الفهرس 
GEOLOGIC SETTING OF THE STUDY AREAOnly 14 pages are availabe for public view
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Abstract
Although Egypt is not characterized by abundant Cenozoic igneous activity, its location in the northeastern corner of the African Plate suggests that it may possess geothermal resources, especially along its eastern margin. The most promising areas for geothermal development in the North West Red Sea/Gulf - of- Suez rift system is located where the eastern shore of the Gulf of Suez is characterized by superficial thermal manifestations including a cluster of hot springs with varied temperatures.
The purpose of the present study is to assist the geothermal potential of the study area in order to evaluate the possibility of exploitation of this geothermal energy. This aim could be achieved through integration between gravity implications and geothermal manifestations in detecting the main subsurface structures in addition to expecting the geothermal sources in the area under consideration. Accordingly, a conceptual geothermal model of the study area could be generated.
The study area is selected to be located at the Southeastern part of Gulf-of-Suez with Latitude from 28o 00′ 00″ to 28o 30′ 00″ N and Longitude 33o 00′ 00″ to 33o 40′ 00″ E and covers an area of about 3800 km2.
Topographically, the Gulf-of-Suez is flat-bottomed with a depth ranging from 55 to 75 m. At its mouth, the Gulf descends to a depth five times its own and is thus a shallow shelf filled with the surface water of the Red Sea. The geology of the area ranges from Precambrian basement rocks to the Quaternary deposits. The basement rocks (Precambrian) occupy the southern part of the study area, along the Gulf-of-Suez and Gulf-of-Aqaba.
On the other hand, the Paleozoic rocks are present in the middle part while the Mesozoic rocks cover the eastern and western parts of the area.
Gravity data in the form of Bouguer anomaly map was used to infer the geologic characteristics and delineate the subsurface structures of the study area. To enhance the structural features from the sedimentary and basement rocks in the study area, gravity data was isolated into regional and residual components. The separation process was performed using Griffin method (1949) to identify the residual features from those of regional nature at different depths from 1.0 km to 4.0 km.
Trend analysis and fault depths interpreted from Bouguer and regional gravity maps in addition to residual gravity maps show the same tectonic trend for shallower and deeper sections which gives an indication to vertical uplift movement rather than the lateral compression. This is clear from the predominant NW-SE trend of the Red Sea/ Gulf-of-Suez.
Moreover, three dimensional gravity inversion was performed to get a comprehensive picture about the subsurface structure of the study area, the model is based on two-layer case; sedimentary layer which is assumed to be of average density 2.4 g/cm3 and basement layer of average density 2.67 g/cm3. The model of covers 3800 km2 and is oriented in a north–south direction, extending 64 km in the east–west direction and 56 km in a north–south direction. The calculated depths of basement rocks that extracted from 3D modeling of gravity data are matched with true depths from some oil wells (GS-352, SB-296 and SB-276). Additionally, the E-W section along Hammam Musa hot spring suggested that the origin of hot spring is due to uplift of the basement rock.
Furthermore, it is inferred from the gravity inversion that the depth of basement in the study area ranges from 1 to 4.4 km. Interpreting the depth of basement map highlights three interesting locations with markable basement uplift which are: The main trend of Gulf-of-Suez, especially around Hamam Musa with depth ranges from 1 to 1.2 km, Ras Gharib with depth ranging from 2.2 to 2.4 km and Ras Dib with depth ranging from 2 to 2.2 km.
On the other hand, a geothermal approach in the form of bottom-hole temperatures (BHT) are used in an attempt to assist the geothermal potential of the southern part of Gulf-of-Suez-Sinai region based on the bottom hole temperature logs of 72 onshore and offshore deep oil wells. Bottom Hole Temperature Logs (BHT) were corrected, using two Waples and Horner methods, to obtain the true Formation Temperature (FT), which is an essential parameter to determine the temperature gradient and heat flow.
The temperature gradient and heat flow maps showed that the mean geothermal gradient of the area is 0.032 (°C/m) while the maximum gradient found to be 0.045 °C/m around Hammam Musa and Ras Gharib areas. The regional heat flow of the study area is ranging from 45 to 115 mW/m2 while the maximum values were encountered near Hammam Musa and Ras Gharib areas is 117.13 mW/m2.
Integration of geophysical data and geothermal data shows a good correlation between areas of high heat flow and positive gravity anomalies which implies that the geothermal potential in the southern part of Gulf-of-Suez is controlled by uplifts and faults on the basement rocks. On other words, the uplifted basement is the site of high heat flow.
Thus, this result can be used also for eliciting the source of Hammam Musa hot spring that is due to tectonic uplift of hotter basement rocks causing deep fluid circulation through faults on the surface of the basement rock. Such faults allow the formation of discharging conduits for water ascending from depth after being heated and mixed with other water type.
Moreover, a relation between geothermal gradient and maturation of hydrocarbons revealed that high temperature gradients cause to expedite the formation of oil at relatively shallow depths and narrow oil windows. While, low temperature gradient makes the oil window to be quite broad at located at high depths.
Finally, the calculated geothermal potential of the geothermal system of the study area is 51 MW, taking into consideration the least thickness of the geothermal reservoir which is 0.5km. However, the geothermal reservoir could be of larger thickness. Additionally, generating electricity from low-to-medium temperature geothermal fluids through binary plant technology is a very effective and reliable mean for converting the energy available from water-dominated (85-170°C) geothermal fields into electricity.