Тип бассейна: Платформ
Подтип бассейна: Пассивных окраин (перикратонно-океанический)
Класс бассейна: Периокеанический
Возраст бассейна:
Тип полезных ископаемых:
Геологический возраст начало:
Геологический возраст конец:
Площадь: 147641.55 км²
Nile Delta Basin
The Nile Delta Basin (NDB) is considered a major gas province where numerous trillions of cubic feet of gas have been discovered in the last ffty years in various stratigraphic layers from Oligocene to Quaternary (e.g., Sarhan 2021a, b, c; Sarhan and Safa 2017; El-Fawal et al. 2016; Abu El-Ella 1990; Abdel Aal et al. 2000). Many of the gas detections in the NDB are biogenic. However, there is also a thermogenic source as evidenced by some oil discoveries, especially in the pre-Pliocene (Esestime et al. 2016). The NDB has a gas reserve of roughly 223 trillion cubic feet spread across over 126 gas felds in the cone of NDB (Kirschbaum et al. 2010). In addition to the existence of a considerable biogenic gas component, these felds are assumed to be generated predominantly from mature source rocks equivalent to the Neogene sediments (Vandré et al. 2007).
Since 1963, the Abu Madi Fm. has been the main source of gas in the ofshore and onshore areas of the NDB (e.g., Sarhan 2021a; Abu El-Ella 1990). However, in 2000, British Gas and BP corporations discovered the Sienna, Sapphire, Simian, and Taurus plays in the western ofshore sections of the NDB, focusing their exploration eforts in these areas. All these plays are part of a Pliocene slope-turbidite (Abdel Aziz and Shann 2005).
The exploration process in the NDB in the 1990s was focused on ultra-deep water from Pliocene turbidite (such as the Ha'py Field). The Lower Miocene-Oligocene sands have yielded recent produced positive results in the NDB, such as, the Raven feld (Esestime et al. 2016).
ENI Company drilled a new play in 2015 at a depth of 1500 m near the Egypt/Cyprus border. This play depicts a massive carbonate platform from the Early-Middle Miocene epoch that rests behind a thick layer of Messinian evaporates. Such play was drilled by Zohr-1 Well. This discovery has a total thickness of 628 m with 430 m net pay. The gas volume present is estimated at 30 TCF (Esestime et al. 2016).
The sandstones of the Kafr El-Sheikh Fm. (Early-Middle Pliocene) as well as the El-Wastani Fm. (Late Pliocene) are the most promising opportunities for gas exploration in the Nile Delta's ofshore areas (e.g., Othman et al. 2018; Lashin and Mogren 2012; Leila and Mohamed 2020). In general, there are no difculties in exploring new plays in the Pliocene section of the NDB. However, the high pressure, poor-seismic imaging, and lack of direct hydrocarbon markers are all problems that exist in the pre-Messinian sequence (Dolson et al. 2002). One of the main hydrocarbons plays is the Pliocene sediments in the NDB, which show outboard progradation with time. It has turbidites in the shape of channels, channel levees as well as sheet sands on the slope and basin foor (Abdel Aal et al. 2000). Over the entire rotational fault block, the principal axis of the Pliocene deposition trends SE-NW. Large saltinduced faults cut several underground channels, making them interesting exploration opportunities (Abdel Aal et al. 2000). Successful exploration wells represent the Pliocene channel plays in the ofshore NDB such as; Osiris, Seth, Rosetta, Ha'py, Seti, Scarab and Safron felds (Abdel Aal et al. 2000). The Pliocene slope-turbidite plays (such as; Sienna, Sapphire, Simian and Taurus) are recent discoveries in the western ofshore NDB (Abdel Aziz and Shann 2005).
The shallow Pliocene gas reservoirs in the NDB are characterized by visible direct hydrocarbon indicators (bright and flat spots) on seismic profiles, increasing the success rate to about 90% (Dolson et al. 2005; Samuel et al. 2003). Several bright spots inside the Pliocene–Quaternary strata that overlies the Messinian evaporites, which have been drilled with verified gas discoveries in the North Sinai Concession (Ewida and Darwesh 2010). The offshore part of Sinai has favourable hydrocarbon accumulation characteristics and requires more intense investigation (Abd-Allah et al. 2020). Furthermore, the Pliocene–Pleistocene succession of the TAO Field remains intriguing for holding shallow gas reservoirs near to multiple hydrocarbon discoveries that warrants NOSPCO's extra exploration (Ewida and Darwesh 2010). This assessment improves the quality of the gas reservoir and identifies additional economic natural gas reserves in the North Sinai Concession, which is located off the coast of the NDB.
The Baltim Field is the northern continuation of the Abu Madi paleo-valley. It is 500 km2 in size (about 25 km long and 19 km wide) at the offshore section of the NDB and located approximately 25 km from the Egyptian coast between 31.62° and 31.94°N and 31.02° and 31.44°E (Fig. 1).
Fig. 1 A Regional map represents the location of Baltim Field within Abu Madi Paleo-Valley plus the positions of diferent gas felds in the ofshore sector of the Nile Delta Basin (modifed after Sarhan and Collier 2018; Bosworth et al. 2008). B Map displays the available seismic data and the sites of the inspected wells in Baltim Field
The objective of the present work was to appraise the reservoir quality of the Abu Madi sandstones in Baltim gas-field in the northern part of Egypt’s NDB. This goal achieved by performing the petrophysical evaluation to delineate gas-bearing intervals in five examined wells penetrating the Abu Madi Fm.; Baltim East-2, Baltim East-3, Baltim East-5, Baltim North-1 and Baltim North-2 (also known as the BE-2, BE-3, BE-5, BN-1 and BN-2, respectively). All five wells are inside the Abu Madi paleo-valley at the northern portion of the basin (Fig. 1). The construction of 3D seismic attributes as well as 3D reservoir model, that integrates the geological, geophysical and production data of the hydrocarbon reservoir (e.g., Ashraf et al. 2019; Vo Thanh et al. 2019, 2020) in the Baltim Field has not been performed in the current research. This is because the accessible data in this study does not include; 3D seismic survey, core data or a large number of drilled wells. All of these additional data are required to build a reservoir model with high accuracy and low uncertainty (e.g., Vo Thanh and Sugai 2021).
Geologic setting
The NDB is a passive-margin sedimentary basin covering a>250,000-km2 area in the eastern Mediterranean area (Sestini 1989). It was formed by subsidence, and the subsequent tectonic extension that detached the African–Arabian plate from the Eurasian plate during Upper Triassic–Lower Cretaceous time (Dolson et al. 2001; May 1991). Harms et al. (1990) referred to the southern margin of this east–west rift as the Hinge Zone. The NE–SW normal faults (Rosetta trend) afected the Nile Delta's northwestern part. However, the northeastern part is controlled by NW–SE-striking faults (Bardawil trend) (Fig. 1).
The subsurface Oligocene–Quaternary section of the NDB is ~ 6.0 km in thickness (Hussein and Abd-Allah 2001). The Neogene sediments in the NDB were deposited in sequential regression–transgression cycles under marginal- to open-marine settings (Hashem et al. 2010). This Neogene section is a siliciclastic sequence including (from base to top) the Sidi Salim, Qawasim, Abu Madi, Rosetta, Kafr El-Shiekh, El-Wastani and Mit-Ghamr Fms. (Fig. 2).
Fig. 2 Mesozoic–Cenozoic lithostratigraphy of NDB, after Egyptian General Petroleum Corporation (1994)
The Abu Madi Fm. consists mainly of intercalated sandstone and shale (Rizzini et al. 1976) formed throughout the Upper Miocene Epoch (El Heiny and Morsi 1992; EGPC 1994) in the fnal stage of the Messinian syn-rift megasequence, that infuenced the subsurface sedimentary section in the NDB (Sarhan et al. 2014; Sarhan 2022). The depositional evolution of the Abu Madi Fm. was intensely infuenced by tectonic rather than sea-level changes (Sarhan 2015). The Abu Madi paleo-valley encompasses proto-Nile distributaries that incised a wide fuvial or canyon system (Fig. 1). This cutting through the preexisting continental shelf of the Mediterranean Sea was related to the signifcant drop in the global sea in Messinian time (Barber 1981; Harms et al. 1990; Sestini 1989), which resulted in the deposition of the Rosetta Formation, a dense body of evaporites covering the eastern Mediterranean, and the deposition of the Abu Madi Fm. as incised-valley fll. This inflling started as fuvial facies (lowstand systems tracts) followed by estuarine facies (transgressive systems tracts) (Salem et al. 2005).
Composite Petroleum System and Assessment Units
The Mesozoic-Cenozoic Composite Petroleum System was defined to include the possibility of viable source rocks of Jurassic, Cretaceous, Oligocene, Miocene, Pliocene, and Pleistocene ages (Abdel Aal and others, 2000, 2001; Dolson and others, 2001a, b; Vandre and others, 2007). Four assessment units (AU) were defined geologically within the composite petroleum system. Two of the assessment units—Eratosthenes Seamount AU and Mediterranean Ridge AU—were defined northward of the Nile Cone but were not quantitatively assessed. The two assessed areas are the Nile Cone AU and Nile Margin Reservoirs AU (figs. 3 and 4).
Fig. 3. Location of four assessment units in the Nile Delta Basin Province in the eastern Mediterranean. (Map not definitive for political boundaries.)
Oil and gas were generated from multiple Mesozoic and Cenozoic sources including: (1) hypothesized Jurassic marine and terrigenous shale; (2) Cretaceous argillaceous shales and limestones; (3) Oligocene and Miocene terrigenous source rocks; and (4) possibly biogenic sources (Vandre and others, 2007). Source rocks are thermally mature in deeper parts of the province (Abu El-Ella, 1990; Shaaban and others 2006). Petroleum charge is confirmed by more than 100 producing fields, numerous oil seeps, mud volcanoes, and gas chimneys imaged on seismic profiles (Loncke and others, 2004). Reservoirs are Mesozoic to Paleogene carbonate and clastic reservoirs and Neogene-Quaternary deltaic, nearshore marine, deep-water slope channel, and sheet and fan sandstones (Cross and others, 2009; Samuel and others, 2003) and Messinian-age (latest Miocene) incised-valley-fill deposits (Dolson and others, 2001a). Traps are structural and stratigraphic with numerous modifications because of inversion, salt removal, normal faults, growth faults, and mass transport (Loncke and others, 2006). Migration was enhanced by major intersecting fault systems. Lithologic and diagenetic seals were effective in creating pressure compartments (Nashaat, 1998).
Fig. 4. Schematic geologic cross section of the Nile Delta Basin Province illustrating the geologic definition of three of the four assessment units (AU) in this study (dotted red lines): Nile Margin Reservoir AU, Nile Cone AU, and Eratosthenes Seamount AU. The fourth AU, Mediterranean Ridge, is out of the plane of the cross section. Modified from Barber (1981) and Abdel Aal and others (2000). Location of projected section shown in figure 1. 1, Miocene (post-Messinian) and Pliocene-Quaternary; 2, Messinian Salt; 3, Miocene (pre-Messinian); 4, Paleogene-Cretaceous; 5, hypothesized pre-Cretaceous; 6, Eratosthenes Seamount.
The Nile Margin Reservoirs AU is assumed to be sourced from deeper thermally mature source rocks, but currently only one oil field of minimum size is present in the AU. The Nile Cone AU is thought to be sourced mainly from thermally mature Neogene deltaic source rocks, but also there might be a significant biogenic gas component (Vandre and others, 2007). The Nile Cone AU contains two oil fields and 126 gas fields.
The geologic model used in the assessment of the Nile Delta Basin was derived from comparison of geologic analogs, oil and gas production data, proved reserves, and potential oil and gas resources for the maturely explored Niger Delta Province (Brownfield and others, 2010). The USGS used a minimum undiscovered field size of 5 million barrels of oil equivalent (MMBOE).
Data source: The potential of ofshore Nile Delta Basin natural gas reserves: a case study of Messinian reservoir in Baltim feld, Mohammad Abdelfattah Sarhan. 2022
Assessment of Undiscovered Oil and Gas Resources of the Nile Delta Basin Province, Eastern Mediterranean. U.S. Geological Survey (USGS). 2010
Следующий Бассейн: Pelagian