الفهرس 
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Abstract
The Abu-El Gharadig basin is a deep E-W trending asymmetric graben. It has dimensions of 300 km E-W and 60 km N-S, with an area of about 17500 km2, and basement at depths over 10 km. Its structure has been recognized as a major rift basin in which there are numerous localized highs in NE-SW oriented plunging anticlines that are believed to be fault-controlled folding. All studied wells (Spyglass-1X, AG-24, AG-29 and AG-31) are located at Khalda Petroleum Company (KPC) concession WD-30 which existed at the southeast of the Abu-El Gharadig basin.
There are five cycles that compose the stratigraphic section of alternating deposition between clastics and carbonate rocks. 1) Clastics sedimentation prevails the oldest sedimentary rocks including Paleozoic and Lower Jurassic formations. 2) Upper and Middle Jurassic rocks are composed of carbonates. 3) Lower Cretaceous up to Early Cenomanian contains mainly clastics cycle. 4) Carbonate Rocks are again deposited over northern Western Desert from Upper Cenomanian and to the Middle Eocene. 5) The upper clastic cycle includes the Upper Eocene– Oligocene, Miocene and younger section.
Materials and methods that used for the study are the backbone, so GUPCO and Khalda Oil Companies sent the ditch samples from wells (AG-24, AG-29 and AG-31) to be analyzed by EXLOG Services and the well Spyglass-1X to StratoChem Services Company to determine the TOC, Rock-Eval pyrolysis and %R0 analysis. Also, the well logs data (composite, gamma-ray, density, neutron, induction laterolog deep (ILD), photoelectric Effect (PEE) and sonic logs) are used in this study to aid in the construction of the burial history models of the studied formations. In addition to the above data, 20 2D seismic lines, passing through the above wells are used to determine the tectonic setting and the trapping of the oil and gas in the study area. These data are received from Khalda Petroleum Company after permission of the Egyptian Ministry of Petroleum.
The Rock-Eval pyrolysis data are responsible for determining the quantity, type and thermal maturity of the organic matter. The pyrolysis is a widely used degradation technique that depends on breaking a complex substance into fragments by heating it under an inert atmosphere. The Rock-Eval is expressed in mg/g of rock including four basic parameters (S1, S2, S3 and Tmax).
Generally, the %Ro values between 0.5 and 1.3% lead to the consideration that samples are within the oil generation window, while samples with values below 0.5% are considered thermally immature. Vitrinite reflectance of those greater than 1.3% indicates gas window maturity.
The relationship between TOC and depth of Spyglass-1X well reflects that Abu Roash (E) Member is a good source rock that ranged from 1.24 to 1.27 wt.%, while Abu Roash (F and G) members are ranging from good to very good source rock with TOC ranged from 1.2 to 2.45 wt.%. For the Rock-Eval pyrolysis data such as S1 and S2, the studied source rock ranges from fair to very good. The high values of TOC, S1 and S2 show that the Abu Roash (F) Member is the main source rock of the study area with mainly oil-prone kerogen.
In AG-24 well, the relationship between TOC and depth reflects that Abu Roash (F) Member is a good source rock with TOC 1.15 wt.%. The relationship between (S1 and S2) and depth revealed that the Abu Roash (F) Member is a fair source rock. While Abu Roash (G) Member is mainly poor to very good source rock, with TOC from 0.4 to 2.28 wt.%. The relationship between (S1 and S2) and depth showed that this rock unit is mainly poor but shows good to very good in one sample. Whereas Bahariya Formation is poor to fair ranges from 0.42 to 0.95 wt.% TOC and the S1and S2 data reflect mainly a poor source rock.
In AG-31 well, the relationship between TOC and depth showed that Abu Roash (A) Member is poor to good source rock having maximum value of TOC 1.05 and minimum value 0.4 wt.%. The relationship between (S1 and S2) and depth show poor to good source rock, while Abu Roash (E, F and G) members and Bahariya Formation are ranging from poor to fair source rocks with TOC from 0.4 to 0.61 wt.%, while the S1 and S2 data show a poor source rock.
In AG-29 well, the relationship between TOC and depth reflected that the Abu Roash (A, E and G) members, Baharyia and Kharita formations are ranging from poor to good source rocks with TOC from 0.4 to 1.25 wt.%, but Abu Roash (F) Member reached very good category with TOC ranges from 1.17 to 2.57 wt.%. On the other side, the S1 and S2 data showed that these rock units are ranging from poor to fair source rocks but, Abu Roash (F) Member ranged from good to very good source rock as reflected from TOC, S1 and S2 data.
The relationship between HI and OI of Spyglass-1X well reflects that the Abu Roash (E, F and G) members are represented by oil and gas-prone of mixed Type II/III Kerogen. The QI shows that, the organic matter of Abu Roash (E) Member is represented by gas-prone type, whereas the organic matter of Abu Roash (F and G) members is represented by oil and gas-prone type. The relationship between Tmax and HI indicates the percentage of type II, which reached 35% in Abu Roash (E) Member and 85% in Abu Roash (F and G) members.
In AG-24 well, the relationship between HI and OI reflects that, the Abu Roash (F and G) members and Bahariya Formation are represented by oil and gas-prone of mixed Type II/III Kerogen. The QI shows that the organic matter of Abu Roash (F) Member is represented by oil-prone type, whereas the organic matter of Abu Roash (G) member and Bahariya Formation are mainly oil-prone type. The relationship between Tmax and HI indicates that, the percentage of type II of mixed type II/III Kerogen, which reached 42% in Abu Roash (F) Member, 20% in Abu Roash (G) Member and Bahariya Formation.
In AG-31 well, the relationship between HI and OI reflects that, The Abu Roash (A, E, F and G) members and Bahariya Formation are mixed oil and gas-prone of type II/III and type III Kerogen. The QI shows that, the organic matter of these formations is represented by oil-gas prone type. The relationship between Tmax and HI indicates the percentage of type II of mixed type II/III Kerogen, that reached 68% in Abu Roash (A) Member, 20% in Abu Roash (E) Member, 10% Abu Roash (F) Member, 15% in Abu Roash (G) Member and less than 10 - 15% in Baharyia Formation.
In AG-29 well the relationship between HI, OI and the QI reflected that the Abu Roash (A, E, F and G) members, Bahariya and Kharita formations are represented by oil and gas-prone of mixed type II/III and type III Kerogen. The relationship between Tmax and HI indicates the percentage of type II of mixed type II/III Kerogen, which reached 43% in Abu Roash (A) Member and 59% in Abu Roash (E) Member, 79% in Abu Roash (F) Member, 25% in Abu Roash (G) Member, 30% in Bahariya Formation and 15% in Kharita Formation.
The %R0 data of the studied wells (Spyglass-1X, AG-24, AG-31 and AG-29) shows that, Abu Roash (A) Member of AG-31 well is representing the immature stage ranging from 0.4 to 0.49 %Ro, the early mature stage is represented by Abu Roash (E, F and G) members of Spyglass-1X well and Abu Roash (A, E and F) members of AG-29 well which ranging from 0.5 to 0.69 and the peak of generation stage is represented by Bahariya Formation of AG-24 well, Abu Roash (E and G) members and Bahariya Formation of AG-31 well and Abu Roash (G) Member, Bahariya and Kharita formations of AG-29 ranging from 0.68 to 0.81 %Ro.
Tmax values of the studied wells reflected that, Abu Roash (E, F and G) members of Spyglass-1X are existing on the margin of maturation stage, but Abu Roash (A, E, F and G) members, Bahariya and Kharita formations of the other studied wells reached mature stage. Whereas, the relation between depth and PI of Spyglass-1X well showed that Abu Roash (E, F and G) members existed at immature stage, while all Abu Roash (A, E, F and G) members, Bahariya and Kharita formations of AG-24, AG-31 and AG-29 wells are at the mature stage.
The relationship between (S1+S2) versus TOC in Spyglass-1X well shows that Abu Roash (E) Member falls in fair source rock in the generation potential, Abu Roash (F) Member ranging from fair to very good source rock and Abu Roash (G) Member exists in good to very good generation potential. In AG-24 well, Abu Roash (F) Member falls in fair generation potential category. The Abu Roash (G) Member and Bahariya Formation are mainly poor generation potential. In AG-31 well, Abu Roash (A) Member is ranging from poor to good, while Abu Roash (E, F and G) members and Bahariya Formation are existing in poor generation potential. In AG-29 well Abu Roash (A and E) members are ranging from poor to fair generation potential, Abu Roash (F) Member from good to very good generation potential, but Bahariya and Kharita formations are poor generation potential.
The burial history model of Spyglass-1X well shows the depth (m) versus time (Ma) and the maturity EASY%Ro which reflect that, Abu Roash (F and G) members, Bahariya and Kharita formations are at early mature stage 0.5 - 0.7%Ro. The formation temperature increases with depth and burial that reached 104.5oC at the bottom 3657.6 m a good correlation between EASY%Ro and measured %Ro that gives the model more accuracy and reality.
The burial history model of AG-24 well represents that, Abu Roash (A, B, C, D, E, F and G) members are at early mature stage of 0.5 - 0.7 %Ro and the lower part of Bahariya Formation at mid mature stage 0.7 - 1 %Ro. The formation temperature reaches 87.6oC at the bottom 3611.5 m also shows comparison between EASY%Ro and measured %Ro and Tmax showing reliable results.
The burial history model of AG-31 well represents that the lower part of Khoman Formation and Abu Roash (A, B, C, and D) members are at early mature stage 0.5 - 0.7 %Ro, while Abu Roash (E, F and G) members and Bahariya Formation are at mid mature stage of 0.7 - 1 %Ro. The formation temperature reaches 118.3oC at the bottom 3646.9 m showing a good correlation between EASY%Ro and measured %Ro and Tmax.
The burial history model of AG-29 well represents lower part of Khoman Formation Abu Roash (A, B, C, D, E and F) members at early mature stage 0.5 - 0.7 %Ro and Abu Roash (G) Member and Bahariya and Kharita formations at mid mature stage 0.7 – 1%Ro. The formation temperature reaches 121.1oC at the bottom 3800.8 m, showing good matching between measured and calculated %Ro.
The timing of hydrocarbon generation for the studied wells can be summarized as the studied formations entered the onset of hydrocarbon generation during the Late Cretaceous period (from 75.89 to 66.47my) and reached the peak of hydrocarbon generation during the Neogene period from 19.05 to 3.75my. In Spyglass-1x well, the onset of hydrocarbon generation began from 75.89my at Kharita Formation but did not reach the peak of generation. In AG-24 well, the onset of hydrocarbon generation began from 68.69my and reached the peak from 3.75my at Baharyia Formation. In AG-31 well, the onset of hydrocarbon generation started from 66.47my and reached the peak from 12.76my at Baharyia Formation. In AG-29 well, the onset of hydrocarbon generation occurred from 67.78my and reached the peak from 19.05my at Kharita Formation.
In this work, the Petrel software is used to draw and interpret the seismic lines that passing close to the studied wells reflected that, the major trapping styles of the generated hydrocarbons of the effective source rocks are structurally of faulting and folding traps. Anticline folds are the most famous hydrocarbon traps in the study area. Also, the interpretation of these seismic data led to discover a new anticline prospective trap of AG-24 well.
6.2. Conclusions
from the study of source rock and basin modeling of some Cretaceous rock units in the Abu-El Gharadig basin, Khalda Concession, we can conclude that:
• The Abu Roash (F) Member has very good hydrocarbon potentiality and considered the main source rock of the area, while Bahariya and Kharita formations have poor to fair potentiality based on Rock-Eval pyrolysis and TOC analytical data.
• The values of HI and QI reflect that the kerogen is mainly Type II (Abu Roash members (A, E and F)( of marine origin with mainly oil-prone, Mixed Type II/III (Abu Roash G Member) of marine and terrestrial origin with mixed oil and gas-prone and Type III (Bahariya and Kharita formations) of mainly terrestrial origin with mainly gas-prone.
• The maturity parameters (%Ro and Tmax), and 1D burial history models of the studied wells reflected that the early maturation stage begun at Upper Cretaceous period from 65my to 77.5my, while the peak of hydrocarbon generation stage begun at Miocene period from 3.75my to 18.5my.
• The interpretation of 2D seismic lines reveals that the entrapment styles of generated hydrocarbons are mainly structural traps of normal faults forming horst and graben structures, and anticline folds which were charged with the generated hydrocarbons from the studied Cretaceous source rocks.
• Finally, to achieve good results and more accurate output the burial history models the modeled %Ro should be calibrated and integrated with measured Tmax and the measured %Ro values.