الفهرس 
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Abstract
In this study, the Oligocene-Miocene sequence was studied in the five wells, three of which are located at the northeastern reaches of the Nile Delta (Boughaz-1, El- Temsah-2 and San El-Hagar-1). While the last two wells are located at the northwest Sinai region (Bardawil-1 and Malha-1).
A total of 138 subsurface ditch samples were collected from five wells, (25 samples from the Boughaz-1 Well, 25 samples from the El-Temsah-2 Well, 25 samples from the San El-Hahar-1 Well, 51 samples from the Bardawil-1 Well, and 12 samples from the Malha-1 Well).
Five rock units were defined in this succession and arranged from the top to base as follows:
1- Qawasim Formation: its age is (latest Miocene, late middle Miocene, and latest early-middle Miocene) in the Boughaz-1, El-Temsah-2, and San El-Hagar-1 wells respectively. This unit conformably overlies the Sidi Salem Formation in the Boughaz-1 and El-Temsah-2 wells and conformably overlies the Kareem Formation in the San El-Hagar-1 Well.
2- Sidi Salem Formation: its age is (latest Middle-late Miocene, early middle Miocene, late Miocene, and middle Miocene) in the Boughaz-1, El-Temsah-2, Bardawil-1, and Malha-1 wells respectively. It unconformably overlies the Rudeis Formation in the Boughaz-1 Well, and conformably overlies the Qantara Formation in the El-Temsah-2 Well, only part of which was studied in the Bardawil-1 Well, and it unconformably overlies the Qantara Formation in the Malha-1 Well.
3- Kareem Formation: early Miocene in the San El-Hagar-1 Well and conformably overlies the Rudeis Formation.
4- Rudeis Formation: it has late Early-Middle Miocene age in the Boughaz-1 Well, and early Miocene in the San El-Hagar-1 Well. It lies conformably above the Qantara Formation and unconformably below the Sidi Salem Formation in the
Boughaz-1 Well and it lies conformably above and below the Qantara and the Kareem formations, respectively in the San El-Hagar-1 Well.
5- Qantara Formation: it is ranged in age from the late Oligocene-early Miocene in these studied wells. It unconformably overlies the late Cretaceous formations in the Boughaz-1 Well, and it conformably underlies the Rudeis Formation in the Boughaz-
1 and San El-Hagar-1 wells. In the El-Temsah-2 Well, the Qantara Formation conformably underlies the Sidi Salem Formation, but in the Malha-1 Well, it unconformably overlies and underlies the late Cretaceous formations and the Sidi Salem Formation, respectively.
63 nannofossil species were identified, belonging to 17 genere and 10 families. Twelve calcareous nannofossil biozones of the late Oligocene-late Miocene were defined and correlated with their relevant biozones in Egypt and other parts of the world. These biozones are arranged from the top to base as: Amaurolithus tricorniculatus Zone (NN12), Discoaster quinqueramus Zone (NN11), Discoaster calcaris Zone (NN10), Catinaster coalitus Zone (NN8), Discoaster kugleri Zone (NN7), Discoaster exilis Zone (NN6), Sphenolithus heteromorphus Zone (NN5), Helicosphaera ampliaperta Zone (NN4), Sphenolithus belemnos Zone (NN3), Discoaster druggii Zone (NN2), Sphenolithus ciperoensis Zone (NP25), and Sphenolithus distentus Zone (NP24).
According to the defined biozones, the middle/late Miocene boundary cannot be detected in any studied well due to the absence of the Discoaster hamatus Zone (NN9). While the early/middle Miocene boundary can be placed at the top of the Zone (NN4). In this study, the Miocene rocks unconformably overlie the Oligocene sediments and this unconformity surface represented by the absence of the calcareous nannofossil Zone (NN1). So, the Oligocene/Miocene boundary can be drawn unconformably at the top of the Zone (NP25).
The mineralogical composition of 28 clastic and non-clastic samples selected from the Nile Delta and North Sinai areas has been determined using X-Ray Diffraction technique (XRD). The mineral contents were carried out and a semiquantitative determination of the minerals was conducted based on measuring peak height ratio (Carver, 1971).
The sediments of the Nile Delta area are mostly clastics and composed mainly of sandstone and shales. Mineralogical analyses were carried out on (18) samples selected from the subsurface different rock units in the Nile Delta wells (Boughaz-1, El-Temsah-2 and San El-Hagar-1), and (10) samples selected from the subsurface different rock units in the North Sinai wells (Bardawil-1 and Malha-1).
Generally, the bulk rock mineralogy of these wells indicates the abundance of quartz and Kaolinite of clay minerals with few feldspars. Calcite frequently occurs with small amounts of Gypsum. Dolomite and muscovite are present in minor amounts.
Mineralogical analyses were carried out on (10) samples selected from the subsurface different rock units in the North Sinai wells (Bardawil-1 and Malha-1).
The data of its bulk rock analysis showed that kaolinite, quartz, feldspars and calcite are the main constituents beside other minor minerals such as, dolomite, and rarely gypsum, mica, zeolite and ankerite.
Generally, the Miocene sediments of the three studied wells in the Nile Delta area (Boughaz-1, El-Temsah-2 and San El-hagar-1), are dominated by kaolinite and quartz more than the other wells in the North Sinai area (Bardawil-1 and Malha-1). The lower-middle Miocene sediments in the all studied wells relatively contain high carbonate content than those of the upper Miocene.
The predominance of carbonates that deposited in the lower-middle Miocene sediments in the studied wells indicates that they laid down in the inner shelf which led to the reduction of terrigenous influx allowed calcareous organisms to flourish and resulting in carbonate production.
Organic geochemical investigations based on TOC and Rock-Eval pyrolysis analyses were carried out on 19 cuttings samples collected from the shales of different studied formations in the both Nile Delta (13 samples) and North Sinai wells (6 samples) to evaluates the petroleum potential of source rocks in the Oligo-Miocene succession in these two areas.
The Rock-Eval pyrolysis and TOC results indicated that all the studied formations in both two areas, depending on temperature, are immature source rocks. In the Nile delta area, Qawasim, Sidi salem and Qantara formations (El-Temsah-2
Well) are organically-rich and have a good petroleum potential (kerogen Type II – oil- prone), while Sidi Salem (Boughaz-1 Well), Rudeis and Qawasim (San El-Hagar-1 Well) formations are a poor petroleum potential (kerogen Type III - gas-prone) and Qantara Formation (Boughaz-1 and San El-Hagar-1 wells) has a moderate petroleum potential (Mixed kerogen Type II/III – oil-gas-prone). On the other hand, Qantara Formation in the North Sinai area has poor petroleum potential (kerogen Type III - gas-prone) and Sidi Salem Formation (Bardawil-1 Well) is a good petroleum potential source rock (kerogen Type II – oil-prone).