatura mas alta. La clasificacion quimica de los fluidos muestra aguas tipo cloruradas y bicarbonatadas. Los estudios mineralogicos permitieron identificar ambas zonas productoras: Una con tipica alteracion hidrotermal considerada de alto rango, y otra donde pozos profundos localizados en la zona del Colapso Central tienen alta temperatura sin alteracion. La evidencia mineralogica confirma los limites de los dos yacimientos en el sistema. La dinamica del sistema se estudio a partir de los datos isotopicos de C, H y O del fluido de los pozos productores y de H y O de manantiales circunvecinos, con lo cual se postula un modelo preliminar.

/pdf/hydrodynamic-model-of-los-humeros-geothermal-field-mexico-1dfgl2zwua.pdf

Hydrodynamic model of Los Humeros geothermal field, Mexico,based on geochemical, mineralogical and isotopic data

The initial formation temperature field of the Los Humeros geothermal reservoir is presented. The stabilized formation temperatures were estimated for the 40 wells from this field using the Horner and the Spherical Radial Flow (SRF) methods. Both sets of formation temperatures were compared with the formation temperatures obtained by numerical simulation of the circulation and shut-in processes of the wells. From these comparisons, the formation temperatures obtained by the SRF method were chosen as more realistic than the Horner method temperatures. In the simulations, the last series of temperature logs was reproduced numerically considering circulation losses. Results for well H-26 are included as an example. Then isothermal curves of the formation temperatures for wells along different geological sections were obtained. Three sections are included, two longitudinal and one traverse, that illustrate the field initial temperature distribution. The observed temperature distribution shows the reservoir thermal features and the relationship of thermal anomalies and reservoir faults.

/pdf/initial-temperature-field-in-the-los-humeros-geothermal-3iuw5xw61x.pdf

Initial temperature field in the Los Humeros geothermal reservoir

Se presentan los modelos geoquimicos para los yacimientos geotermicos de Los Azufres y Los Humeros. En ambos casos lafase gaseosa tuvo un papel importante ya que de acuerdo con los fluidos producidos, el yacimiento de Los Azufres se clasificocomo de tipo vapor-liquido (VAP-LIQ) y Los Humeros se considera de tipo vapor dominante. El modelo conceptual del yacimientode Los Azufres se baso en la distribucion espacial de especies quimicas e isotopicas. Se estimo el “exceso de vapor de yacimiento”por medio del equilibrio de la reaccion de Fischer-Tropsch (CO2+4H2=CH4+2H2O), el cual se utilizo para corregir la composicionde los fluidos de descarga total para obtener la composicion de los fluidos del yacimiento. Los resultados indicaron que laconcentracion de especies volatiles es mayor a niveles someros, mientras que la concentracion de especies no volatiles es mayora profundidad. Este patron se interpreto como resultado de un proceso convectivo de ascenso y condensacion parcial de vapor enel yacimiento.En el campo de Los Humeros donde la fase liquida es escasa, se identificaron dos yacimientos. El mas profundo de tipovapor dominante con temperaturas entre 330 y 400°C y el mas somero de tipo liquido dominante con temperaturas menores. Elequilibrio gaseoso basado en la reaccion de Fischer-Tropsch (FT) y en el de la combinacion de reacciones pirita-hematita y piritamagnetita(HSH2) proporciono tanto la estimacion de temperatura de yacimiento como la de “exceso de vapor de yacimiento”.Considerando estos valores en una etapa temprana de explotacion y los mas recientes, se propone que los fluidos del yacimientoprofundo ascienden a traves de las fracturas hacia el yacimiento somero como consecuencia de la explotacion.

/pdf/gas-geochemistry-in-modeling-geothermal-reservoirs-58vhdouqzj.pdf

R. M. Barragán

Papers

Gas geochemistry for the Los Azufres (Michoacán) geothermal reservoir, México

The Response to Exploitation of the Los Humeros (México) Geothermal Reservoir

Hydrodynamic model of Los Humeros geothermal field, Mexico,based on geochemical, mineralogical and isotopic data

Initial temperature field in the Los Humeros geothermal reservoir

Gas geochemistry in modeling geothermal reservoirs