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Journal of Asian Earth Sciences 45 (2012) 256–267

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Journal of Asian Earth Sciences

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Exploration and assessment of the geothermal resources in the Hammam Faraunhot spring, Sinai Peninsula, Egypt

Mohamed Abdel Zaher a,⇑, Hakim Saibi b, Jun Nishijima c, Yasuhiro Fujimitsu c, Hany Mesbah a,Sachio Ehara c

a National Research Institute of Astronomy and Geophysics, Helwan, Cairo 11421, Egyptb Laboratory of Exploration Geophysics, Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japanc Laboratory of Geothermics, Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan

a r t i c l e i n f o

Article history:Received 5 November 2010Received in revised form 17 October 2011Accepted 10 November 2011Available online 3 December 2011

Keywords:Geothermal resourcesGravity surveyMagnetotelluric surveyGulf of SuezHammam FaraunHot spring

1367-9120/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.jseaes.2011.11.007

⇑ Corresponding author. Tel.: +20 2 25560645; fax:E-mail address: [email protected] (M. Abdel

a b s t r a c t

The tectonic position of Egypt in the northeastern corner of the African continent suggests that it maypossess significant geothermal resources, especially along its eastern margin. The most promising areasfor geothermal development in the northwest Red Sea-Gulf of Suez rift system are located where theeastern shore of the Gulf of Suez is characterized by superficial thermal manifestations, including a clus-ter of hot springs with varied temperatures. Magnetotelluric and gravity-reconnaissance surveys werecarried out over the geothermal region of Hammam Faraun to determine the subsurface electric resistiv-ity and the densities that are related to rock units. These surveys were conducted along profiles. One-dimensional (1D) and two-dimensional (2D) inversion model techniques were applied on the MT data,integrating the 2D inversion of gravity data. The objectives of these surveys were to determine andparameterize the subsurface source of the Hammam Faraun hot spring and to determine the origin of thisspring. Based on this data, a conceptual model and numerical simulation were made of the geothermalarea of Hammam Faraun. The numerical simulation succeeded in determining the characteristics ofthe heat sources beneath the Hammam Faraun hot spring and showed that the hot spring originates froma high heat flow and deep ground water circulation in the subsurface reservoir that are controlled byfaults. These studies were followed by an assessment of the geothermal potential for electric generationfrom the Hammam Faraun hot spring. The value of the estimated potential is 28.34 MW, as the reservoiris assumed to be only 500 m thick. This value would be enough for the desalination of water for bothhuman and agricultural consumption.

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1. Introduction

Egypt, in the northeastern corner of the African plate, is boundto the east by what has been interpreted as a median spreadingcenter in the Red Sea and Gulf of Suez (Mckenzie et al., 1970).Therefore, this area is an important candidate for geothermaldevelopment. Additionally, the most promising areas for geother-mal development in the northwestern Red Sea-Gulf of Suez rift sys-tem are located where the eastern shore of the Gulf of Suez ischaracterized by superficial thermal manifestations, including acluster of hot springs with various temperatures. The previouslyobtained data indicate that a temperature of 120 �C or higher existsin the reservoir located adjacent to the Gulf of Suez and the Red Seacoastal zone (Morgan et al., 1983). The most important area forgeothermal manifestation is located in the Hammam Faraun hot

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+20 2 25548020.Zaher).

spring (see Fig. 1), which is the hottest spring in Egypt (Morganet al., 1983).

In this study, MT and gravity-reconnaissance surveys werecarried out over the geothermal region of Hammam Faraun todetermine the subsurface densities and electric resistivity relatedto rock units. These surveys were conducted along two profiles(shown in Fig. 1). One-dimensional (1D) and two-dimensional(2D) inversion model techniques were applied to the MT data, inte-grating the 2D inversion of the gravity data. The resistivity methodprovides information about rock properties and the subsurfacestructure. This information can be used to determine the geometryof a hydrothermal reservoir, its depth and the location of the heatsource. To complement the resistivity method of choice (MT), grav-ity surveys were conducted along the MT survey lines to interpretthe subsurface and to aid in locating the prospective heat source,and thereby to elicit the origin of the Hammam Faraun hot spring.

Integrating the MT and gravity data reduces the ambiguity ofeither dataset, produces a more robust interpretation and providesa comprehensive picture of the geothermal system’s characteristics,

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Fig. 1. Topography of the Gulf of Suez region from the GTOPO30 dataset (Gesch et al., 1999). This figure shows the location of the hot springs on the eastern and westernmargins of the Gulf. Locations of the measured gravity and MT sites are plotted on a topographic map of the study area.

M. Abdel Zaher et al. / Journal of Asian Earth Sciences 45 (2012) 256–267 257

helping to create an assessment of the geothermal potential forelectric generation from the Hammam Faraun hot spring.

Previous studies have been conducted on the geological andgeophysical explorations for geothermal investigations (Demirelet al., 2004; Heise et al., 2007; Mogi and Nakama, 1993; Saibiet al., 2006, 2008). MT surveys were carried out on the southernmargin of the Mount Amiata geothermal region (Tuscany, Italy)by Volpi et al. (2003), with the aim of defining the shallow anddeep electric structures related to the local geothermal reservoirsand system heat recharge. Schill et al. (2010) carried out a 2D mag-netotelluric and 3D inversion of existing gravity data based on a 3Dgeological model in the area of the geothermal power plant ofSoultzsous–Forêts in northeastern France. Naganjaneyulu andSantosh (2011) analyzed MT data along the N–S trendingKalugumalai–Tiruchengode profile in the Madurai Block in south-ern India to evaluate the crustal architecture and its implicationson the tectonic development of Madurai Block. Sari and Salk(2006) estimated the thickness of the sedimentary cover on the

Menderes Massif in western Turkey as deduced from 2D and 3Danalyses of the gravity data. Abdel Zaher et al. (2011) evaluatedpotential geothermal resources in the Gulf of Suez region usingboth bottom-hole temperature data and geophysical data.

2. Geological and geochemical background

The Gulf of Suez is a failed intercontinental rift that forms theNW–SE continuation of the Red Sea rift system. This rift is mainlycontrolled structurally by extensional normal faults that strikenorthwest and form a complex array of tilted half-grabens andasymmetric horsts (Pivnik et al., 2003). The Hammam Faraun tiltedblock is one of the main fault blocks in the central dip province ofthe Suez rift, and it is bound on the east and west by major normalfault zones (Fig. 1). These major border fault zones are in excess of25 km long, dip steeply to the west and have displacementsbetween 2 and 5 km long (Moustafa and Abdeen, 1992; Sharp

Fig. 2. (a) Simplified geological map of the study area that shows that the Hammam Faraun region represents a faulted tilted block that has a half-graben geometry dippingmoderately to the east (after Moustafa and Abdeen, 1992; Sharp et al., 2000). (b) The simplified stratigraphy of the Hammam Faraun region, located in the eastern margin ofthe Gulf of Suez (modified from Jackson et al., 2002).

258 M. Abdel Zaher et al. / Journal of Asian Earth Sciences 45 (2012) 256–267

et al., 2000). The geological map of the Hammam Faraun fault block(Fig. 2) shows that this fault block has a half-graben geometry dip-ping moderately to the east that is up to 25 km wide and 40 kmlong. The shallow geological succession in the Hammam Faraunarea is distinguished by sand, conglomerates, sandy limestone, la-goonal gypsum limestone, salty limestone and chalk with flintylimestone. This succession varies with age from the post-Pliocene,Pliocene, Miocene, Oligocene, Eocene and upper Cretaceous eras,respectively (Jackson et al., 2002) (Fig. 2). The Hammam Faraunhot spring (with a temperature of 70 �C) issues from faulted dolo-mitic Eocene limestone.

Several studies have been carried out to investigate the seismicactivity in the Gulf of Suez (Dahy, 2010; LePichon and Francheteau,1978; Mckenzie et al., 1970; Piersanti et al., 2001). These studiessuggest that the seismic activity in the Gulf of Suez is scatteredand does not have any distinct trend. Dahy (2010) studied the re-cent shallow earthquake occurrences in the Gulf of Suez region anddivided it into two zones; the first one, which extends from themouth of the Gulf of Suez to the center is a seismically active zoneand is characterized by the occurrences of shallow, micro, small,moderate and large earthquakes. The second area lies betweenthe central area of the Gulf of Suez and the end of it and is charac-terized by less-frequent earthquakes of different magnituderanges.

Chemical and isotopic analyses of thermal water from theHammam Faraun hot spring were conducted by Sturchio andArehart (1996). The most abundant solutes in the Hammam Faraunwater are Na and Cl, while Mg, Ca and SO4 are also prominent. ThepH values are near neutral, which indicates that the derivation ofsolutes is mainly from regional marine sedimentary rocks and

windblown deposits (marine aerosol and evaporate dust). Addi-tionally, the ratio of 3He/4He was recorded to be 0.256 times theatmospheric ratio (Ratm) in the gases emitted from the HammamFaraun hot spring, whereas this ratio equals eight times the Ratm

in the mantle. Hence, this ratio indicates that there is an excessof He (3.2%) in the Hammam Faraun hot spring that may beattributed to a deeper source of mantle (Sano et al., 1988). Sturchioand Arehart (1996) related the mantle He to the alteration in thesubsurface due to late Tertiary Period volcanic eruptions.

3. Field surveys

MT and gravity surveys were conducted in the study area(Fig. 1). MT data were measured from 16 stations along twoprofiles; one profile was parallel to the Gulf of Suez coast, andthe other profile was oriented northeast–southwest and as closeas possible to the line perpendicular to the coast of the Gulf ofSuez. The MT survey was performed using a Stratagem instrumentwith two frequency ranges: high (10 Hz to 100 kHz) and low(0.1 Hz to 1 kHz). The distance between the MT stations rangedfrom 500 m to 1000 m, depending on the available space forconstructing the instrument. The Stratagem represents a uniqueMT system that uses both natural and manmade electromagneticsignals to obtain a continuous electric sounding of the earthbeneath the measurement site. Electrode stakes are used to mea-sure electric fields and highly sensitive magnetic coils are used tomeasure magnetic fields. Low-frequency natural MT waves wererecorded using AMT only, and the measurement was then repeatedusing an artificial signal source for CSAMT. Additionally, a Scintrex


Autogravimeter CG-3 was used for the gravity survey; this is amicroprocessor-based automated gravity meter that has a mea-surement range of over 7000 mGals without resetting and a read-ing resolution of 0.005 mGals. To determine the distribution of thegravity anomalies in the Hammam Faraun area and assess the sub-terranean structure below the hot spring, an interval of 250 m wasselected between each station. All gravity stations were set atpoints where elevations were available from a topographic mapof the area being studied. Repeated readings at a base stationthroughout the field day determined meter drift.

4. Magnetotelluric method

4.1. One-dimensional inversion of MT data

A 1D inversion on an average fitting curve between the TE andTM modes of MT data was conducted using the Bostick and Occamalgorithms (Bostick, 1977; Constable et al., 1987). The Bostick andOccam transformations of the MT data are shown in Figs. 3 and 4;the lined blocks represent the Bostick transformation, and the boldblocks represent the Occam transformation. The Bostick transfor-mation represents one of the simplest ways to invert the MT dataand generates a continuous resistivity distribution plotted againstdepth (Bostick, 1977). However, the Occam inversion minimizesthe combination of the roughness and data fitting that leads to asimple model containing the essential properties of all possiblemodels fitting the MT data (Constable et al., 1987). We usedD + smoothing techniques to smooth the resistivity and phasecurves instead of other numerical smoothing techniques; this tech-nique specifically relates the apparent resistivity and phase of thesame component through a D + function (Beamish and Travassos,1992). In essence, this method finds the 1D earth that best fits bothparameters. Generally, the better the fit between the measured andpredicted data, the higher the quality of the inversion.

Moderately high resistive layers were recognized at shallowdepths, which can be interpreted as the presence of a highly resis-tive rock type. Jackson et al. (2002) demonstrated that a carbonate-dominated Eocene succession (the Thebes, Darat, Khababa andTanka formations) was detected in the Hammam Faraun region(Figs. 3 and 4). These resistive layers, followed by a moderatelyhigh conductive layer, may indicate the ground water reservoirin that area. Soundings 07 and 08 in Profile 1 (Fig. 3) were con-ducted where the Hammam Faraun hot spring is located, and theyshow the existence of a highly resistive body (>1000 Ohm m) at adepth near 1000 m. In addition, the Sounding 16 at Profile 2(Fig. 4) showed the same phenomena below the Hammam Faraunhot spring. This body had higher resistivity than the surroundingareas and extended downward, which may reflect the basementrock.

4.2. Two-dimensional inversion of MT data

The MT data were also inverted with a 2D smooth-model inver-sion routine using the method of nonlinear conjugate gradients(NLCGs). The forward-model simulations were computed using fi-nite difference equations that were generated by network analogsto Maxwell’s equations. Coarse mesh generation was used wherethe thickness of the rows increases with depth according to a fixed,pre-assigned scheme. The resistivity of the initial model was set at100 Ohm m. The NLCG algorithm attempts to minimize an objec-tive function that is the sum of the normalized data misfits andthe smoothness of the model (Rodi and Mackie, 2001). The tradeoffbetween fitting the MT data and adhering to the model’s constraintis controlled by the regularization parameter TAU, which does notautomatically reach a target misfit. Rather, the 2D model was

obtained after several inversions using different values of TAU thatgave the smallest root mean square (RMS) error and the smoothestmodel. Fig. 5 shows the integration between 2D inversion modelsalong Profiles 1 and 2 that gave reasonable results for the subsur-face structure of the area being studied.

The inversion of the MT data showed the existence of a highlyresistive body at a shallow depth below the Hammam Faraun hotspring that demonstrates that the Hammam Faraun hot springoriginates from the uplifting of the hot plutonic basement rock.Kirsch (2009) demonstrates a resistivity for a sand-saturated layerranging between 40 and 200 Ohm m. Thus, the subsurface ground-water aquifer can be recognized and delineated with resistivitiesranging from 60 to 200 Ohm m above the high resistive region(>1000 Ohm m). The reservoir also extends deeper northwardand eastward of the hot spring. This area is also characterized byhighly conductive layers at the shallower part of the profiles thatare related to the mudstone- and siltstone-dominated Nukhul For-mation (Jackson et al., 2002).

5. Two-dimensional forward model of the gravity data

Before gravity measurements can be used to assess geology, thenumerous and occasionally large effects of masses that are not ofdirect geological interest must be eliminated. Standard protocolsfor gravity measurements were followed (see Battaglia et al.,2008 for a summary). Two opposing effects are involved: a de-crease in gravity due to an increased distance from the observationpoint to the Earth’s center of mass (the free-air correction) and anincrease due to the gravitational pull of the rock material betweenthe observation point and the sea level (the Bouguer correction). Inapplying the free-air correction, the observed gravity values weremathematically converted to values corrected for differences inelevation, thus further isolating the geological component of thegravitational field.

The gravity model can be defined by finding geometrical anddensity parameters where the difference between the measuredand calculated gravity is minimized and the a priori informationabout the geological structure is respected. There are many appro-priate algorithms for 2D models of gravity data. The majority of thealgorithms assume that the density above the basement interfaceis uniform. A constant density is adopted in modeling schemes(Bhattacharyya and Navolio, 1975). The change in the boundaryof the mass contrast and differential density values at variousdepths should be taken into consideration in modeling procedures(Chakravarti et al., 2001).

2D forward-gravity models (Figs. 6 and 7) were constructedalong NW–SE and NE–SW profiles (shown in Fig. 1), using the 2Dpolygon method for an arbitrarily shaped body (Talwani et al.,1959), where each layer was assumed to be a one-polygon algo-rithm with an assumed depth-dependent density contrast betweenthe basement rock and the sedimentary cover. These models wereconducted based on geological and MT intuition.

For the computation of 2D gravity models, the subsurface stratawere assumed to be three layers with different density properties:surface deposits, sedimentary section and basement rock (mainlygranites). The density of different lithologies in the sedimentarysection was taken as an average (2.4 g/cm3), and the density forthe basement layer was 2.67 g/cm3. The density of the surface layerwas previously calculated to be 1.950 g/cm3.

6. Conceptual hydrothermal model

Temperature measurements made by Morgan et al. (1985) inthe area of study show that the emergence temperature (the watertemperature of the hot spring at the surface) in the Hammam

Fig. 3. One-dimensional inversion of the MT data at all sites on Profile 1. The striped block represents the Bostick inversion, and the solid line represents the Occam smoothinversion.


Fig. 4. One-dimensional inversion of the MT data at all sites on Profile 2. The striped block represents the Bostick inversion, and the solid line represents the Ocean smoothinversion.


Fig. 5. Two-dimensional inversion resistivity model along Profiles 1 and 2, using the method of nonlinear conjugate gradients. The origin of the Hammam Faraun hot spring isdue to the uplift of highly resistive basement rock.

Fig. 6. Two-dimensional conceptual structural model based on the forward modeling of the gravity data for the Hammam Faraun area along the line A–B (parallel to the coastof the Gulf of Suez).


Faraun area is 70 �C and increases with depth by 48 �C/km. Themeasured temperature gradient is moderately high and indicatesthat this area is interesting for geothermal studies. A conceptualmodel of the hydrothermal system in the Hammam Faraun hotspring was proposed based on information extracted from the geo-logical and geochemical backgrounds and geophysical data. Thisinformation suggested that the source of the hot spring is the tec-tonic uplift of hotter rocks causing deep-fluid circulation throughfaults on the surface of the basement rock (Fig. 8). Such faults allowthe formation of discharging conduits for water ascending from adepth after being heated and mixed with other water types;namely, the uplifted basement is the site of high heat flow. This up-lift exists at a shallow depth and has limited extension. After heat-ing, these mixed waters rise through a vertical fracture that is

assumed to come from the intersection of two faults that are par-allel and moderately perpendicular to the Gulf of Suez margin.

7. Hydrothermal numerical simulation

The purpose of mathematical modeling is to develop a com-puter model that reflects essential features of the considered phe-nomenon or that represents a real system. A 3D finite differencemodel (HYDROTHERM, Version 2.2; Hayba and Ingebritsen, 1994)was used to simulate groundwater flow and heat transport in theporous medium below the hot spring.

A 3D discretization of the Hammam Faraun region is shown inFig. 9. The model of Hammam Faraun covers 77 km2 and was

Fig. 7. Two-dimensional conceptual structural model based on the forward modeling of the gravity data for the Hammam Faraun area along the line C–D (moderatelyperpendicular to the Gulf of Suez margin).

Fig. 8. Schematic diagrams showing the conceptual model of the hydrothermalsystem in the Hammam Faraun hot spring.

Fig. 9. Three-dimensional finite difference blocks for the geothermal numericalmodel of the Hammam Faraun hot spring region.


oriented in a north–south direction, extending 8.5 km in the east–west direction and 9.1 km in a north–south direction. The specialdiscretization was rather coarse, with 31 grid blocks in the east–

west direction (‘‘i’’ index) and 43 blocks in the north–south direction(‘‘j’’ index). Grid-block dimensions varied between 100 m and1000 m in the E–W and N–S directions, with the highest resolutionapplied near the Hammam Faraun hot spring. The model extendedvertically from the ground surface and ranged from +0 m to+500 m above sea level (ASL) to �2000 m ASL. A total of 16 layers(‘‘k’’ index) were used. The thickness of the layers was assigned tobe 100 m ASL and 200 m below sea level (Fig. 10). The uppermostgrid blocks lying above the topography were considered to be ‘‘void.’’

The subsurface strata were assumed to be four layers with dif-ferent physical properties: alluvial deposits, limestone, sandstoneand basement rock (mainly granite). In this study, isotropic perme-abilities were assumed and rock properties other than permeabil-ity (i.e., porosity, thermal conductivity, specific heat and density)were used as the input data to the model. These properties areshown in Table 1 and were considered as the main parametersfor that area. Their values were determined by previous studies,including El-Nouby and Ahmed (2007), El Ramly (1969), Meneisy(1990), and Morgan et al. (1983, 1985).

To calculate the background temperature and pressure distribu-tion of the study area, a steady-state simulation (without intrudinga heat source and fracture parameters) was executed by fixing bothpressure and temperature at the upper boundaries of the litholog-ical units at 1.013 bars and 26.7 �C, respectively. The bottom wasset as impermeable, with a constant heat flux of 120 mW/m2 as aboundary-condition constraint. Lateral boundaries were thermallyinsulated and impermeable.

The results of the simulation show a homogeneous distributionof the subsurface temperatures (Fig. 11). Thus, the output temper-ature and pressure distribution from the steady-state simulationwere used as the initial conditions for the construction of the frac-ture-state model by adding a fracture zone and a heat source at thebottom of the numerical model. The fracture zone was assumed tobe a simple porous medium with different hydraulic properties.

The most important factor in the success of geological modelingis estimating heat sources below a hot spring. Chemical

Fig. 10. (a) Plain view of the finite difference blocks for the comprehensive hydrothermal model of the Hammam Faraun area. (b) The E–W slice shows the subsurface strataof the Hammam Faraun hot spring region, including the fracture and heat source below it.

Table 1Physical rock properties of each layer and the input fracture parameters for the hydrothermal model, in addition to the subsurface temperature and mass flux of the heat sources.

Density (gm/cm3) Porosity (%) Permeability (mdarcy) Thermal conductivity (W/mk) Heat capacity (J/kg K)

Layer (1) 2.4 10 0.0001 2.4 920Layer (2) 2.5 5 0.001 1.3 880Layer (3) 2.4 15 0.01 2.7 920Layer (4) 2.67 1.5 0.00001 1.7 790Fracture 1.5 30 10 0.5 1000Heat source Temperature (�C) Mass flow (kg/s)

180 60


Fig. 11. E–W temperature distribution and water velocity pattern for slice j = 20 of the Hammam Faraun hot spring at a steady-state condition.

Fig. 13. Temperature distribution across the depths of the Hammam Faraun hotspring calculated from the numerical simulation analyses.


geothermometers are the most well-known method for inferringsubsurface temperature, but the Hammam Faraun thermal waterdoes not attain a water–rock chemical equilibrium, which indi-cates a partial equilibrium with the host rock and a possible mixingof different water types (Barragán et al., 2005). Consequently, itwas difficult to use chemical geothermometers with a degree ofconfidence under these conditions. However, the emergence tem-perature at the Hammam Faraun hot spring is known to be 70 �C.Therefore, the model was completed by repeating the simulationsand inserting different values of temperature and mass flow of theheat source until the surface temperature reached this knownvalue (Fig. 12).

The subsurface circulation of geothermal fluids through a gra-nitic-fractured reservoir leads to chemical reactions, includingmineral dissolution and precipitation that affect the fractureporosity and permeability and make the estimation of these valuesdifficult. Hence, by applying different values for fracture perme-ability in the simulation model, we found that the fracturepermeability must not be less than 10 m to reach the steady state(Table 1). Fig. 13 shows the distribution of temperatures with thedepth of the Hammam Faraun region, based on the calculatedtemperatures from the numerical simulation. The temperatureincreases rapidly below the Hammam Faraun hot spring, reaching170 �C at depths less than 2 km, whereas the pressure increasesgradually (Fig. 14).

The numerical simulation succeeded in determining the charac-teristics of the heat sources beneath the Hammam Faraun hotspring and showed that the origin of the hot spring is due to highheat flow and deep-ground water circulation controlled by faults inthe subsurface reservoir. The water velocity increased below thehot spring and flowed upward through fractures and faults

Fig. 12. Near-surface temperature changes in the area of the Hammam Faraunregion (slice j = 20). The calculated temperature equals 73 �C at the emergence ofthe hot spring.

(Fig. 15). The calculated time for the steady-state simulation wasup to 100,000 years and up to 30,000 years for the next simulation(by intruding a heat source at the bottom of the numerical model).Thus, the temperature and pressure distributions in the model didnot change significantly with time. At each block of the model, theywere assumed to represent natural-state (pre-exploitation) condi-tions in the hot spring.

8. Assessment of geothermal potential

The volumetric method is convenient to apply to the first stageof an estimation of the stored heat and recoverable thermal energy.Using the temperature versus depth information obtained from thetemperature gradient map of the Gulf of Suez, the amount of storedthermal energy for a given location could easily be determined.

To apply this method to conventional electric power generation,we employed a limited temperature of 130 �C and assessed theperformance of the reservoir for 30 years of production. The

Fig. 14. Calculated temperature and pressure distributions versus depth below theHammam Faraun hot spring (i = 11, j = 20).

Table 2Parameters used for estimating the geothermal potential of the Hammam Faraun hotspring for conventional electric power production.

Reservoir Temperature �C [Tr] 180Initial Temperature �C [T0] 130Porosity % [Ø] 10%Specific heat of rock kJ/kg �C [Cr] 0.880Specific heat of water kJ/kg �C [Cw] 4.2Density of rock kg/m3 [qr] 2400Density of rock kg/m3 [qw] 900Reservoir volume m3 [V] 0.5 � 2 � 2 km3

Conversion efficiency from heat to electricity % [CE] 10%Availability factor of plant % [Lf] 95%Running period of plant [PL] 30 years


geothermal reservoir was assumed to contain hot solid rock andsingle-phase liquid water. The geothermal potential was calculatedusing the following formula to calculate the total thermal energy inthe rock and water (kJ) (i.e., storage heat) (NEDO, 2005):

E ¼ Er þ Ew ¼ VCrqrð1�uÞðTr � T0Þ þ VCwqwuðTr � T0Þ ð1Þ

This stored heat value is multiplied by a coefficient called therecovery factor to estimate the useful heat that can be extractedfor the abovementioned rock volume. Indeed, only a small fractionof the geothermal energy, determined by Eq. (1), is useful and canbe brought to the surface. The recoverable energy, HR, can be esti-mated by applying a geothermal recovery factor, Rf, to the totalgeothermal resource base as:

HR ¼ E� Rf ð2Þ

The recovery factor depends on the proposed production mech-anism, the effective porosity of the formations and the temperaturedifference between the reservoir and the wellhead. Muffler andCataldi (1978) suggested that the recovery factor for water-dominated geothermal systems depends on the effective porosity

Fig. 15. East–West temperature distribution and water velocity pattern of the Hammamwith vertical and lateral cross sections (slice j = 20).

and permeability and can range up to 25% in some hydrothermalconvection systems. Muffler and Cataldi (1978) suggested thatthe recovery factor for water-dominated geothermal systemsdepends on the total porosity and equals Rf = 1.25u. The usefulextracted heat is then multiplied by the heat to determine thepower-conversion efficiency. The conversion efficiency is the ratioof the generated electricity over the heat extracted from the earth(10%). Higher temperatures yield higher heat for electricity-conversion efficiency. Moreover, the load factor of the power plantwas assumed to be 95% for 30 years. Thus, the potential for powergeneration (MW) was calculated as:

HR � CE=Lf � PL ð3Þ

The parameters for Eqs. (1)–(3) are defined in Table 2.The value of the estimated geothermal potential for the

Hammam Faraun hot spring area was 19.8 MW for an assumedreservoir thickness of 500 m. With the same thickness, the initialtemperature was 130 �C, and the performance of the reservoirwas assessed for 30 years of production. Additionally, thegeothermal reservoir was assumed to contain hot solid rock andsingle-phase liquid water.

This geothermal resource is typically used for direct-use appli-cations, such as district heating, greenhouses, fisheries, mineralrecovery, and industrial-process heating. However, a low-enthalpyresource can be harnessed to generate electricity using conven-tional binary-cycle electricity-generating technology. The resultingpower electricity would be sufficient for the desalination of waterfor both human and agricultural consumption. This could be usedfor sustainable development in the Sinai Peninsula.

Faraun hot spring at a natural state, including the fracture and heat source below


9. Conclusion

The processing and analyses of the gravity and MT data ac-quired from the Hammam Faraun region permitted us to charac-terize the subsurface density and electric structure of the area.The forward modeling of the gravity data seemed to work effi-ciently and was capable of delimiting the interface between thebasement rock and sedimentary cover. Additionally, the 1D and2D inversion results of the MT data revealed the existence of a highresistivity body at shallow depths (>1000 m) below the HammamFaraun hot spring. Therefore, our results could be used to deter-mine the origin of this hot spring, where the highly resistive anddenser regions reflect the basement structure. Conceptual model-ing and numerical simulations of the Hammam Faraun hot springshowed that the origin of the hot spring is derived from high heatflow and deep circulation of the underground water controlled byfaults that are associated with the opening of the Red Sea and Gulfof Suez rifts. The uplifted basement is the site of the high heat flow.A simulation of the Hammam Faraun hot spring using HYDRO-THERM led to a better understanding of the observed processes.The value of the estimated potential for electric generation was19.8 MW. This value would be sufficient for the desalination ofwater for both human and agricultural consumption and couldthereby be used for sustainable development in the SinaiPeninsula.

Acknowledgements

This work is the result of a joint effort of the National ResearchInstitute of Astronomy and Geophysics (NRIAG) in Egypt and theGeothermic Laboratory of Kyushu University, Japan, with the assis-tance of the Global COE (Center of Excellence) in Novel Carbon Re-source Sciences, Kyushu University.

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journal of asian earth sciences - wordpress.comfig. 1. topography of the gulf of suez region from...

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