**8. Previous studies in Egypt**

#### **8.1 Egyptian Western Desert**

The Western Desert covers about 700,000 square kilometers (equivalent in size to Texas) and accounts for about two-thirds of Egypt's land area. This immense desert to the west of the Nile spans the area from the Mediterranean Sea south to the Sudanese border. The chemical fingerprinting of oils in this area is a great interesting research area for many proposes as for example identifying the sources of petroleum oil or complex environmental pollutants. The original sources of complex mixtures can often be identified by the relative abundance of some major individual compounds (e.g n-alkanes) forming a chemical pattern by ratios of specific constituents or by identifying source-specific compounds or markers (e.g triterpanes) in the environmental sample being investigated (Peters et al., 2005). These parameters depend mostly on the preburial environments of the living organisms, the depositional environments of the organic matter and the diagenetic processes in the source rocks.

In their work, Roushdy et al. (2011) utilize biomarkers characteristics together with bulk geochemical parameters to identify and characterize the crude oils and to assess the respective depositional environments and maturation. Variation of crude oil-gravities in the Western Desert reflects different stages of oil migration and accumulation as well as different oil source rocks in the same and different ages (Zein El Din et al., 1990).The authors attempt to assess the correlation between the crude oil samples and the potential source rocks to confirm the indigenous sources for the petroleum generation of some oilfields of the North Western Desert. This target was made throughout the study in detail of the analytical results for three crude oil samples collected from three oilfields in the North Western Desert oilfields (Meleiha, Misaada and Qarun) as well as three extract samples (Baharia, Kharita and Khtataba) from formations ranging in age from Upper Cretaceous to Middle Jurassic.

Biomarkers 179

The high concentrations of C27 - C29 diasteranes in case of Meleiha oil indicate input of marine organic source with more contribution from terrestrial organics (Waples and Machihara, 1992). The high diasteranes concentration compared to regular steranes suggest a clay rich source rock because the clay is required to catalyze the steroids transformation to diasteranes (Peters and Moldowan, 1991). Misaada and Qarun oils are characterized by slightly lower predominance of C27 steranes and higher abundance of C28 and C29 steranes indicating inputs from marine organic sources (Waples and Machihara, 1992). Moreover, the distributions of regular steranes C29, C27 and C28 on the ternary diagram reveal also more contribution from marine organic sources. The diasteranes concentrations compared to

The crude oil samples of Qarun and Misaada oilfields have Pr/*n*-C17 and ph/*n*-C18 ratios 0.28, 0.47 and 0.1, 0.1, respectively reflecting mostly mature and originated mainly from marine organic sources deposited under reducing environment. The crude oil of Meleiha oilfield has Pr/*n*-C17 and ph/*n*-C18 of 0.40 and 0.28 indicating mixed organic sources.

Terpanes biomarkers distributions derived from the m/z 191 mass chromatograms show that the C21-C25 tricyclic terpanes of Meliha oil appear to be the largest components which may support that the oil of Meleiha oilfield is more mature and sourced mainly from marine carbonate source rocks. At the same time, the C23, C24 and C25 tricyclic terpanes are generally of lower values compared with C22 indicating that the oil has some inputs from terrestrial organic materials (Hunt, 1996). The unusual low amounts of C30 extended hopanes seem to be associated with mixed organic sources (Moldowan et al., 1985). This

On the other hand, The C30 hopanes are the largest components in the series C27-C34 in oil samples from Misaada and Qarun oilfields. This indicates that the organic materials in these oils were originated mainly from saline and hypersaline environments (Peters and Moldowan, 1993). The extended hopanes are available as paleo environmental indicator (Waples and Machihara, 1992). The unusual large amounts of C30 hopanes seem to be

Bisnorhopanes are types of pentacyclic triterpanes present in significant concentrations in oil. Bisnorhopanes are observed in Guatemalan evaporites and frequency reported in other biogenic siliceous rocks of the circum-Pacific region (Connan et al., 1986). It is believed that sediments containing large amounts of bisnorhopane were deposited under anoxic conditions (Mello et al., 1988). The crude oils of Misaada oil field have relatively higher amounts of C28

Carbon preference index (CPI) values of the studied crude oils are close to unity, ranging

Pr/Ph ratio of the oil sample from Meleiha oilfield is 3.0 indicating oxidizing depositional environment of the crude oil while the crude oils from Qarun and Misaada oil fields have Pr/Ph ratios of 0.63 and 2.00 respectively reflecting that these crude oils were deposited under transitional (reducing– oxidizing) environments. These results indicate good correlation between crude oils from Qarun and Misaada oilfields with slight correlation to

Oil: source correlation reflect a good correlation between the extract samples of Kharita and Khatatba source rocks and crude oils from Meleiha and Qarun oilfields. The extract of

phenomenon can be displayed by the low ratio of C29/C30 extended hopanes.

bisnorhopane indicating more anoxic environment than Qarun and Meleiha oils.

regular steranes is low, suggesting a clay rich source rock.

associated with marine sources (Moldowan et al., 1985).

from (0.94 to1.04) indicating mature crude oils.

crude oil from Meleiha oilfield.

Fig. 7. Map of Egypt showing the main oil and gas fields.

The specific geochemical parameters have been assessed by the aid of gas chromatography and gas chromatographic-mass spectrometric analyses of the saturated fractions. The degree of the correlation between crude oils and the extracted samples was determined by studying the correlation scores for both oils and extracts. Eight correlation parameters have been studied for this purpose includes: saturates%, saturates/aromatics ratio, Cmax, C21+C22/C28+C29, CPI, pristane/phytane, pristane/*n*-C17 and pristane+*n*-C17/phytane+*n*-C18. An overall correlation score was obtained for each oil and extract by summing up the contribution from each parameter. The GC/FID chromatogram of the Meleiha crude oil sample is characterized by a monotonically decreasing homologous series of heavy normal alkanes (*n*-C25 to *n*-C30) and display odd carbon preference at *n*-C15 which reflects mature oils originated mainly from non-marine origin mainly terrestrial organic matters deposited under slightly oxidizing environment and slightly mixed with inputs from marine source (Hunt, 1996). The mode of distribution of *n*-paraffins in the crude oils of Misaada and Qarun oilfields show that the maximum abundance is at *n*- C15 to *n*-C25 reflecting marine origin.

The steranes distribution of crude oils was studied. Meleiha crude oil was found to be characterized by low predominance of C27 steranes and slightly high abundance of C28 and C29 indicating that the Meleiha oil is believed to be generated from both marine shales and carbonates enriched in marine algae with more contribution from terrestrial organic sources deposited under saline conditions. It reveals that the Meleiha oil is derived mainly from terrestrial organic sources.

The specific geochemical parameters have been assessed by the aid of gas chromatography and gas chromatographic-mass spectrometric analyses of the saturated fractions. The degree of the correlation between crude oils and the extracted samples was determined by studying the correlation scores for both oils and extracts. Eight correlation parameters have been studied for this purpose includes: saturates%, saturates/aromatics ratio, Cmax, C21+C22/C28+C29, CPI, pristane/phytane, pristane/*n*-C17 and pristane+*n*-C17/phytane+*n*-C18. An overall correlation score was obtained for each oil and extract by summing up the contribution from each parameter. The GC/FID chromatogram of the Meleiha crude oil sample is characterized by a monotonically decreasing homologous series of heavy normal alkanes (*n*-C25 to *n*-C30) and display odd carbon preference at *n*-C15 which reflects mature oils originated mainly from non-marine origin mainly terrestrial organic matters deposited under slightly oxidizing environment and slightly mixed with inputs from marine source (Hunt, 1996). The mode of distribution of *n*-paraffins in the crude oils of Misaada and Qarun oilfields show that the maximum abundance is at *n*- C15 to *n*-C25

The steranes distribution of crude oils was studied. Meleiha crude oil was found to be characterized by low predominance of C27 steranes and slightly high abundance of C28 and C29 indicating that the Meleiha oil is believed to be generated from both marine shales and carbonates enriched in marine algae with more contribution from terrestrial organic sources deposited under saline conditions. It reveals that the Meleiha oil is derived mainly from

Fig. 7. Map of Egypt showing the main oil and gas fields.

reflecting marine origin.

terrestrial organic sources.

The high concentrations of C27 - C29 diasteranes in case of Meleiha oil indicate input of marine organic source with more contribution from terrestrial organics (Waples and Machihara, 1992). The high diasteranes concentration compared to regular steranes suggest a clay rich source rock because the clay is required to catalyze the steroids transformation to diasteranes (Peters and Moldowan, 1991). Misaada and Qarun oils are characterized by slightly lower predominance of C27 steranes and higher abundance of C28 and C29 steranes indicating inputs from marine organic sources (Waples and Machihara, 1992). Moreover, the distributions of regular steranes C29, C27 and C28 on the ternary diagram reveal also more contribution from marine organic sources. The diasteranes concentrations compared to regular steranes is low, suggesting a clay rich source rock.

The crude oil samples of Qarun and Misaada oilfields have Pr/*n*-C17 and ph/*n*-C18 ratios 0.28, 0.47 and 0.1, 0.1, respectively reflecting mostly mature and originated mainly from marine organic sources deposited under reducing environment. The crude oil of Meleiha oilfield has Pr/*n*-C17 and ph/*n*-C18 of 0.40 and 0.28 indicating mixed organic sources.

Terpanes biomarkers distributions derived from the m/z 191 mass chromatograms show that the C21-C25 tricyclic terpanes of Meliha oil appear to be the largest components which may support that the oil of Meleiha oilfield is more mature and sourced mainly from marine carbonate source rocks. At the same time, the C23, C24 and C25 tricyclic terpanes are generally of lower values compared with C22 indicating that the oil has some inputs from terrestrial organic materials (Hunt, 1996). The unusual low amounts of C30 extended hopanes seem to be associated with mixed organic sources (Moldowan et al., 1985). This phenomenon can be displayed by the low ratio of C29/C30 extended hopanes.

On the other hand, The C30 hopanes are the largest components in the series C27-C34 in oil samples from Misaada and Qarun oilfields. This indicates that the organic materials in these oils were originated mainly from saline and hypersaline environments (Peters and Moldowan, 1993). The extended hopanes are available as paleo environmental indicator (Waples and Machihara, 1992). The unusual large amounts of C30 hopanes seem to be associated with marine sources (Moldowan et al., 1985).

Bisnorhopanes are types of pentacyclic triterpanes present in significant concentrations in oil. Bisnorhopanes are observed in Guatemalan evaporites and frequency reported in other biogenic siliceous rocks of the circum-Pacific region (Connan et al., 1986). It is believed that sediments containing large amounts of bisnorhopane were deposited under anoxic conditions (Mello et al., 1988). The crude oils of Misaada oil field have relatively higher amounts of C28 bisnorhopane indicating more anoxic environment than Qarun and Meleiha oils.

Carbon preference index (CPI) values of the studied crude oils are close to unity, ranging from (0.94 to1.04) indicating mature crude oils.

Pr/Ph ratio of the oil sample from Meleiha oilfield is 3.0 indicating oxidizing depositional environment of the crude oil while the crude oils from Qarun and Misaada oil fields have Pr/Ph ratios of 0.63 and 2.00 respectively reflecting that these crude oils were deposited under transitional (reducing– oxidizing) environments. These results indicate good correlation between crude oils from Qarun and Misaada oilfields with slight correlation to crude oil from Meleiha oilfield.

Oil: source correlation reflect a good correlation between the extract samples of Kharita and Khatatba source rocks and crude oils from Meleiha and Qarun oilfields. The extract of

Biomarkers 181

parameters based on various sterane isomerisation distributions and polycyclic aromatic compounds indicate a low thermal maturation level for the generated hydrocarbons within the syn-rift lithostratigraphic succession. These similarities in geologic occurrences and biomarker characteristics suggest the possibility that the hydrocarbon expulsion could have been initiated from deeply buried Miocene source rocks and trapped within the syn-rift

(Barakat et al., 2000) studied the aliphatic and aromatic fractions of a beach tar sample from the Mediterranean coast of Sidi Kreir, 37 Km west of the city of Alexandria 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

structures throughout the extensional faults of the central Gulf of Suez province.

evaporite source depositional environment under normal saline reducing conditions.

Although oil is the dominant energy source, oil spill occurs worldwide causing a severe global environmental problems (Abostate et al., 2011). Egypt is suffering from oil pollution owing to the increasing petroleum activities in the last decades. Environmental protection is currently an important subject of increasing public and research concern and as a result, special efforts have already been done so as to develop oil spill detection and fingerprinting. Therefore, to unambiguously characterize, identify, categorize, and quantify all sources of hydrocarbons entering the environment is very important for environmental damage assessment, evaluation of the relative risks to the ecosystem posed by each spill and selecting appropriate spill response and taking effective cleanup measures. Biomarkers are the most important hydrocarbon groups for chemical fingerprinting which play a very important role in source identification in environmental forensic investigations of oil spills. It was a useful analogy to explain this type of forensic analyses for spilled oil. However, it was recognized then, and remains true today, that the analyses of spilled oils do not have the statistical discriminating power of the human fingerprint in the sense that each human has an individual fingerprint. Analyses of spilled oils and potential sources are usually undertaken by increasingly sophisticated chemical analyses until either all but one potential source oil remains that cannot be distinguished from the spilled oil, or all potential sources have been eliminated and the spill is then a "mystery". The presumption for success using fingerprinting is that a complete collection of possible sources has been secured for the matching analyses. The term "passive tagging" has been used in place of fingerprinting in the past to describe the chemical analyses of oils. The term derives from the process of using the chemicals naturally present in the oil as "tags". The "passive" part of the term was used because there were proposals and some experiments conducted in the late 1960s and early 1970s to introduce "active tags" into various oil cargos to allow for identifying the oils if they were spilled (Adlard, 1972). Various chemicals were proposed as active tags, but the obvious international administrative and logistical effort needed to keep track of such

**Applications of biomarkers in oil spill source identification** 

"active tags" prevented operational use of active tagging systems.

Nothing sparks concerns about contaminates in the environment quite like a petroleum release. Unfortunately, the events of 2010 served to heighten the awareness and need to

**9. Current work** 

Bahariya source rock shows slight correlation with Meleiha oil and differ from the other oil samples. These evidences indicate that Kharita and Khtataba source rocks seem to act as sources and reservoirs for oil generation in the Qarun and Misaada oilfields while the oil generation of Meleiha oilfield seems to be migrated from Bahariya source rocks.

#### **8.2 Suez Gulf**

The Gulf of Suez occupies the northwestern arm of the Red Sea between Africa proper (west) and the Sinai Peninsula (east) of Egypt. The length of the gulf, from its mouth at the Strait of Jubal to its head at the city of Suez, is 195 miles (314 km) and it varies in width from 12 to 20 miles (19 to 32 km). Because the importance occurrence of crude oil in the Gulf of Suez, the biological markers was analyzed to evaluate the geochemical relationships between the oils recovered from some oil fields within the Gulf of Suez to assess and investigate oil characterization, maturation, source depositional environments and oil families.

Roushdy et al. (2010) evaluate the geochemical relationships between the oils recovered from some oil fields within the Gulf of Suez. This target was achieved through analytical results of GC and GC-MS analysis for seven crude oil samples collected from seven oilfields namely: Ras Badran, Belayim marine, Belayim Land, Rahmi, West Bakr, Esh El Mellaha and Geisum distributed within the Gulf of Suez. These samples are representative for the producing horizon zones (Belayim, Rudies and Nuhkul formations.) of Upper- Lower Miocene age characterized by limestone facies with depths ranging from 2250 to 8286 ft. Geochemical parameters based upon acyclic isoprenoids, steranes and terpanes coupled with bulk geochemical parameters indicated whether the crude oils are of marine, terrestrial or mixed marine-terrestrial origin.

Biomarkers analyses of crude oils from the Gulf of Suez suggest that oils are more mature and derived mainly from mixed organic sources from terrestrial and marine inputs contribution to the biomass from algae and plankton in different saline environments.

A few discrepancies that appear between the results obtained by using the different parameters can be related to the alteration caused by the number of processes (physical, chemical and/or biological) affecting part of the source related biomarkers pattern of the oil after generation and/or primary migration from the source rock.

In another study, two genetic families based on biomarker analyses of oils were isolated from the Gulf of Suez, Egypt. Oils from Ras Fanar and East-Zeit wells have high gammacerance, low diasterances and high C33/C34 hopanes, consistent with an origin from the Brown Limestone. Oils from the Gama and Amal-9 wells have low gammacerance, high diasterances and oleanane indices > 20 %, indicating an angiosperm-rich Tertiary siliciclastic source rock, probably the Lower Miocene Rudeis Formation (Peters et al., 2005).

(Younes et al., 2004) evaluated the depositional environments and maturation assessments of source rocks from the central Gulf of Suez, Egypt utilizing the biomarker distributions in nine crude oils derived from a synrift tectonic sequence of the central Gulf of Suez province. No obvious variations were observed amongst the studied crude oils, suggesting that these oils are all of the same genetic type. These oils features, a predominance of oleanane, reaching 24%, and a relatively low gammacerane concentration of 10%, suggested that these oils were derived from a terrigenous organofacies source rock with a significant angiosperm higher land plants input deposited within the marginally mature syn-rift shale of Lower Miocene Nukhul, Rudeis and Kareem formations of mixed kerogen types II-III. Maturity

Bahariya source rock shows slight correlation with Meleiha oil and differ from the other oil samples. These evidences indicate that Kharita and Khtataba source rocks seem to act as sources and reservoirs for oil generation in the Qarun and Misaada oilfields while the oil

The Gulf of Suez occupies the northwestern arm of the Red Sea between Africa proper (west) and the Sinai Peninsula (east) of Egypt. The length of the gulf, from its mouth at the Strait of Jubal to its head at the city of Suez, is 195 miles (314 km) and it varies in width from 12 to 20 miles (19 to 32 km). Because the importance occurrence of crude oil in the Gulf of Suez, the biological markers was analyzed to evaluate the geochemical relationships between the oils recovered from some oil fields within the Gulf of Suez to assess and investigate oil

Roushdy et al. (2010) evaluate the geochemical relationships between the oils recovered from some oil fields within the Gulf of Suez. This target was achieved through analytical results of GC and GC-MS analysis for seven crude oil samples collected from seven oilfields namely: Ras Badran, Belayim marine, Belayim Land, Rahmi, West Bakr, Esh El Mellaha and Geisum distributed within the Gulf of Suez. These samples are representative for the producing horizon zones (Belayim, Rudies and Nuhkul formations.) of Upper- Lower Miocene age characterized by limestone facies with depths ranging from 2250 to 8286 ft. Geochemical parameters based upon acyclic isoprenoids, steranes and terpanes coupled with bulk geochemical parameters indicated whether the crude oils are of marine, terrestrial

Biomarkers analyses of crude oils from the Gulf of Suez suggest that oils are more mature and derived mainly from mixed organic sources from terrestrial and marine inputs contribution to the biomass from algae and plankton in different saline environments.

A few discrepancies that appear between the results obtained by using the different parameters can be related to the alteration caused by the number of processes (physical, chemical and/or biological) affecting part of the source related biomarkers pattern of the oil

In another study, two genetic families based on biomarker analyses of oils were isolated from the Gulf of Suez, Egypt. Oils from Ras Fanar and East-Zeit wells have high gammacerance, low diasterances and high C33/C34 hopanes, consistent with an origin from the Brown Limestone. Oils from the Gama and Amal-9 wells have low gammacerance, high diasterances and oleanane indices > 20 %, indicating an angiosperm-rich Tertiary siliciclastic

(Younes et al., 2004) evaluated the depositional environments and maturation assessments of source rocks from the central Gulf of Suez, Egypt utilizing the biomarker distributions in nine crude oils derived from a synrift tectonic sequence of the central Gulf of Suez province. No obvious variations were observed amongst the studied crude oils, suggesting that these oils are all of the same genetic type. These oils features, a predominance of oleanane, reaching 24%, and a relatively low gammacerane concentration of 10%, suggested that these oils were derived from a terrigenous organofacies source rock with a significant angiosperm higher land plants input deposited within the marginally mature syn-rift shale of Lower Miocene Nukhul, Rudeis and Kareem formations of mixed kerogen types II-III. Maturity

source rock, probably the Lower Miocene Rudeis Formation (Peters et al., 2005).

after generation and/or primary migration from the source rock.

generation of Meleiha oilfield seems to be migrated from Bahariya source rocks.

characterization, maturation, source depositional environments and oil families.

**8.2 Suez Gulf** 

or mixed marine-terrestrial origin.

parameters based on various sterane isomerisation distributions and polycyclic aromatic compounds indicate a low thermal maturation level for the generated hydrocarbons within the syn-rift lithostratigraphic succession. These similarities in geologic occurrences and biomarker characteristics suggest the possibility that the hydrocarbon expulsion could have been initiated from deeply buried Miocene source rocks and trapped within the syn-rift structures throughout the extensional faults of the central Gulf of Suez province.

(Barakat et al., 2000) studied the aliphatic and aromatic fractions of a beach tar sample from the Mediterranean coast of Sidi Kreir, 37 Km west of the city of Alexandria 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.
