M. Sh. El-Gayar

Application of gas chromatography with atomic emission detection to the geochemical investigation of polycyclic aromatic sulfur heterocycles in Egyptian crude oils

Twelve crude oils from a number of producing wells in the Gulf of Suez and Western Desert, Egypt were characterized by a variety of saturate biomarker compositions. The biomarker distribution clearly grouped the Gulf of Suez oils into two source-related types but revealed significant differences among the Western Desert oils. The oils were fractionated into saturates, mono- and polyaromatics; and the distribution of polycyclic aromatic sulfur heterocycles (PASH) in the polyaromatics fraction was investigated by gas chromatography (GC) with atomic emission detector (AED) in the carbon- and sulfur-selective modes. This makes possible the evaluation of the distribution patterns of PASHs even in cases where their relative abundance is low. The thiophenic distribution fingerprints were utilized for oil/oil correlations. Significant differences in the relative abundance of benzothiophenes and dibenzothiophenes were obvious between the Gulf of Suez and Western Desert oils. Moreover, the PASH pattern distinguished between oils derived from carbonate and siliciclastic source rocks. Maturity parameters based upon methyldibenzothiophene isomers were found consistent with other maturity-dependent saturate biomarkers.

Application of geochemical parameters for classification of crude oils from Egypt into source-related types

Abstract Seven crude oils representing the different petroleum-bearing basins in the Western Desert were characterized by a variety of biomarker and nonbiomarker parameters. For comparison, one crude oil from the Gulf of Suez region has also been studied. The oils have been analyzed for geochemical biomarkers using GC and GC-MS techniques. The results reveal significant differences within the oils that suggest five oil types. Type 1 oils from the Gulf of Suez show C 29 /C 30 17α(H) hopane ratio >1, high C 35 homohopane index, and the presence of considerable amounts of gammacerane indicating a marine saline carbonate or evaporite source rock and highly reducing (low Eh) conditions. Type 2 oils from Matruh basin and type 3 oils from Shushan basin are very similar and show relatively high Pr/Ph ratios, low sulfur and metal contents, paucity of C 30 steranes and the presence of high relative abundance of 17α(H) diahopane (C 30 *) suggesting that they probably originated from source rocks containing a significant proportion of higher plant material. Another related feature of these oils is the absence of 18α(H)-oleanane which suggests a source age older than Cretaceous. Type 4 oils from Abu-Elgharadig basin show terpane distribution dominated by C 24 tricyclic, absence of C 30 *-diahopane and medium diasterane/sterane ratios which reflect generation from marine siliciclastic source rocks. Type 5 oils from Alamein basin possess source biomarkers indicating a mixed contribution of terrestrial and marine sources. The presence of measurable amounts of oleanane in this type of oils suggests source rocks deposited in deltaic or near shore environment in Post-Cretaceous basin.

RELATIONSHIP BETWEEN PETROLEUM COMPOSITION AND DEPOSITIONAL ENVIRONMENT OF PETROLEUM SOURCE ROCKS FROM THE GULF OF SUEZ AND THE WESTERN DESERT OF EGYPT

ABSTRACT Crude oils from the Gulf of Suez and the North Western Desert of Egypt have been analyzed for geochemical biomarkers using GC and GC-MS techniques. The biomarker compositions of the crude oils have been used to differentiate crude oils of non-marine, normal marine and marine carbonate sources. The geochemical features of Zaafarana crude oil from the Gulf of Suez Basin indicate a marine carbonate depositional setting. One crude oil from Budran however, possesses geochemical characteristics consistent with an origin from source rock deposited in normal marine conditions. Bahar and Morgan show normal marine source rock deposition environment with terrigenous organic matter input. On the other hand, the crude oils from the North Western Desert have bulk and biomarker characteristics cosistent with non-marine depositional setting, with the exception of one oil sample which appears to have a mixed marine/terrestrial sources. The presence of oleanane in some of these oils suggests source rocks deposited...

MATURITY-DEPENDENT GEOCHEMICAL MARKERS OF CRUDE PETROLEUMS FROM EGYPT

ABSTRACT Maturity-dependent trends of a number of biomarker and nonbiomarker geochemical parameters were examined in crude oils from the Western Desert and the Gulf of Suez, Egypt. Molecular maturity assessments showed that all oils are at an advanced level of thermal maturity, and many ratios, such as CPI, hopane/hopane + moretane, C31 22S/22S + 22R hopanes and C29 ααα-20S/20S + 20R steranes were almost identical and have reached their thermal equilibrium values. Changes in the Ts/Tm and C29 ββ/(ββ + αα) steranes however, showed a more advanced level of thermal maturity for Umbaraka oil. On the other hand, correlations utilizing the nonbiomarkers API gravity, ΣV, Ni, sulfur content, sat/arom, and Ph/n-C18 ratios did show more distinct differences and are consistent between the oils.

Aromatic Steroids in Mideastern Crude Oils: Identification and Geochemical Application

Abstract The aromatic fractions of three crude oil samples from Iraq, Iran, and Saudi Arabia were isolated by using the method of silver ion-silica solid-phase extraction. Two series of aromatic steroids were recognized in these fractions using computerized gas chromatography-mass spectrometry corresponding to mono- and triaromatic steroids applying the mass chromatography at m/z 253 and m/z 231. The mass chromatogram traces show considerable differences that allow the use of the aromatic steroid distribution patterns as fingerprint for these oils. The oils contain significant amounts of mono- and triaromatic steroids having the C-24 ethylsteroid skeleton abundant in terrestrial sources. The abundance ratios of the short- to long-chain components of the mono- and triaromatic steroid hydrocarbons, together with the steroid aromatization parameter, indicate that the Iraqi and Saudi oils are at advanced maturity levels relative to the Iranian oil.

Utilization of GC/AED for Investigating the Effect of Maturity on the Distribution of Thiophenic Compounds in Egyptian Crude Oils

The polyaromatic compositions of 12 Egyptian crude oil samples from the Western Desert and Gulf of Suez regions were analyzed using gas chromatography in conjunction with sulfur-selective atomic emission detection. The results show the variation in distributions of benzothiophenes and dibenzothiophenes in oils with different maturity levels. The ratio of benzothiophenes to dibenzothiophenes has been applied successfully as tool to evaluate maturity changes where it correlates well with other maturity parameters. A cross-plot of benzothiophenes/dibenzothiophenes versus isoprenoid/n-alkane ratios consistently classified oils according to their maturity rank.

Utilization of Trace Metals and Sulfur Contents in Correlating Crude Oils and Petroleum Heavy Ends

Abstract The asphaltic components of four crude oils were analyzed for their V, Ni and Co contents. The metallic concentrations increased with increasing the molecular weight and the polarity of the fraction and the highest concentration is associated with asphaltene fraction. The V, Ni and Co might have been incorporated during the genesis of the parent crudes as the V/Ni, V/Co and Ni/Co markers are fairly uniform in the asphaltenes and unfractionated asphalts. In addition, the total V and Ni together with S were measured in twelve crude oils from different geographic locations and geologic ages. The Ni/S marker can be considered as characteristic marker for all the crudes studied. On the other hand, V/S marker is too precise in correlating with the geologic age of the oil and is decreasing by maturation.

Application of petroleum markers to geochemical and environmental investigations

Abstract Application of trace-metal and biological markers to geochemical studies has shown that crude oils could be correlated or differentiated according to their geologic age. The V/Ni, V/Σ Ni, ...

DISTRIBUTION OF BIOMARKERS IN HIGHLY WEATHERED PETROLEUM RESIDUE FROM MEDITERRANEAN WATERS

ABSTRACT The aliphatic and aromatic fractions of a beach tar sample from the Mediterranean coast of Sidi Kreir, 37Km west of the city of Alexandria was analyzed by GC and GC/MS techniques. A complete analysis was carried out to investigate chemical composition changes, fate of weathered oil residue and possible source identification. The distribution of sterane, hopane, mono-and triaromatic steroids, C2 - and C3 - phenanthrenes and dibenzothiophenes and chrysenes, however, had remained unaltered by weathering. The beach tar possessed geochemical features consistent with a marine carbonate or evaporite source depositional environment under normal saline, reducing conditions. The GC fingerprints pointed to heavy fuel oil as a possible source for the tar sample.

OCCURRENCE AND DISTRIBUTION OF BICYCUC AND TRICYCLIC AROMATIC HYDROCARBONS IN CRUDE OILS FROM THE GULF OF SUEZ, EGYPT

ABSTRACT The distribution patterns of methylhomologs of naphthalene and phenanthrene in five crude oils from the southern part of the Gulf of Suez, Egypt, have been examined by quantitative capillary gas chromatography (GC) and computerized gas chromatography/mass spectrometry (GC/MS). In general, the relative abundance of individual naphthalenes and phenanthrenes were not significantly different in the five oil samples. Correlation between the source rock deposition and the abundance of specific methylnaphthalene and melhylphenanthrene isomers are consistent with a marine type source materials for the analyzed Gulf of Suez oils. Maturity parameters based on methylnaphthalene and methylphenanthrene isomers were almost identical and are consistent with an advanced stage of maturity. Further, calculated vitrinite reflectance (Re) confirmed that the sediments have a range of maturity within the “oil window”.