الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 139 |  |  |
| | | from | 139 | | |
Abstract
To understand the tectonic evolution and the reservoirs characterization of the Razzak Area, twenty 2D highly filtered stack zero-phase seismic sections and four well logging data were analyzed. In addition, 3D models of the North Razzak Area were built based on integrated geological and petrophysical data.
The seismic interpretation of the Top Jurassic indicates the presence of a group of normal faults trending ENE/NE-WSW/SW and dipping to SE and NW. Two main normal faults forming horst-form structure, each one consists of interlinked segments. These faults coincide with the Jurassic rift trend (Mesozoic Tethys Rift) attributed to the northwest divergent movement between Afro-Arabian and Eurasian plates. These faults are associated with differential vertical displacement. These faults are also dissected by a number of normal faults trending NW-SE, which may be associated with the Early Cretaceous rifting (Aptian-Albian).
The NE Jurassic faults continued during the deposition of the Early Cretaceous Alam El Bueib Formation as growth faults, where thicker sediments found at the hanging-walls in comparison to foot-walls. The seismic interpretation shows that the structural setting of Alamein reflector is the same as that of the Jurassic Masajid Formation. The ENE/NE faults had been rejuvenated or continued during the closure of the Neotethys Ocean. During the Late Cretaceous, the compressional stress resulting from the collision between African and Eurasian plates has developed many compressional structures (Syrian Arc System). The latter led to the inversion of the Razzak basin, where some segments of the main faults are transformed from normal to reverse and the hanging walls formed plunging anticlinal folds dissected by a set of NW-SE normal faults.
The maximum height of the F1 fold is achieved in the southeastern part reaching 1360 ms and -6500 ft, and the maximum height of the F2 fold is achieved in northwestern part reaching 1530 ms and -7200 ft. According to the interpretation of the seismic sections and structure contour maps (both time and depth), there are four closures in Razzak Field; the first one is Main Razzak. It is found at the downthrown side of F1. The Seconde closure in Razzak field is North Razzak. It is found at the downthrown side of F2. The third closure is the West Razzak. Such closure is not well identified due to the lack of data. Also due to the lack of data the fourth closure (East Razzak) is not well identified.
The petrophysical analyses of the four wells (NRZK-1, NRZK-2, NRZK-3, and NRZK-4) indicated that Alamein Formation (mainly dolomite) is a good reservoir and can be subdivided into two zones. The first zone is Upper Alamein and the second one is Lower Alamein. This classification was based on the integrated logging tools (e.g., Gamma Ray, Sonic Log, Resistivity Deep, Neutron Porosity, and Bulk Density). The gross thickness of the Alamein Formation ranged from 220 to 238 ft, the net thickness is ranging from 207.75ft to 226.5 ft, and net/gross from 0.88 to 0.9. In Upper Alamein, the gross thickness range from 168.98 to 184.48 ft, the net thickness from 168.61 ft to 183.29 ft, and the net/gross from 0.88 to 0.91. The thickness increase toward the central part of the study area.
Shale content is considered as an important indicator of reservoir quality, in which the lower the shale content usually reveals a better reservoir. The calculated shale volume of the Alamein reservoir ranges from 3.1% to 16.1% and in Upper Alamein 0.5% to 4.4%. Another important property is effective porosity that ranges from 4.78% to 7.3% and increases to the East direction. The water saturation calculation is important as it is an indicator of the value of hydrocarbon saturation, at Upper Alamein ranges from 18.1% to 23.9%, consequently, the hydrocarbon saturation ranges from 76.1% to 81.9%. AEB-3 needs to be tested by other wells since the drilling reports stated that it has oil shows but well logs don’t reflect that. Unfortunately, some formations may be considered as good reservoir rocks and their petrophysical properties such as effective porosity, shale volume are valuable, but water saturation disturb that. For example, Kharita Formation, Alam El Buib members (AEB-4, 6, 8, 10).
The structure framework was completed by using the 2D seismic to interpret the Alamein Formation depth map to be used in building the 3D structure model. According to the reservoir characterization changes, the Alamein Formation was subdivided into main two zones from the top (Upper Alamein and Lower Alamein) and 20 layers to capture the petrophysical changes. The Alamein Formation deposited in a shallow marine environment as limestone and later subjected to diagenetic proceses (dolomitization) to be compose mainly of dolomite and dolomitic limestone. The core data and wireline logs were used to identify the detailed facies logs, where NRZK-3 and NRZK-1 wells composed mainly of dolomitic limestone and toward the eastern part of the lithology changed to be pure dolomite as in NRZK-4 and NRZK-2 with approximately 185 ft thickness. The proportion analysis showed a generally slightly equaled the percentage of dolomite in comparison to dolomitic limestone units. The petrophysical properties were analyzed and distributed in a 3D model. These properties were total porosity, effective porosity, water saturation, and hydrocarbon saturation. The Upper Alamein Zone has better properties than the Lower Alamein Zone. Therefore the Upper Alamein Zone can be considered as a commercial oil zone.