The effect of salinity and gas saturation of a geothermal fluid on the reservoir permeability reduction

Highly saline geothermal reservoirs show problems of salt precipitation on the rock formation reducing its permeability and the well’s productivity. In this study, theoretical curves of mass productivity of geothermal wells (inflow type curves) were obtained considering ternary mixtures of H2O-CO2-NaCl of up to 25% salinity in weight and under different initial conditions of gas saturation of the fluid. The sensitivity analysis to the initial concentration of salts and initial gas saturation was carried out using the simulator TOUGH2. The developed type curves are focused to reservoirs with criti-cal characteristics such as, low permeability, ranges of high salt precipitation and high gas saturation. The obtained curves show three clearly defined zones as a function of the degree of exploitation of the well: no salt precipitation zones; transition zones; and salt precipitation zones. It was found that salt precipitation in the reservoir occurs in greater intensity at higher initial concentrations of dissolved salts and higher gas saturation. In some cases, scale obstructs the pores of the rock formation drastically reducing its permeability. It is proposed that type curves could be used as complementary tools for the analysis of wells and for the selection of pertinent strategies for the exploitation of geothermal fields.

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Enhanced Geothermal Systems Projects and its Potential for Carbon Storage

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.732-733.109 ◽

2013 ◽

Vol 732-733 ◽

pp. 109-115 ◽

Cited By ~ 1

Author(s):

Chao Yin Feng

Keyword(s):

Carbon Dioxide ◽

Power Plants ◽

Subsurface Water ◽

Working Fluid ◽

Low Permeability ◽

Enhanced Geothermal Systems ◽

Geothermal Systems ◽

Geothermal Fields ◽

Geological Conditions ◽

Geothermal Wells

Enhanced Geothermal Systems represent a series of technology, which use engineering methods to improve the performance of geothermal power plant. In some geothermal fields, the rocks are in high temperature but a low permeability, or the subsurface water is scarce. In these geological conditions, cool water was injected into the geothermal wells to fracture the tight rock and create man-made reservoir for thermal exploitation. Furthermore, these engineering methods can be utilized to improve the productivity of pre-existing hydrothermal power plants. To save water and treat the global warming, using carbon dioxide instead of water as working fluid was proposed. Numerical simulation reveals that the carbon dioxide has numerous advantages over water as working fluid in the heat mining process. The precipitation caused by carbon dioxide will restore part of carbon dioxide in the rock and reduce the micro-seismicity risk.

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Welltest analysis of hydraulically fractured tight gas reservoirs: a field example from Perth Basin, Western Australia

The APPEA Journal ◽

10.1071/aj11047 ◽

2012 ◽

Vol 52 (1) ◽

pp. 587 ◽

Cited By ~ 1

Author(s):

Hassan Bahrami ◽

Vineeth Jayan ◽

Reza Rezaee ◽

Dr Mofazzal Hossain

Keyword(s):

Radial Flow ◽

Second Derivative ◽

Tight Gas ◽

Transient Pressure ◽

Gas Reservoirs ◽

Type Curves ◽

Tight Gas Reservoirs ◽

Diagnostic Plots ◽

Reservoir Permeability ◽

Reservoir Flow

Welltest interpretation requires the diagnosis of reservoir flow regimes to determine basic reservoir characteristics. In hydraulically fractured tight gas reservoirs, the reservoir flow regimes may not clearly be revealed on diagnostic plots of transient pressure and its derivative due to extensive wellbore storage effect, fracture characteristics, heterogeneity, and complexity of reservoir. Thus, the use of conventional welltest analysis in interpreting the limited acquired data may fail to provide reliable results, causing erroneous outcomes. To overcome such issues, the second derivative of transient pressure may help eliminate a number of uncertainties associated with welltest analysis and provide a better estimate of the reservoir dynamic parameters. This paper describes a new approach regarding welltest interpretation for hydraulically fractured tight gas reservoirs—using the second derivative of transient pressure. Reservoir simulations are run for several cases of non-fractured and hydraulically fractured wells to generate different type curves of pressure second derivative, and for use in welltest analysis. A field example from a Western Australian hydraulically fractured tight gas welltest analysis is shown, in which the radial flow regime could not be identified using standard pressure build-up diagnostic plots; therefore, it was not possible to have a reliable estimate of reservoir permeability. The proposed second derivative of pressure approach was used to predict the radial flow regime trend based on the generated type curves by reservoir simulation, to estimate the reservoir permeability and skin factor. Using this analysis approach, the permeability derived from the welltest was in good agreement with the average core permeability in the well, thus confirming the methodology’s reliability.

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Experimentally Accessible Orbits Near a Bykov Cycle

International Journal of Bifurcation and Chaos ◽

10.1142/s021812742030030x ◽

2020 ◽

Vol 30 (10) ◽

pp. 2030030

Author(s):

Roberto Barrio ◽

Maria Carvalho ◽

Luísa Castro ◽

Alexandre A. P. Rodrigues

Keyword(s):

Chaotic Dynamics ◽

Vector Fields ◽

Initial Conditions ◽

Parabolic Type ◽

Chaotic Attractors ◽

Heteroclinic Cycle ◽

Type Curves ◽

Local And Global Bifurcations ◽

Domain Of Parameters ◽

Two Parameter

This paper reports numerical experiments done on a two-parameter family of vector fields which unfold an attracting heteroclinic cycle linking two saddle-foci. We investigated both local and global bifurcations due to symmetry breaking in order to detect either hyperbolic or chaotic dynamics. Although a complete understanding of the corresponding bifurcation diagram and the mechanisms underlying the dynamical changes is still out of reach, using a combination of theoretical tools and computer simulations we have uncovered some complex patterns. We have selected suitable initial conditions to analyze the bifurcation diagrams, and regarding these solutions we have located: (a) an open domain of parameters with regular dynamics; (b) infinitely many parabolic-type curves associated to homoclinic Shilnikov cycles which act as organizing centers; (c) a crisis region related to the destruction or creation of chaotic attractors; (d) a large Lebesgue measure set of parameters where chaotic regimes are dominant, though sinks and chaotic attractors may coexist, and in whose complement we observe shrimps.

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The tasks of hydraulics of steam-water wells in the development of steam-hydrothermal fields

E3S Web of Conferences ◽

10.1051/e3sconf/20185601009 ◽

2018 ◽

Vol 56 ◽

pp. 01009

Author(s):

Alla Chermoshentseva ◽

Alexander Shulyupin

Keyword(s):

Mathematical Models ◽

Flow Conditions ◽

Geothermal Fields ◽

Water Wells ◽

Geothermal Wells ◽

Practical Development ◽

Hydrothermal Fields

Actual problems and prospects of practical development of geothermal fields are noted in the present work. The mathematical models for the calculation of flows in steam-water geothermal wells are described. The author's models cover the whole range of possible flow conditions.

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Simple interpretations of chemical transients in multi-feed, two-phase geothermal wells: examples from philippine geothermal fields

Geothermics ◽

10.1016/0375-6505(91)90011-j ◽

1991 ◽

Vol 20 (3) ◽

pp. 135-145 ◽

Cited By ~ 1

Author(s):

J.R. Ruaya ◽

R.P. Solis ◽

R.R. Solaña ◽

J.S. Seastres

Keyword(s):

Two Phase ◽

Geothermal Fields ◽

Geothermal Wells

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Solution and type curves for the seepage model of the water-bearing coalbed with leakage recharge

Earth Sciences Research Journal ◽

10.15446/esrj.v21n1.63003 ◽

2017 ◽

Vol 21 (1) ◽

pp. 17 ◽

Cited By ~ 1

Author(s):

Wangang Chen ◽

Yu Yang ◽

Hansen Sun ◽

Chengwei Zhang ◽

Qin Wen ◽

...

Keyword(s):

Coalbed Methane ◽

Radial Flow ◽

Curve Matching ◽

Pressure Derivative ◽

Type Curve ◽

Type Curves ◽

Reservoir Permeability ◽

Leakage Coefficient ◽

Seepage Theory ◽

Seepage Model

To analyze the effects of the leakage recharge of the aquifer on the initial dewatering of coalbed methane wells, the mathematical seepage model of water in the coalbed considering the aquifer leakage was established by using the leakage coefficient according to the unsteady seepage theory. The model was solved after Laplace transform and the Stehfest numerical reverse inversion was used to obtain the solution in right space. Then, the log-log type curves of pressure and pressure derivative were created with new combinations of parameters. Based on the natural seepage mechanism, the influence of aquifer leakage on curve shape was judged. It is found that the radial flow ends earlier as the leakage coefficient increases. Moreover, it was proposed to obtain reservoir permeability, skin factor, and leakage coefficient by using type curve matching. The type curves are useful for quantitatively evaluating the level of leakage, thereby guiding the adjustment of the following production system for CBM wells. Curvas de solución y tipo para el modelo de filtración de capas carboníferas acuíferas con recarga de fugasResumenEste estudio estableció el modelo matemático de filtración de agua en una capa carbonífera al estimar la salida acuífera con el uso del coeficiente de fuga, de acuerdo con la teoría de filtración inestable, para analizar los efectos en la recarga de pérdida de fluidos de un acuífero en el drenado inicial para pozos de gas metano. El modelo se resolvió tras usar la transformación Laplace y la inversión numérica Stehfest para encontrar la respuesta en el lugar indicado. Luego, se creó la representación algorítmica de la presión y la presión derivativa con nuevas combinaciones de parámetros. Se evaluó la influencia de la pérdida de fluido del acuífero en la forma de la curva con base al mecanismo físico de filtración. Se estableció que el flujo radial finaliza antes de que el coeficiente de pérdida de fluido se incremente. Además, se propone el uso de la curva tipo correspondiente para obtener la permeabilidad del reservorio, el factor de daño y el coeficiente de pérdida de fluido. Las curvas tipo son útiles para evaluar cuantitativamente el nivel de la pérdida de fluido, y de esta manera guiar el ajuste de un sistema de producción consecuente para pozos de gas metano de carbón.

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A new method of damage determination in geothermal wells from geothermal inflow with application to Los Humeros, Mexico

Geofísica Internacional ◽

10.22201/igeof.00167169p.2008.47.4.2148 ◽

2008 ◽

Vol 47 (4) ◽

pp. 371-382

Author(s):

A. Aragón ◽

S. L. Moya ◽

A. García Gutiérrez ◽

V. Arellano

Keyword(s):

Reservoir Characterization ◽

Geothermal Field ◽

Damage Effect ◽

Transient Pressure ◽

Type Curves ◽

Pressure Tests ◽

Geothermal Wells ◽

Productivity Indices ◽

Well Damage ◽

Inflow Performance

Geothermal inflow type curves were obtained for different values of well damage (i.e., inflow performance relationships). The method was evaluated by diagnosing the damage of thirteen producing wells in the Los Hu- meros, Puebla, Me?xico geothermal field. Permeability determinations were carried out for these wells and their productivity indices were estimated. Comparison of the diagnoses made via damage effects against the results of field pressure tests showed that the maximum difference between both approaches is on the order of 0.7 damage units. The methodology allows reservoir characterization along its productive life, since several production tests are carried out while the reservoir is producing. The data obtained from production tests are used to determine the damage effect and permeability of the rock formation. Previously the damage (skin factor) could only be determined from the analyses of transient pressure tests.

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Formation permeability at the feedzone of geothermal wells em- ploying inflow type-curves

Geofísica Internacional ◽

10.22201/igeof.00167169p.2001.40.3.320 ◽

2001 ◽

Vol 40 (3) ◽

pp. 163-180

Author(s):

Sara L. Moya ◽

Daniel Uribe ◽

Alfonso Aragón ◽

Alfonso García

Keyword(s):

Type Curves ◽

Geothermal Wells ◽

Inflow Performance

En este trabajo se hace un análisis preliminar de la aplicabilidad de las curvas GIPR (Geothermal Inflow Performance Relationships), para la estimación de permeabilidades de formaciones geotérmicas en las zonas de alimentación de los pozos. Las curvas GIPR (denominadas también curvas-tipo) son curvas características teóricas que relacionan velocidad de flujo másico producido y presión fluyente en la zona de alimentación del pozo. La metodología consiste en traslapar la curva de influjo del pozo (curva característica del pozo) con diferentes curvas tipo y el valor de permeabilidad implícito en la curva tipo del mejor traslape es el valor de permeabilidad buscado. Es importante destacar que esta metodología no requiere medir en campo la curva de influjo del pozo. El empleo de dos curvas de referencia adimensionales del comportamiento de influjo geotérmico previamente obtenidas, una para productividad másica y otra para productividad térmica, permiten el cálculo de la curva de influjo completa del pozo, desde una sola medición flujo másico-presión-entalpía específica (W-P-h) a boca o fondo de pozo, y conociendo la presión del yacimiento en la zona de alimentación del mismo (Ps). Para evaluar la aplicabilidad de la metodología propuesta se consideraron datos (W,P,h) a boca de pozo correspondientes a pruebas de descarga previas de seis pozos del campo geotérmico de Los Azufres. Las permeabilidades inferidas aplicando la metodología están en el rango establecido para este campo. Las curvas de influjo calculadas para los pozos fueron validadas comparando sus respectivas curvas de salida estimadas con los datos completos de las pruebas de descarga correspondientes. Las desviaciones encontradas son del orden del 6% para presión de cabezal y del 2% para entalpía específica, cuando la incertidumbre de los datos de campo es baja. La metodología que se propone en este trabajo puede considerarse como una herramienta complementaria a las mediciones de laboratorio en núcleos de perforación y a las pruebas de presión transitorias efectuadas en campo. Las curvas tipo de influjo incluyen los efectos de las condiciones iniciales del yacimiento, de las propiedades de la formación y el fluido y de la producción másica acumulada del pozo, para pozos con alimentación de flujo bifásico. El factor de daño en los pozos no fue considerado.

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