الفهرس 
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Abstract
Nile Delta region has a relatively complex geological history, marked by repeated episodes of tectonic uplift and subsidence due to its position on the active northern margin of the African Plate. As part of the Nile Delta, the study area is located approximately 60 km offshore from the central Nile Delta. It is in water depths ranging from 70 m to 100 m. This area suffered from a complex geological history during Mesozoic. It was affected by rifting in north-west to south-east direction that led to the formation of half graben-like basin. The Oligocene compression activated the pre-existing structure fabrics and led to the formation of a positive flower structure.
Exploration in the Oligocene section is still in an early stage across the offshore Nile Delta due to complex geologic setting and poor seismic imaging. Since the beginning, the exploratory activities in the offshore Nile Delta aimed to investigate the hydrocarbon potential of the Tertiary sequence with particular reference to the post-Messinian section. Lately, the discovery of commercial hydrocarbon accumulations in the Oligocene interval encourages some exploration companies to drill wells reaching this interval (i.e., rare wells have been drilled so far due to high temperature high pressure conditions of the Oligocene section that make the drilling becomes more difficult and expensive). So, the purpose of this work is the studying the reservoir characteristics of the main reservoirs of Oligocene (Rupelian) section and identifying the depositional elements of these reservoirs by integrating different types of data such as seismic, cuttings, cores and well logs.
The study of reservoir system (O15 and O18 reservoir packages) was challenging due to existence of bad seismic data imaging (i.e., mud volcano, tuning thickness, Messinian complexity and low signal to noise ratio). Only three wells penetrated the Rupelian section at the western and southern central parts of the area and no penetrations have been made at the eastern part of the area. The lack of penetrations in the eastern area made the understanding of the reservoir characteristics difficult for this area. All wells penetrated O18 reservoir package but only one well (X2-well-OH) penetrated top of O15 reservoir package. Additionally, the absence of core captured from O15 interval limit the identification of reservoir characteristics and its rock quality.
The present work concerns with; Firstly, understanding the tectonic setting and structural development of the study area. Secondly, identification of architectural elements of individual reservoir packages (O15 and O18) of the early Oligocene (Rupelian) interval and building O15 and O18 depositional models. Thirdly, evaluating the petrophysical properties of early Oligocene interval (pre-O20 interval) and studying reservoir characteristics and rock quality based on previously calculated petrophysical properties, cuttings description and core analysis. Finally, integrating well data analysis and attribute-based depositional models for reservoir characterization and investigating the reservoir connectivity. These objectives have been achieved through the following studies:
1. Description of the geology of the Nile Delta, with emphasis on the study area such as discussing the regional stratigraphy of the Nile Delta, with special reference to the study area, illustrating the structural framework of North Nile Delta, discussing the structural evolution of the study area and understanding the tectonic history of offshore Nile Delta and its impact on the study area (Chapter 2).
2. Discussing the Turbidite systems including their definition, generation, components of turbidities ”Bouma Sequence”, deep-marine depositional System of turbidite and the produced depositional models (Chapter 2).
3. Tying the synthetic seismogram to the reflectivity volume then mapping the top (O20_FS) and base of the interesting part of Rupelian section (O00_SB) then identifying flooding events (O15_FS and O18_FS) within this interesting part of the Rupelian section based on the seismic and well data then mapping these flooding surfaces (O15_FS and O18_FS) (Chapter 3).
4. Generating coherence volume to aid in understanding the structural fabrics (elements) affecting the study area then making O00_O20 isochrone map to give us an idea about the major structural features affecting the study area based on lateral thickness variation (in time) of the Rupelian section (Chapter 3).
5. Mapping the top and base surfaces of O15 and O18 reservoir packages to use these surfaces in initiating the reservoir isochores (O15 and O18 isochrones) and different attribute maps (Chapter 3).
6. Creating different amplitude attribute maps, horizon-based coherence maps, edge detection maps, and composite spectral decomposition images for O15 and O18 reservoir packages to be used in architectural elements identification and building O15 and O18 depositional models (Chapter 4).
7. Evaluation of petrophysical properties of early Oligocene interval (pre-O20 interval) and integrating depositional models based on attribute maps, core, cuttings description and petrophysical properties for understanding the reservoir characterization for O15 and O18 reservoir package (i.e., no cores encountered at O15 reservoir package) (Chapter 4).
The results obtained from this study are as the following:
1) The produced time maps (O00_SB, O15_FS, O18_FS, O20_FS, O15_TRP, O15_BRP, O18_TRP and O18_BRP) display the same structural fabrics which is a large four-way anticline with a NE-SW bounding fault, parallel to Rosetta fault trend, affecting the Rupelian section. O00_O20 isochrone map shows that the study area was half graben basin during Rupelian time. This half graben inverted upwards forming positive flower structure due to late Oligocene compression in north northwest-south southeast direction (Chapter 3).
2) Based on different the attribute maps and images that have been created for individual reservoir packages, O15 depositional model shows eastern and western lobe complexes which might be fed by one or two feeding systems. Additionally, O18 depositional model displays amalgamated lobe complex at the western part of the area, part of lobe complex (may be) at the central part and channelized lobe complex at the eastern part of the study area which might be fed by one or more different systems. So, further seismic mapping should be made at the southern areas of the study area to know whether O15 and O18 reservoir packages were fed by one or more feeding systems. More wells need to be drilled especially at the eastern part of the study area to aid in architectural elements identification of O15 and O18 reservoir packages (Chapter 4).
3) Based on a log-log plot of width versus maximum thickness, the O15 and O18 reservoir packages lobe complexes could be deposited in confined systems (i.e., these lobe complexes have aspect ratio closer to ~ 1000:1) that agrees with core observations which had been interpreted as confined sheets (i.e., in this work called confined lobes). In contrast, the used models in architectural elements interpretation of O15 and O18 reservoir packages represent unconfined systems that in turn indicate the reservoir lobe complexes deposited in unconfined setting. So, further seismic mapping should be made in areas around the study area to better quantify the degree of confinement and investigate whether O15 and O18 reservoir packages were deposited in confined or unconfined systems (Chapter 4).
4) The O18 cored main sandbody a relatively thick heterogeneous but overwhelmingly sand dominated, ’coarse-grained sandbody’ dominated by massive sandstones that are locally cemented and fractured. Several granular sandstones and mudclast-charged muddy sandstones have also been identified. Massive, techtonized massive and techtonized massive granular sandstones are considered the main reservoir (good reservoir quality) lithotypes as they support moderate to good helium porosity and good to very good horizontal permeability while cemented, mud laminated, rippled laminated disrupted sandstone and mudclast charged muddy sandstone are considered non reservoir (bad reservoir quality) as they display poor helium porosity and very poor to poor horizontal permeability. The observations that have been made based on the cored main sandbody support the lobe interpretation where thin beds at the base of the core, bypass indicators and nearly horizontal erosive surfaces, the prevalence of amalgamation and ‘clasts’ in a series of crude fining upward have been identified. More analysis and observation should be made to identify the lobe elements of O18 lobe complex. There is no core has been captured from O15 interval. So, core should be acquired at O15 main sandbody in order to study O15 reservoir characteristics and rock quality (Chapter 5).
5) X2-well-OH displays serrated motif that could be interpreted as individual lobes that form the western O15 lobe complex. X1-well-OH, X2-well-OH and X2-well-ST1 log responses show blocky shape, bow shape, coarsening and fining upwards for O18 main sand units that could be interpreted as individual lobes that form the western area amalgamated lobe complex (Chapter 5).
6) All the three wells display good to excellent porosities, variable saturations and net pay thicknesses. Although these wells penetrated the top of 4-way dip closure, the determined net pay thicknesses for the three wells range between 0.5 and 11 m (uneconomic) for O15 sand units. So further work needs to be made to answer this mystery. Additionally, the absence of density log limits the porosity, saturation, net reservoir, and net pay calculations (Chapter 5).
7) O18 and O15 reservoir packages display different lobe complexes as X1-well-OH penetrated thicker, architecturally more complex, blocky and fossiliferous O18 sandy package than the sandy package penetrated by X2-well-OH. X1-well-OH displays two pluses of transported sediments separated by hemipelagic fines while X2-well-OH displays transported sediments only. O18 and O15 reservoir packages attribute maps show different seismic facies and different lobe complexes at X1-well-OH and X2-well-OH. O18 individual sand units penetrated by both wells exhibit different water saturations. O18 reservoir package at the X1-well-OH does not in pressure communication with the O18_reservoir package at the X2-well-OH (Chapter 5).