GEOCIENCIAS-VOL 14-1 2010.vp EARTH SCIENCES RESEARCH JOURNAL Earth Sci. Res. J. Vol. 14, No. 1 (June 2010): 44-62 GEOPHYSICAL CONTRIBUTION TO EVALUATE THE HYDROTHERMAL POTENTIALITY IN EGYPT: CASE STUDY: HAMMAM FARAUN AND ABU SWIERA, SINAI, EGYPT Magdy A. Atya1, Olga A. Khachay2, Aiman Abdel Latif1, Oleg Y. Khachay2, Gad M. El-Qady1 and Ayman I. Taha1 1 National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt. 2 Institute of geophysics UD RAS, Ural’s state University, Russia. ABSTRACT The geothermal potentiality in Egypt has a minor significance in the aspects of the Egyptians life, while the hydraulic and hy- drocarbon resources are more convenient. However, some other applications for the geothermal activity such as direct warm- ing, pools, and physiotherapy make the research for geothermal as requested. In the present work, two locations with rather good geothermal potentiality will be studied; these are Hammam Faraun and Abu Swiera (water temperature is about 70 °C; at Sinai Peninsula). The contribution of the geophysical techniques to evaluate such potentiality could be considered, as its capability to identify the reservoir characteristics and its implementation is acceptable. Therefore, a geophysical survey program has been con- ducted in terms of seventeen vertical electrical soundings (VES) and two wide profiles of Control Source Electromagnetic (CSEM) forward step at Hammam Faraun and two wide profiles of CSEM at Abu Swiera. The geophysical techniques yield in- formation on the spatial distribution of electrical conductivity, which is the most sensitive parameter to fluids in the rocks. The analysis of the geophysical data, together with the field and geochemical studies lead to the conclusion that, the thermal water in the subsurface formations might be considered as the preferred cause of the high conductivity in the subsurface on/close to the boarder of tectonically active regions, particularly, where the anomalous conductivity is correlated with high heat flow and other geophysical and geological parameters. Key words: Hammam Faraun, Abu Swiera, vertical electrical soundings, control source electromagnetic, conductivity of subsurface. RESUMEN La potencialidad de la energía geotérmica en Egipto tiene una importancia menor en los aspectos de la vida de los Egipcios, comparado con los recursos hidráulicos y de hidrocarburos. Sin embargo, algunas aplicaciones de la actividad geotérmica, como el calentamiento directo, las piscinas y la fisioterapia, hacen de la investigación de la energía geotérmica necesario. En el presente trabajo, dos localidades con potencialidad geotérmica bastante buena serán estudiados; éstos son Faraun y Abu Hammam Swiera (la temperatura del agua es de aproximadamente 70 °C, en la península del Sinaí). 44 Manuscript received: 03/02/2010 Accepted for publication: 14/04/2010 Debe considerarse la contribución de las técnicas geofísicas para evaluar el potencial así como la capacidad para identificar las características del reservorio, y su aplicación. Un programa de prospección geofísica se realizó por medio de diecisiete Sondeos Eléctricos Verticales (SEV) y dos de gran perfil con fuente Electromagnética controlada (CSEM) en Hammam Faraun y dos grandes perfiles CSEM en Abu Swiera. Las técnicas geofísicas muestran información sobre la distribución espacial de la conductividad eléctrica, que es el parámetro más sensible a los fluidos en las rocas. El análisis de los datos geofísicos, junto con el campo y los estudios geo-químicos llevan a la conclusión de que, el agua termal en las formaciones del subsuelo podría ser considerada como la causa de la alta conductividad en el subsuelo o cerca del borde de la regiones tectónicamente activas, en particular, donde la conductividad anómala se correlaciona con el alto flujo de calor y otros parámetros geofísicos y geológicos. Palabras clave: Hammam Faraun, Abu Swiera, sondeos eléctricos verticales, control de código fuente electromagnética, conductividad de superficie. 1. Introduction Two sites have been selected to study the geothermal occur- rences in the central part of Sinai Peninsula; Hamam Faraun and Abu Swiera close to the Gulf of Suez (Figure 1). As shown, the studied areas are located on the eastern side of the Gulf of Suez region which represents one of the most prolific and prospective oil provinces in Egypt. The area in- cludes a number of oil fields such as Assel oil field. Hamam Faraun lies at 29° 11´ 55.18``N and 32° 57´ 18.64´E and the elevation is about 9 m above sea level, while Abu Swiera area lies 29° 32´ 47.44``N and 32° 48´ 38.60´E and the ele- vation is about 44 m above sea level. To spot more light on Hamam Faraun and Abu Swiera Hot Springs, we carried out Vertical Soundings (VES) and an approach to utilize planshet Control Source Electromagnetic (CSEM) wide-pro- files crossing the geothermal active fields. The main aim of this study is to analyze the geophysical, geochemical, and also the geological feed back in order to define the signifi- cant tectonic patterns, which are responsible for the struc- tural development of the geological units at the area of study. The study resulted in understanding of the hydro-geother- mal regime at Hammam Faraun and Abu Swiera through the evaluation of the subsurface imaging and the capability for investment projects. 2. Geology and tectonics of Central Sinai Peninsula The central part of Sinai province represents a tectonic spe- cific belt put it as one of the most prolific and prospective oil provinces in Egypt. In the early tertiary period (Oligocene - Miocene), where the opening of the Red sea rift, some volca- nic activity took place. In western and central Sinai, there are a number of basaltic bodies mostly of doleritic dikes, sills and plugs; flows are known near to Abu Zenima and Hammam Faraun (Meneisy, 1990). The major geological structural feature of the study area is a well-defined fault block oriented NNW-SSE, which tilts strongly eastward on its western side. Also there is a fault escarpment overlook- ing directly the Gulf of Suez and rising about 300 m above the Gulf (El-Shinnawi, and Sultan, 1973). Hamam Faraun area is one of more vigorous topogra- phy because of the presence of several local mountain ar- eas (Gebel Hammam Faraun and Gebel Tall) of altitudes varies from 50 to 480 m above sea level. The shallow geo- logical succession in Hamam Faraun area (Fig. 2) could be, mainly, distinguished into the following formation (Said, 1962): 1. Post-Pliocene composed of sand and conglomerate of about 50 m thickness. 2. Pliocene rocks, differentiated into sand, sandy lime- stone, and lagoonal gypsum deposits of thickness about 50 m. 3. Miocene and Oligocene rocks which composed of gypsum, sandy marl and conglomerate with total thickness of about 70 m. 4. Eocene rocks of total thickness 100m, which can be differentiated into, upper Eocene of limestone and sandstone, Middle Eocene of shale and lime- stone, and Lower Eocene of chalk and flinty lime- stone. 5. Upper Cretaceous rocks which are composed of shale with minor limestone. As for Abu Swiera hot spring, from the geological point of view, the area is a triangular excavation represents the synclinal trough to the southwest of El-halal anticline massif. 45 GEOPHYSICAL CONTRIBUTION TO EVALUATE THE HYDROTHERMAL POTENTIALITY IN EGYPT: CASE STUDY: HAMMAM FARAUN AND ABU SWIERA, SINAI, EGYPT The head of this triangle is directed northward while its base measures a length of about 25 km facing Gebel Kharim in the south. The length of this plain attains about 50 km. Its ground elevation decreases northward from 300m at its base to about 190 m at its apex. The surface of these plains is dotted by nu- merous mesas and buttes, which formed of early Eocene lime- stone with cherty bands. This surface is dominated by washed, dark angular to sub-angular cherty and limestone fragments. Locally, these plains are covered by active sand dunes, which form several lines of isolated branches. The area is controlled by three different tectonic provinces related to northern part of the African plate (Said, 1962). These are the northern Egypt fold belt, NE-SW (Syrian arc system) and the Suez rift which is younger than north Egypt fold belt, is domi- nated by NW to NNW oriented normal faults. 3. Hydrothermal regime at the study sites At Hammam Faraun, the spring issues thermal water at the foot of the Gebel from fractured karstifed dolomitic Eocene limestone Formation. The spring seepages were estimated to 880 m3/d (El- Ramly, 1966), 3000 m3/d (Himida and Diab, 1976). These seepages are drained through minor channels mixed with the gulf water. The thermal seepages are tested from Hammam Faraun cave. H2S gas is present with its characteristic odor. The ther- mal water seepage and flow toward the gulf water. Issar et al. (1971) proposed a thermal flow mechanism in which a sequence of aquifers is interconnected by means of a sys- tem of faults and fractures zones, resulting in the occur- rence of springs at the surface. The contribution of various aquifers to the total outflow of spring is regulated 46 MAGDY A. ATYA, OLGA A. KHACHAY, AIMAN ABDEL LATIF, OLEG Y. KHACHAY, GAD M. EL-QADY AND AYMAN I. TAHA MEDITERENEAN SEA BAHARIYA OASIS OASIS OASIS OASIS DAKHLA KHARGA G U L F O F S U Z E RED SEA Eastern Desert Western Desert FARAFRA CAIRO 29 00 ` 00 `31 33 00 ` 3500 `27 00 `25 00 ` 31 00 29 00 27 00 25 00 QATTARA DEPRESSSION Ayun Musa Ain Sukhna 12 9 6 13 10 11 8 15 167 5 4 3 1 2 14 Scale :- 0 40 80 100 Km. Legend:- Hot wells Hot springs 32° 42’ 17” 32° 58’ 09.78” 29° 39’ 27.57” Ras Sidr Abou Swira 29° 11’ 29.40” Gulf of Suez Scale Hammam Faraun 0 13.5 27 km 32° 58’ 09.78” N W E S Figure 1: Location map of the studied area. 47 GEOPHYSICAL CONTRIBUTION TO EVALUATE THE HYDROTHERMAL POTENTIALITY IN EGYPT: CASE STUDY: HAMMAM FARAUN AND ABU SWIERA, SINAI, EGYPT Ras Sudr Ras Matarmah Legend Gulf of Suez Ras Malab Abu Aggag Fm. Duwi Fm. Esna Fm. G. El-Ahmar Fm. Gharandal Group Matulla Fm. Ras Malaab Group Sabkha deposits Sudr Fm. Tertiany Alkali Olivine Basalt Thebes Group/Egma Fm. Wadi Deposits Alluvial Deposits Scale 0 7,000 14,000 28,000 Meters Figure 2: Geologic map of the studied area. by their relative and absolute potentials. All the pressure in these formation caves depleted with time, an Eocene aquifer located at higher level began to flow and contin- ues to do so to the present day. ElRefeai (1992) and El-Kiki et al. (1992) carried out a cluster analysis of the hydrochemical variables for wells and springs tapping the deep aquifers in the Gulf of Suez region. The produced dendrogram differentiate the Eocene aquifer from the underlying (Nubia aquifers) and the overlying Miocene one. In this dendrogram the Hammam Faraun spring was designated as a member in the cluster of Eocene aquifer in the region.The underlying Esna shale is considered as the aquiclude, which separates the Eocene beds from the underlying aquifer (Nubia). However, the interconnection through the faults and frac- ture zone should not be completely disregarded. Issar et al. (1971) conceived an evaluation history of the forma- tion waters in the Gulf of Suez region which the Eocene aquifer is a product of mixing, through fracture system, between ancient seawater and Pleistocene meteoric water. Unfortunately, no more work related to Abu Swiera hot spring. 4. Approach to use the Control Source Electromagnetic (CSEM) Concept of CSEM The demand to the enhanced geophysical technique and de- vice, in addition to the precise analytical interpretation of the geophysical data, is the resolution of the geophysical com- plex research, especially by the absence of priory informa- tion about the researched place. The device for use the planshet method of electromagnetic induction (Hachay O. A., 1997a, Hachay O. A. and Bodin, 1997b, Hachay O. A. et al., 1999, and 2000, Hachay O. A., 2002 ) in the frequency domain was developed by Chelovechkov A.I. The method was adapted to map and monitor the high complicated geo- logical mediums, to determine the structural factors and cri- teria of stability of the rock massif in the mine subsurface. The field observation and the way of interpretation make the new technology differ from other known earlier methods of field raying or tomography (Hachay O. A. and Novgorodova E. N., 1997c, Hachay O. A. et al., 1999, and 2000, and Lau K.H., and Cheng P. 1977). The concept to research the 3D geoelectric medium is based on interpreting the alternating electromagnetic field in the frame of a block-layered isotropic medium with inclu- sions over three stages (Hachay 1997a, and 2002); in the first stage, the geoelectric parameters of the horizontal block-layered medium, which includes the block heterogeneities, are defined, in the second stage, a geometri- cal model of the different local heterogeneities or groups in- side the block-layered medium is constructed based on the data of local geoelectrical heterogeneities, while in the third stage, the surfaces of the searched heterogeneities could be calculated in account of the physical parameters of the anomalous objects. Obtainable field data For practical realization of that conception, the system of ob- servation for alternating electromagnetic field with use of vertical magnetic dipole was elaborated. Such local source of excitation and regular net of observations allows realizing overlapping by different angles of observation directions. As incoming data for interpretation, modules of three com- ponents of magnetic field are used. For the case on surface observations the data are measured on the Earth’s surface at the set of distances between the source and receiver as a function of frequencies. The measurements of the module of three components of the magnetic field (vertical ��z� and two horizontal: one directed to the source �Hr� and second perpendicular to that direction �Hö�) are provided in the frame of planshet for the fixed net with fixed step and fixed length of the planshet’s side. In the frame of profile observa- tions the planshet become to a band or a line and the length of the band or the line is a base of observations or an array. For the variant of the wide profile (band) the source of exci- tation is located at the beginning of the array on the profile, which is parallel to the measured profile. We shall call that a wide array. It moves systematically with a fixed step of me- ters. For the variant of a usual profile the source is located on the measuring profile and the moving of the oscillator is sim- ilar. For the variant of a planshet survey the source is located into the center of the planshet using the fixed net of observa- tion. Then the planshet array moves systematically with overlapping usually on the half of the planshet. Processing and interpretation of CSEM data For each array and fixed frequency ù two interpretation pa- rameters are defined: ñeff (r)=ùr2(�Hz�/�Hr�)/ð ä(r) =(�Hö�/�Hr�)100%. Where ñeff (r) is the apparent resistivity, r is the distance between the source and the point of observation, ù is the fre- quency f multiplied by 2ð, �Hz� is the module of the vertical 48 MAGDY A. ATYA, OLGA A. KHACHAY, AIMAN ABDEL LATIF, OLEG Y. KHACHAY, GAD M. EL-QADY AND AYMAN I. TAHA magnetic component, �Hr� is the horizontal component of magnetic field oriented to the source, ð = 3.14, ä(r) is the pa- rameter of geoelectrical heterogeneity, and �Hö� is the sec- ond horizontal component of magnetic field perpendicular to the direction of the source. That data are the information base for the further inter- pretation. On the first stage we define the geoelectrical pa- rameters of the 1-D section for each array and each frequency after the preliminary filtration of the data: ñeff (r): ä(r)