LEE- Jeoloji Mühendisliği Lisansüstü Programı
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ÖgeUnconventional hydrocarbon assessment of the Silurian Formation, Ghadames Basin, Northwestern Libya(Graduate School, 2024-12-20) Borovac, Emir ; İnan, Sedat ; 505191310 ; Geological EngineeringThe Silurian Tanezzuft Formation in the Ghadames Basin, Northwestern Libya, represents a critical focus of unconventional hydrocarbon exploration, leveraging its extensive organic-rich hot shales. This study undertakes a comprehensive geological, geochemical, and modeling analysis to elucidate the hydrocarbon potential of the Tanezzuft Formation. It integrates basin modeling with PetroMod software to evaluate burial histories, thermal maturity, and hydrocarbon generation, highlighting the formation's pivotal role in the region's petroleum system. Geologically, the Ghadames Basin spans across Northwestern Libya, Southern Tunisia, and Eastern Algeria, covering approximately 350,000 square kilometers. Structurally a passive continental margin, it exhibits a rich sequence of sedimentary deposits, with Paleozoic formations reaching up to 6,000 meters in thickness. Within this sequence, the Tanezzuft Formation emerges as a dual-functional unit, acting both as a source rock and an unconventional reservoir, with its basal hot shale being the primary focus. The stratigraphy reveals an intricate interplay of organic-rich shales and reservoir sandstones, further enhancing the region's hydrocarbon potential. The Tanezzuft Formation's hot shale intervals, deposited under anoxic marine conditions, are characterized by total organic carbon (TOC) values ranging from 1% to 18%, reaching up to 20% in some depocenters. The kerogen composition is predominantly Type-II, indicative of oil-prone organic matter, with significant thickness variations of up to 450 meters. This heterogeneity underscores its potential for oil and gas generation. The study dispels prior claims of Type-III kerogen presence, attributing such misinterpretations to the shale's graptolite content, which mimics Type-III characteristics. Basin modeling, a cornerstone of this research, provides critical insights into the thermal and burial history of the formation. For modeling, a 480 km long geolog'cal cross section, roughly in N-S orientation across the western Libya part of the Ghademes basin, was constructed based on available literature data. The model wa calibrated baed on present day subsurface temperature and thermal maturity data obtained on the Tanezzuft shales. After miodel was calibrated, the burial history, temperature history and hydrocarbon generation history have been evaluated. The striking future is that the first mjor burial took place prior toi Hercynian orogeny and at the depocenter, the Tanezzuft shale entered oil generation window. Uplift and erosion of the sedimentary cover led to shallowing of the Tanezzuft shales; leading to drop in temperature and frozen thermal maturity. The second burial episode took place between Triassic and Miocene leading to increasing maturity of the Tanezzuft shales and major oil and gas generation especially in the central basin. Second major uplift and erosion episode related to the Alpine orogeny commenced in the Miocene and continues at Present. This Alpine orogeny has shaped the Present-day burial and distribution of the Tanezzuft shale; shallower at the north and south parts of the basin and deeper and thus more mature in the central parts of the basin. The Tanezzuft shales exhibit maturity levels ranging between 0.6% and 2.0% Ro, with higher values correlating with increased depths toward the depocenter. Heat flow estimations and geothermal gradients corroborate the basin's suitability for hydrocarbon generation, with temperatures within the formation reaching 125-140°C, ideal for both oil and gas window maturation. Furthermore, the modeling highlights the onset of oil expulsion approximately 300 million years ago, with subsequent gas generation in deeper sections. The unconventional hydrocarbon potential of the Tanezzuft Formation is further emphasized through its mineralogical composition. The lower hot shale member demonstrates favorable brittleness, with quartz content exceeding 55%, making it amenable to hydraulic fracturing. This brittleness contrasts with the clay-rich warm shale, which is less conducive to production. Hydrocarbon generation and expulsion models reveal significant accumulations in sandstone intervals beneath the hot shales, with gas-to-oil ratios peaking in certain sections. Economic assessments estimate substantial in-place resources. The low-maturity oil in place is projected at 0.72 billion barrels, with peak maturity zones harboring approximately 14.7 billion barrels. Gas reserves are estimated at 67 trillion cubic feet at the highest maturity levels. Recovery factors ranging from 2% to 10% translate these estimates into potential yields of 0.3 to 1.48 billion barrels of oil and 1.34 to 6.7 trillion cubic feet of gas. In conclusion, this research underscores the Silurian Tanezzuft Formation's significance as a high-potential unconventional hydrocarbon resource in the Ghadames Basin. By integrating geological, geochemical, and advanced basin modeling techniques, it provides a robust framework for future exploration and development. The findings hold implications not only for regional energy strategies but also for advancing unconventional hydrocarbon methodologies globally.
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ÖgeUnconventional hydrocarbon resource assessment for the silurian shales in Diyarbakır Basin, Southeastern Türkiye(Graduate School, 2024-12-20) Sevimli, Ceren ; İnan, Sedat ; 505201335 ; Geological EngineeringThis thesis investigates the unconventional hydrocarbon generation potential of the Silurian-aged Dadaş shales in the Diyarbakır Basin, located in the Southeastern Anatolia Region of Turkiye. The Silurian-aged Dadaş Formation, like other Silurian shales in North Africa and the Middle East, presents significant potential for both conventional and unconventional hydrocarbon exploration. The Diyarbakır Basin remains relatively underexplored and offers untapped potential that requires further research. In the Paleozoic petroleum system, the Dadaş Formation has been identified as the source rock, while the Hazro and Bedinan sandstone formations have been identified as the reservoir rocks. This study focuses on the thermal maturity and hydrocarbon generation histories of the Silurian Dadaş shales, utilizing a basin modeling approach. In the Diyarbakır Basin, the Dadaş Formation reaches up to 400 meters in thickness, with an average thickness of 70 meters. The Dadaş Formation is divided into three members. The most organic-rich source rock is the lower member, Dadaş-I Formation. This formation covers an area of 12,000 km². The Dadaş-I Formation ranges in thickness from 200 meters and has an average thickness of 30-40 meters. According to geochemical analysis results from previous studies, the total organic carbon (TOC) content of the Dadaş shales is on average 5.9% by weight, though in some regions this value reaches up to 16.68% by weight, thus categorizing it as "hot shale." The kerogen type in the Dadaş hot shale is classified as Type-II, which is highly productive in terms of organic matter, indicating a high potential for oil generation. Additionally, the Hydrogen Index (HI) value ranges from 36 to 510 mg HC/g TOC with maturation. The pyrolysis Tmax values greater than 435°C in the Dadaş shales correspond to vitrinite reflectance values within the oil window. Given the global energy demand and the need for new resources, this research is crucial as it combines geological, geochemical, and basin modeling data to assess unconventional hydrocarbon potential. The basin model was calibrated using data from previous studies and created using PetroMod software (Schlumberger). The burial, temperature, thermal maturation, and hydrocarbon generation processes of the Dadaş hot shale were examined using 2D basin modeling techniques. The model was calibrated with data from four exploration wells in the region. The calibrated model results indicate that the Dadaş hot shales are within the oil generation window and that the main hydrocarbon generation occurred before the Alpine orogeny (uplift and erosion) phase. The modeling results provide insight into the burial history, maturity history, hydrocarbon generation history, and hydrocarbon content of the Silurian-aged Dadaş shales in the region. Calculations were made based on sample results from two wells over an 80 km-long geological section of the Silurian-aged Dadaş hot shale. The Dadaş hot shale has an average TOC content of 6% by weight and is characterized by significant amounts of oil, with minor amounts of gas. The pyrolysis Tmax values range from 434°C to 462°C, which correspond to vitrinite reflectance (%Ro) values ranging from 0.84 %Ro to 1.18 %Ro. These maturation levels play a significant role in the potential hydrocarbon generation of the shales. The surface temperature has been determined to be 20°C, with a geothermal gradient of 25°C per kilometer. According to the geological cross-section, the Dadaş hot shale has been buried deeper from south to north, leading to an increase in formation temperature ranging from 75°C to 120°C in the same direction. According to the modeling results, hydrocarbon generation is lower in the southern part of the Diyarbakır Basin and higher in the northern part. This is due to the deeper burial of rocks in the north and higher levels of maturity. Therefore, it has been determined that oil generation increases and the onset of oil formation occurs earlier from south to north. The modeling results indicate that the oil generation of the Dadaş hot shale started approximately 6 million years ago and reached its peak around 1 million years ago. According to the modeling, hydrocarbons generated in the Dadaş hot shales have migrated to reservoir rocks such as the Hazro and Bedinan sandstones. Maturity and oil-in-place (OIP) calculations were made based on the analysis of Dadaş hot shale samples from previous studies. The oil volume in the Dadaş hot shale is estimated to range between 11.6 and 84 billion barrels based on minimum and maximum maturity values. Considering that 2-10% of this oil can be produced using unconventional methods, the technically recoverable oil is estimated to range between 0.23 and 8.4 billion barrels. Thus, it has been concluded that the Dadaş hot shales contain a significant amount of economically recoverable oil. In unconventional methods, horizontal drilling and hydraulic fracturing are performed for hydrocarbon extraction from the source rock. Analyses of the Dadaş hot shales have shown that they are rich in clay. A potential disadvantage of this is that the clay-rich nature of the Dadaş shales may lead to technological challenges in hydraulic fracturing required for the extraction of this oil. To better understand the hydrocarbon potential of the region and evaluate the effectiveness of production methods, further field studies, drilling, and geochemical analyses are recommended.