CONTRIBUTION OF SEQUENCE STRATICRAPHY IN THE HYDROCARBON MATURATION AND PRODUCTS OF SOME CRETACEOUS ROCK UNITS IN ABU GHARADIC BASIN, WESTERN DESERT, EGYPT
ABU-BAKER F. MAKY
Egyptian Petroleum research Institute (EPRI) |
Integration of wireline log data and lithologic characteristics are used to build-up the sequence stratigraphy of both Kharita and Bahariva formations in AG-4 well. Western Desert, Egypt. Kharita Formation is characterized by the presence of maximum flooding surface, as supported by the presence of glauconite underlain by a transgressive system tract and overlain by progradational parasequence sets. Moreover, the upper part of Kharita and Bahariya formations represent the start of aggradational phase, in which this interval was ended by the beginning of a retrogradational stage.
Composition of the dispersed sedimentary organic matter (SOM) shows the presence of three main groups. These include amorphous organic matter group, phytoclast group (composed of opaque equidimensional, opaque lath, wood with pits, wood without pits, resins, cuticles and fungal hyphae) and palynomorph group (spores, pollen grains and little dinofiagellate cysts). Thermal alteration index (TAl) of the studied kerogen is ranged between -2 and -3, that reflects marginal mature to mature organic matter. The cluster analysis of the sedimentary organic matter reveals the presence of two super palynofacies groups (A and B) associated with another group (C). The amorphous organic matter is the main component in the super cluster (A), where the phytoclast group represents the main constitution in the super cluster (B). Eventually, the palynomorph group is present in a waxing quantity of the cluster (C). Gas chromatography of the extracted bitumen and CPI values shows a gradual waning from base to top (10.7, 3, 1.1 and 0.61), indicating the waxing of the oil prone organic matter. These values indicate that the terrestrial materials are the major component of the SOM and are characterized by biodegradation. From the organic matter constituents and geochemical data, the probable hydrocarbon products are mainly gas with few oils.
From all the previous data and results, the environment of deposition is ranged between low to moderate energy fluviomarine to shallow marine environments, graded from oxidizing to highly reducing conditions under humid climate.
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