Mexican Geothermal Field Research Articles

Conceptual analysis of geothermal neighboring zones characterization with contrasting behavior: applied to a Mexican geothermal field

Conceptual analysis of geothermal neighboring zones characterization with contrasting behavior: applied to a Mexican geothermal field

Update and review of heat flow measurements in México

The main objective of this study is to report an update of the surface heat flow database of México. To our knowledge, this work is the first data compilation that integrates existing published and unpublished measurements to create a new heat flow map using a variety of data sources from 108 sites (transient borehole temperatures and temperature-depth profiles). Heat flow measurements in México are still relatively sparse. Updates of heat flow and geological data is required for a better understanding of the thermal regime of México, an accurate characterization of heat flow provinces, and to create a consistent geothermal map.The updated thermal database considers México’s continental and offshore zones. The new heat flow values are mainly located along the Baja California Peninsula and central México. From the new data, we defined the highest and the lowest heat flow values as 1263 mW/m2 and 4 mW/m2, respectively. This updated heat flow database helped us to identify regions with thermal anomalies that show values above average continental heat flow. More importantly, these high heat flow areas do not correspond to the known Mexican geothermal fields.

Optimal discretization time and mesh size in three-dimensional temperature field simulation in two Mexican geothermal fields

The sensitivity of neither the discretization time nor the mesh size is yet known in thermal modeling of geothermal systems. We determined their effect and optimal values in three-dimensional modeling of a magma chamber in two Mexican geothermal fields (Los Humeros, Puebla and La Primavera, Jalisco). Our results indicate that the discretization time is much more sensitive for the modeled subsurface temperatures than the mesh size. Therefore, all simulations must be carried out with the smallest discretization time (≤10 years for geothermal fields), which would result in the largest number of time steps. The importance of the mesh size is better understood in terms of the resolution of neighboring wells in a geothermal area. Four 3-D runs were simulated in the La Primavera geothermal field, whose results generally agreed with the actually measured temperatures in geothermal wells.

A Review of Geothermal Type-Curves with Damage Effect: A Case of Practical Apply to a Mexican Geothermal Field

A review of the art state was developed about the inflow relationships and their application for reservoir characterization. The theoretical development of the methodology for determining the damage effect using type-curves of the inflow relationships was shown. We show the process followed for achieve the geothermal type-curve affected with damage for reservoirs with mean salinities of 30000 ppm and temperatures up to 350℃. This type-curve was applied using measurement production data in a Mexican geothermal field. According with the obtained results is shown that the methodology for determining the damage effect using production measurements is a sure alternative for the damage effect calculation. It was used an alternative methodology in order to validate the damage presence and the obtained results were consistent. Last thing shows that both methodologies can be combined as a confident manner.

Land subsidence in the Cerro Prieto Geothermal Field, Baja California, Mexico, from 1994 to 2005: An integrated analysis of DInSAR, leveling and geological data

Cerro Prieto is the oldest and largest Mexican geothermal field in operation and has been producing electricity since 1973. The large amount of geothermal fluids extracted to supply steam to the power plants has resulted in considerable deformation in and around the field. The deformation includes land subsidence and related ground fissuring and faulting. These phenomena have produced severe damages to the local infrastructure such as roads, irrigation canals and other facilities. In this paper, the technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) is applied using C-band ENVISAR ASAR data acquired between 2003 and 2006 to determine the extent and amount of land subsidence in the Mexicali Valley near Cerro Prieto Geothermal Field. The DInSAR results were compared with published data from precise leveling surveys (1994–1997 and 1997–2006) and detailed geological information in order to improve understanding of the temporal and spatial distributions of anthropogenic subsidence in the Mexicali Valley. The leveling and DInSAR data were modeled to characterize the observed deformation in terms of fluid extraction. The results confirm that the tectonic faults control the spatial extent of the observed subsidence. These faults likely act as groundwater flow barriers for aquifers and reservoirs. The shape of the subsiding area coincides with the Cerro Prieto pull-apart basin. In addition, the changes in spatial pattern and rate of the subsidence are correlated with the development of the Cerro Prieto Geothermal Field.

A feedback-based inverse heat transfer method to estimate unperturbed temperatures in wellbores

This paper presents a feedback-based strategy to solve an inverse heat transfer problem for the estimation of unperturbed formation temperatures (UFT) from measured temperatures in wellbores. The feedback function uses the error between the measured and estimated temperatures during the shut-in process. Thus, an inverse heat transfer problem was solved in this way since the UFT represents the unknown initial conditions and the measured temperatures in the wellbore represents the particular solution of the PDE’S governing the heat transfer process in the formation and in the wellbore system. The performance of the method is illustrated via numerical simulations of two wells: (a) oil well FE-1227 from the Gulf of Mexico maritime zone and (b) well CP-0512 from Cerro Prieto Mexican geothermal field.

SolGeo: A new computer program for solute geothermometers and its application to Mexican geothermal fields

The freely available computer program Solute Geothermometers (SolGeo) was written and tested using geochemical data and reported geothermometric temperatures from several geothermal wells from around the world. Subsurface temperatures for the Mexican geothermal fields of Cerro Prieto, Las Tres Vírgenes, Los Azufres, and Los Humeros were estimated based on different solute geothermometers and found to be generally in close agreement with measured well temperatures when considering errors in the calculations and measurements. For Los Humeros wells it was concluded that a better agreement of chemical geothermometric temperatures is observed with static formation than with bottom-hole temperatures (BHTs). It was also found that the widely used Na–K geothermometric equations generally give more consistent and more reliable temperature estimates than the other geothermometers, which should therefore be applied with caution.

Numerical modeling of flow processes inside geothermal wells: An approach for predicting production characteristics with uncertainties

Abstract One dimensional steady and transient numerical modeling for describing the heat and fluid dynamic transport inside geothermal wells has been conducted. The mass, momentum and energy governing equations were solved using a segregated numerical scheme. Discretized governing equations for the fluid flow were coupled and solved with a fully implicit step by step method. The mathematical formulation used suitable empirical correlations for estimating the convective heat transfer coefficients as well as the shear stress and the void fraction parameters. Heat conduction across the wellbore materials was solved by an implicit central difference numerical scheme using the tri-diagonal matrix algorithm (TDMA). The flow characteristics of producer geothermal wells (pressure, temperature, enthalpy, heat fluxes, etc.) at each depth node were computed. Analytical data reported in the literature were used to validate the numerical capability of the wellbore simulator developed for this study (GEOWELLS). This simulator, together with another computer code (ORKISZEWSKI), was applied for modeling the heat and fluid flow processes inside some wells drilled in Mexican geothermal fields. The simulated pressure and temperature profiles were statistically compared against stable measured field data (through the computation of the residual sum of squares and Chi-square). A good agreement between the simulated and measured profiles of pressure and temperature was consistently obtained, having the best matching results for the GEOWELLS predictions. An analysis of the sensitivity and uncertainty was finally conducted to estimate the confidence to be accorded the simulation results predicted by GEOWELLS. Matching the sensitivity to variations in some input parameters (e.g., pressure, temperature, enthalpy and void fraction) was examined. The void fraction was identified as one of the most important parameters that affect the GEOWELLS simulations for matching measured field data correctly.

Thermal behaviour of geothermal wells using mud and air–water mixtures as drilling fluids

This paper describes a comparative study of the thermal behaviour of drilling fluids and the surrounding rock when air–water mixtures and conventional muds are used as drilling fluids in geothermal wells. The computations were performed with two numerical simulators: TEMLOPI/V.2, which is used to compute the transient temperature disturbance when mud is employed, and GEOMIST, which is used when air–water mixtures are employed as drilling fluid. Data from a well from the Las Tres Vı́rgenes Mexican geothermal field are used in this analysis. The results of simulation include temperatures computed during circulation and shut-in, and the latter results are compared with temperatures logged during drilling stoppages. It was found that the thermal disturbance caused by circulation of an air–water mixture has a smaller thermal effect than the thermal disturbance caused by drilling muds.

TEMLOPI/V.2: a computer program for estimation of fully transient temperatures in geothermal wells during circulation and shut-in

This paper describes the development, validation and application of the TEMLOPI/V.2 computer program. This program is a useful tool for estimating in-situ the transient temperature distribution of the fluids employed for drilling geothermal wells. TEMLOPI/V.2 is based on a mathematical model which is developed to consider two-dimensional transient heat transfer during drilling and shut-in conditions in and around a geothermal well. The solution of the partial differential equations is based on the finite-difference technique with an implicit scheme. This scheme serves to demonstrate the numerical solution procedure. Each radial grid node is placed in a different thermal region: flow inside the pipe, metal pipe wall, flow inside annulus, and the surrounding formation. The program was written in FORTRAN 77 using modular programming and runs on most IBM compatible personal computers. The software code, its architecture, input and output files, the solution algorithm, flow diagrams and source programs are described in detail. From validation tests, computed temperatures differ by less than 5°C from analytically obtained temperatures. Comparison of results from the fully transient TEMLOPI/V.2 simulator and the pseudo-transient version, TEMLOPI/V.1, with measured data shows that the fully transient model provides better results. Application of TEMLOPI/V.2 is demonstrated in a practical application study of well EAZ-2 from Los Azufres Mexican geothermal field.

TEMLOPI: a thermal simulator for estimation of drilling mud and formation temperatures during drilling of geothermal wells

This paper describes the development and application of the numerical code TEMLOPI v1.0, a useful tool for estimating the temperature distribution of the fluids employed for drilling geothermal wells. The simulator also allows estimation of the thermal disturbance of the surrounding rock caused by fluid circulation and well shut-in. TEMLOPI v1.0 is based on a mathematical model which considers the main heat transfer mechanisms and the heat exchange between the circulating fluid and the surrounding rock formation that occur during drilling of geothermal wells. The simulator was written in Fortran 77 using modular (block) programming. It runs on most IBM compatible personal computers and can be used in-situ. Input data includes the well geometry, the fluid and flow characteristics and the initial (undisturbed) formation temperature. Output files contain the transient temperature distribution (temperature vs depth) in the fluid flowing down the drill pipe and the annulus, the well inner face and the radial distribution in the surrounding rock. The software code model, architecture, input and output files and the solution algorithm are described in detail. Results obtained were validated by comparison with data published in the specialized literature and with data from well Az-29 from the Los Azufres Mexican geothermal field.

Developments in geothermal energy in Mexico—part twenty-eight: The role of petrophysical studies in the development of the Mexican geothermal resources

The host rocks of geothermal reservoirs perform important functions as structural elements and storage media for the hot reservoir fluids. They also provide the transport medium of the fluids. Characterizing the ability of geological formations to perform these functions is a fundamental requirement for both feasibility studies and the development and exploitation of geothermal resources. The heat content of the system, the fraction of recoverable heat, and the rate at which this fraction can be extracted are important factors in the technical and economic viability of a geothermal project. They depend greatly on the characteristics of the bearing rocks. Only a limited amount of appropriate rock property data is available. This restricts geothermal energy development. Laboratory measurements under simulated geothermal reservoir conditions in rock samples from drill cores have proved to be the most powerful tool to generate the necessary rock property information. Typical results of a number of petrophysical properties which have been determined using this technique on rocks from four Mexican geothermal fields are presented and discussed. These results illustrate the potential and importance of petrophysical research programmes as a tool to generate data and understand the properties and behaviour of reservoir rocks.

Radon mapping for locating geothermal energy sources

Geothermal energy sources are usually associated with volcanic regions where hot water springs and vapour emanation open up large areas of interest. The final evaluation of a possible worthwhile area for electric power production is carried out by drilling deep wells to measure in them well-known parameters to determine the potential of the well. Since drilling such wells is very expensive, it is necessary to reduce their number to a minimum by studying the area prior to drilling. Amongst the studies that contribute to useful information is radon mapping of the areas of interest. Interpretation of these results and other data provided be geophysical survey limit the number of boreholes required. This paper describes radon mapping by means of registering α-particles in thin-plastic Solid State Nuclear Track Detectors. Studies were made in four Mexican geothermal fields for the National Agency for Electric Power Supply (CFE).

Developments in geothermal energy in Mexico—part eleven: Two phase flow and the sizing of pipelines using the FLUDOF computer programme

Cost savings and thermodynamic advantages can result from the two phase conduction of geothermal fluid from well heads to central plant. A design methodology for two phase geothermal pipeline sizing is developed. A computer programme using the methodology is compared with field experiments in two Mexican geothermal fields, one situated in a plain and the other in a mountainous area. The calculations for the mountainous terrain pipeline agree within 10% with the experimental data. For the tests in flat terrain there are large errors attributed to severe scaling of pipelines. It is concluded that the programme FLUDOF requires improvement to allow for the effect of scaling in geothermal pipelines.

Developments in geothermal energy in Mexico—Part three: Economics of wellhead versus central power plants

A comparative economic analysis has been made between a single 110 MW e plant using concentrated steam from various wells, condensers and extractors for non-condensable gases to maximize its efficiency, and a system of 22 units, each with a capacity of 5 MW e, with the steam discharged at atmospheric pressure. The costs used for this comparison have been obtained from experience in Mexican geothermal fields at both Cerro Prieto and Los Azufres. It is concluded that the second alternative is very attractive and should be analyzed in detail for each project where both the production of steam and the generation of electricity are contemplated. The results of this analysis were presented at a Geothermal Conference and Workshop held at San Diego, California, U.S.A. in July 1985 sponsored by the Instituto de Investigaciones Electricas, Cuernavaca, Mexico and the Electric Power Research Institute, Palo Alto, California, U.S.A.

Developments in geothermal energy in Mexico—part eight: Geothermal reservoir energy recovery: A 3-D numerical simulation study of the Cerro Prieto geothermal field

Cerro Prieto is the most developed Mexican geothermal field. Currently, two power plants produce electricity from it. The oldest, CP I, as been on line for more than a decade; CP II recently started producing at half capacity, and CP III is scheduled to come on line soon. In this work we investigate the mass and heat reserves, the corresponding deliverability, and the expected quality of the heat delivered, in relation to CP I. We also inquire into the likely effect of the planned production of the CP II and CP III power plants on the future performance of CP I. The investigation is accomplished via numerical simulation. Our results indicate that the reserves of mass and heat in the layers that feed CP I are adequate for a thirty year economic life of the plant, that the quality of the produced heat will decline with time to about 85% of its peak value, and that the main effect of production by CP II and CP III is to enhance recharge by cool water of the zone that feeds CP I.

Chemical studies in Mexican geothermal fields

During the period from the beginning of 1968 to August 1969, chemical samples have been analysed from the fields of Los Humeros (Pue.), Ixtlán de los Hervores (Mich.), Los Negritos (Mich.), Pathé (Hid.) and Cerro Prieto (B. Cal.). Quantitative analyses for up to sixteen principal elements or compounds have been made on water samples from these zones, as well as from selected hot springs in adjoining areas, and steam and gas discharges have been analysed for seven gaseous elements and compounds. In Los Humeros, where the manifestations consist only of dry steam vents, water analyses have been made on condensate, but in the other areas the analyses have been made on samples from hot springs, geysers and mud pools. In Ixtlán de los Hervores, water samples were also available from two test drillholes. Samples have been taken from a large enough number of points to permit iso-chemical contours of several kinds to be drawn in each area, and is found that the resulting patterns show a striking correlation with certain of the geological and geophysical data obtained in the course of the investigation programme. These correlations have been of considerable value for siting prospecting drillholes in the Ixtlán area. A number of the more important chemical relationships have been plotted in the conventional type of triangle or other form of diagram and compared with similar data from fields in other parts of the world.