Publikationsserver der RWTH Aachen University
Geodynamic evolution and petroleum system of Abu Gharadig Basin, North Western Desert, Egypt
Abstract
dc:descriptionAbu Gharadig basin is a generally complex geological structure composed of pull-apart grabens. It was actively subsiding since the Paleozoic with a downwarp initiated since Carboniferous time and continued throughout the Jurassic and Cretaceous. The strongest downwarp was during the Maastrichtian when a thick Khoman section was deposited. To improve the understanding of the geodynamic evolution and the hydrocarbon potential of Abu Gharadig basin the aim of this work was to provide a better coverage of generation, migration, and accumulation of hydrocarbons and multivariable processes that occur during the long basin history by the application of Petroleum System Modeling. Applying basin modeling makes it possible to evaluate the four dimensional controls on source, reservoir and seal rock distribution, the master tectonic mechanisms, as well as source rock maturation, migration and trap formation. Petroleum potential therefore is influenced not only by the complex distribution of source, seal and reservoir rocks, but also by the effects of burial, uplift and erosion, which all undergo rapid variations in time and space. The integration of the well logging interpretation with the available geochemical data of the sedimentary units led to the construction of 1D and 2D basin models to evaluate the thermal history of the sedimentary sequence. With the results of the 1D basin modeling, a zone favorable for the generation of hydrocarbon from proposed source rocks was defined based on the deposition and the thickness of the overburden rocks and the timing of the generation and migration of the generated hydrocarbons. Additionally, 1D basin modeling was mainly applied for the estimation of the generated and expelled amounts of petroleum, while the reservoir characterization was done with a detailed interpretation of well logging data using software called “Interactive Petrophysics”. The evaluation of the results of vitrinite reflectance measurements for different wells in the basin was performed to obtain calibration data for 1D basin modeling. In this context, the influence of temperature on organic matter had to be evaluated. Maturity data also allowed calculating paleo-temperatures for the time of maximum burial or maximum temperatures. Thus, the amount of erosion was achieved. A heat flow history was assumed with high heat flows occurring during Late Jurassic-Early Cretaceous times in conjunction with the rifting taking place at this time. In all 1D models, the present-day heat flow is in accordance with temperature data and corrected bottom hole temperatures from wells investigated. Best accordance between measured and calculated present-day temperatures was achieved with present-day heat flows in the range of 43-49 mW/m2. Lowest present-day heat flow values were modeled for BED 3-3 well (due to rapid sedimentation or deep-seated basement) and highest values for well BED 2-1 well (the basement at shallower depth). The results of the 1D simulations show the differences in burial, thermal and maturity history for the principle tectonic events. Much of the oil generated by source rocks never reaches a reservoir. It remains disseminated throughout the source rock matrix, and is dispersed along secondary migration pathways. The small reserves are probably a reflection of limited trap volume as well as inefficient migration focusing. Small fields are presumably a result of post-charge tilting and spillage from once larger accumulations. The reservoirs based on well-calibrated 1D model experienced more than 80°C since Late Cretaceous time that retreated the biodegradation effect and suggests a thermodynamically stable crude oil without any possibility to secondary cracking gas generation. There is no indication of bacterial degradation, as shown in the n-alkane distribution diagram and the thermal history of the reservoir intervals. The timing and location of the generation and expulsion of hydrocarbons was directly controlled by the resulting thermal history, while the subsequent migration and accumulation of hydrocarbons and mineral-bearing fluids was significantly influenced by the structural history. Differences in hydrocarbon phase (oil and gas accumulation) productivity in Cretaceous-reservoired petroleum systems of the Abu Gharadig Basin appear to be related to migration and entrapment style and post-charge destructive processes. Across-fault seals often limit trapping effectiveness, because of higher-amplitude structures and greater fault displacements with more frequent across-fault juxtaposition of reservoir against younger sands. However, geochemical and burial history considerations indicate that the oil and gas trapped must be migrated from the deeper kitchen in the Abu Gharadig Basin or resourced from a pre-Cretaceous mature source rock. Therefore, the different hydrocarbon phase distribution in the area is explained as result of recent charge or migration due to seal efficiency and fault juxtaposition. In addition, multi fill and spill suggested as well. Normally, more than one interpretation fits the observable data, each with different implications for petroleum plays. Although every attempt was made to minimize errors, it is perhaps inevitable that errors were made and not detected. In this regard, if the reader should detect such errors, the researcher would be greatly indebted if these brought to his attention, so that they may be subsequently corrected. Similarly, any suggestion in the type and mode of coverage of the materials would be greatly appreciated for future research. Suggestions and comments from those who might use this research for that purpose are certainly welcomed
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2009
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Ahmed, Mohammed Awad Ahmed
- Contributors dc:contributor
-
- Littke, Ralf
Subjects
dc:subject × 5Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- eng