Biomarkers Assessment of Crude Oils and Extracts from Jurassic-Cretaceous Rocks,North Qattara Depression,North Western Desert,Egypt

Abstract

Crude oils together with extracts from the Middle Jurassic (Khatatba Formation), Barremian-Early Aptian Alam El Bueib Formation, and Early Albian Kharita Formation were collected from five wells (Ras Qattara-Zarif-5, Ras Qattara-Zarif-3, and Zarif-1, Zarif-2, SW Zarif-1) in the North Qattara Depression. Biomarkers (pristane/phytane, isoprenoids/n-alkanes, steranes, triterpanes, C₂₉ steranes 20S/20S + 20R, C₂₃ tricyclic/C₃₀ hopane, Ts/Tm, C₃₀ moretane/C₃₀ hopane ratios, homohopane and gammacerane indices) of the saturated hydrocarbon fraction were analyzed in order to assess the source and maturity of the crude oils and the extracts. The results suggested that the oils from Khatatba and Alam El Bueib formations are mature, derived from source rocks containing marine and terrestrial organic matter, respectively. The source environments and maturity of the oil from the Khatatba Formation is similar to that of the Khatatba source rock extract. The oil from the Alam El Bueib formation differs from the extracts of the Alam El Bueib and Kharita formations. The Khatatba formation seems to be an effective source rock in the North Qattara Depression.     

Application of Light Hydrocarbon (C7+) and Biomarker Analyses in Characterizing Oil from Wells in the North and North Central Sinai,Egypt

Abstract

Seven representative oil show samples from wells in the north and north central Sinai have been characterized by means of a variety of organic geochemical techniques (C₇ hydrocarbon and biomarker analyses), to illustrate origin, differences, and similarity among oils. These oils were obtained from Cretaceous and Jurassic reservoirs. The C₇ oil correlation star diagram (OCSD) suggests closely related oils, derived mainly from similar source rocks, while the C₇ oil transformation star diagram (OTSD) and C₇ light hydrocarbon analyses indicate a minor degree of transformation of some oils, as Misri-1, Halal-1, and Nakhl-1 oils were subjected to evaporative fractionation. Moreover, the studied oils show no sign of water washing and biodegradation. Molecular characteristics suggest pre-Tertiary shales and carbonate source rocks, deposited under a saline oxic environment, rich in terrigeneous organic sources with significant bacterial and algal input. Since the studied oils are of mixed marine and terrestrial origin, C₇ signature of these oils is not representative of their origin and should be supported by other geochemical evidence (e.g., biomarkers) to predict their origin.     

Bulk Geochemical Characteristics of Crude Oils From Wells in the North Western Desert,Egypt

Abstract

Different oil samples were collected from oil fields in the North Western Desert; namely, Meleiha, Razaak, and North Qarun fields. These oils were analyzed geochemically, including sulfur content, American Petroleum Institute (API) gravity, and gas chromatography The results showed that API gravity and sulfur content indicate that the crude oils have high mature level of marine origin. Distribution of n-alkanes (Carbon Preference Index [CPI], pr/ph, and isoprenoide/n-alkanes ratios) reflects that the oil samples originated mainly from marine organic sources deposited in a reducing environment. This indicates that the oil samples under investigation are well correlated with each other in the western part of the North Western Desert.     

Oil Families and Their Potential Sources in the Southern Gulf of Suez,Egypt

Abstract

Four oil families are identified in the southern Gulf of Suez, through high-resolution geochemical studies including gas chromatography, gas chromatography–mass spectrometry, and carbon isotope analyses. Biological features characterize oils in family 1a, suggesting tertiary carbonate source rocks for these oils, rich in type II organic matter and deposited under anoxic depositional environment. Family 1b oil shows minor variations in the source of organic matter and the depositional environment, as it was derived from carbonate source rock with more algal and bacterial contribution and minor input of terrestrial organic sources, deposited under less saline condition compared to family 1a oil. Family 2 oil, although genetically related to family 1a oil, has some distinctive features, such as diasterane to sterane and pristane to phytane ratios, which suggest clay-rich source rocks and a more oxic depositional environment. Also, the lack of oleanane indicates pre-tertiary source rocks for this oil. In contrast, family 3 oil is of mixed sources (marine and non-marine), generated from low sulfur and clay-rich source rock of tertiary and/or younger age. Family 4 oil seems to be mixed from family 1b and family 3 oils, sourced mainly from carbonate source rocks rich in clay minerals with algal and bacterial contributions. Family 4 oil is highly mature, family 1b oil lies within equilibrium values (peak oil generation stage), while the other families are more or less near equilibrium.     

Characterization and correlation of crude oils from some wells in the North Western Desert,Egypt

Characterization and correlation of crude oils from some wells in the North Western Desert, based on six crude oil samples, were studied by different analytical techniques, including API gravity, sulfur content, nickel and vanadium, bulk compositions and saturated fraction obtained from gas chromatography have been studied. The results show that the crude oils are normal to medium aromatic oils, with high API gravity and high sulfur content. V, Ni, V/Ni and V/(V + Ni) reflecting oils might be sourced from non-clastic source rocks, possibly carbonates, deposited under anoxic-suboxic conditions. Bulk compositions revealing that the crude oils were derived from marine organic sources. While, the paraffins and naphthenes percent indicates that the oils belong to paraffinic to naphthenic oil types, deposited in slightly anoxic to suboxic conditions and contained marine organic matter. Thermal maturity data showed that the oil samples were generated from mature source rocks. This indicates the studied oil samples are well correlated with each other, where they are similar in their oil type maturation and source depositional environments.     

SOURCE ROCK EVALUATION AND GEOCHEMISTRY OF CONDENSATES AND NATURAL GASES, OFFSHORE NILE DELTA, EGYPT

Geochemical analyses of mudstones from wells in the NE offshore Nile Delta suggest that the Early Miocene Qantara Formation has "good" potential to generate hydrocarbons at the studied locations. Its generating capability and oil-proneness increase northwards, towards areas where better organic-matter preservation and a greater contribution from marine source material can be expected. By contrast, the Middle Miocene Sidi Salem Formation has "poor to fair" potential to generate mixed gas and oil, while the overlying Wakar and Kafr El Sheikh Formations have "poor" capability to generate gas with minor oil. Based on pyrolysis T_max and thermal alteration index assessments, the Wakar and Kafr El Sheikh Formations are immature in the study area. The Sidi Salem and Qantara Formations are immature in the southern part of the study area, but are within the oil window in the north, around well Temsah-4.
Biomarker distributions based on GC-MS analyses of two condensate samples from the Wakar and Sidi Salem Formations indicate that hydrocarbons are derived from siliciclastic source rocks containing significant terrestrial material and limited marine organic matter. The condensates were generated during early maturation of Type III kerogen from deeper and more mature source rocks than those encountered in the drilled wells. Geochemical and isotopic data from natural gas produced from the Kafr El Sheikh Formation suggest mixed biogenic and thermogenic sources.     

Source Rocks Evaluation of Sidi Salem-1 Well in the Onshore Nile Delta,Egypt

Abstract

Ten core samples representing the subsurface formation of Sidi Salem well No. 1, in the onshore Nile Delta, Egypt. The samples were subjected to comprehensive organic geochemical studies (such as rock-eval pyrolysis, gas chromatograph [GC] and gas chromatography-mass spectrometry [GC-MS]) aiming to evaluate potential source rocks, organic matters types, depositional environments, and maturation. The results revealed that the source rocks in the drilled sections are marginally mature to mature zone and have fair to good potential for generating oil and gas. These rocks are dominated by organic matter derived mainly from mixed organic matters (marine and terrestrial) with contributions from algae and bacteria deposited under anoxic to suboxic saline environments.     

Crude Oil Geochemistry and Its Relation to the Potential Source Beds for Some Meleiha Oil Fields in the North Western Desert, Egypt

The results of the geochemical evaluation for eleven crude oil samples from some Meleiha oil fields revealed that, these oils have high specific gravity (°API), low sulfur content and rich in saturated hydrocarbons. Two oil classes were recognized. The first is carbonate oils of high maturity level, originated from marine origin. The second, deltaic oils of moderately level of maturation, derived mainly from terrigenous sources. Oil: source correlation for the productive oils and the extracts of the potential source beds revealed a genetic close relationship between oils and extracts of Khatatba and Alam El Bueib formations. This indicates that the source of the oils in the study area may be related to mixed sources of these formations.     

A Review of: “Electrochemical Hydrogen Technologies”Edited by Hartmut Wendt Elsevier Science Publishers,B.v,Amsterdam, The Netherlands 1990, xx + 512 pp.

Abstract:

The organic geochemical and biomarker analyses of the Miocene source rocks of some wells in the onshore Nile Delta, suggested that the Abu Madi Formation has poor immature to marginally mature source rocks of Type III Kerogen deposited under the terrestrial environment. The Sidi Salem Formation has fair-to-good mature source rocks of producing mixed oil and gas, originating mainly from marine organic sources. The Moghra Formation has mature good source rocks for Type (II/III) kerogen, derived from organic matter and rich in both terrigeneous and marine sources. The geochemistry of condensates revealed that the Abu Madi and Moghra condensates originated from marine organic matters with little input from a terrestrial source, while Sidi Salem condensate was derived from more contribution of terrestrial organic matters. Abu Madi condensate is less mature than Sidi Salem and Moghra condensate. The geochemical thermal modeling of the Miocene source rocks indicates that the Abu Madi formations are in the early stages of hydrocarbon up until the present time, while Moghra and Sidi Salem formations are in the mature stage of hydrocarbon generation up until the present time. This indicates that the studied condensates have probably migrated from deeply buried source rocks which are at a higher level of maturity rather than from less mature source rocks in the study area.     

Organic and Carbon Isotope Geochemistry of Crude Oils from Ashrafi Field,Southern Gulf of Suez Province,Egypt: Implications for the Processes of Hydrocarbon Generation and Maturation

Abstract

Four crude oil samples representing the Miocene formations of Belayim, Kareem, and Nukhul, and the Pre-Miocene Nubia Sandstone of Ashrafi Field, offshore southern Gulf of Suez, Egypt. These crude oil samples were analyzed using a variety of organic geochemical techniques including both C₇ and whole oil Gas Chromatography (GC), Gas Chromatography–Mass Spectrometry (GC–MS) in addition to stable carbon isotopes to the saturate and aromatic fractions. The organic geochemical results revealed that the Miocene and Pre-Miocene Nubia Sandstone oils generated from two different source rocks subjected to different maturation levels. The Miocene crude oil possesses geochemical properties rich in tricyclic terpanes and extended hopanes typical characteristics of oils generated from marine siliciclastic source rocks with angiosperm land plants input like Rudeis Formation as indicated from the oleanane index which exceeds 30% and low gammacerane index around 10%. Meanwhile the Pre-Miocene crude oil correlates with the marine carbonate sources of high salinity waters like Brown Limestone of Upper Cretaceous age as indicated from the oleanane index <10% and high gammacerane index >30%. The maturity parameters based on both ratios of 20S/(20S + 20R)-C₂₉ ααα cholestane and TAS/(MAS + TAS) were found to be around 0.5 for the Miocene crude oils, meanwhile both the ratios for the Pre-Miocene crude oil were >0.5. The concluded results further support the very high maturation level of the Pre-Miocene crude oil than the Miocene crude of Ashrafi Field which concordant with the reservoir stratigraphic depths.     

Source Rock Characterization Within the Stratigraphic Settings of the Orange Basin,South Africa

abstract

The petroleum source rock potential of different system tracts of a Cretaceous unit of the Orange Basin, South Africa, was evaluated using Rock-Eval pyrolysis. Forty rock samples from eight wells were obtained within the systems tract, Lowstand System Tracts (LST), Transgressive System Tracts (TST), and Highstand System Tracts (HST), in the basin. The results revealed that LST is characterized by mainly marginally organic rich shale samples with a few organic rich rocks, variable organic matter types ranging from Type II to Type IV, and a few samples that are thermally mature but have low organic matter quality. Four samples from two wells (A_F1 and O_A1) in the LST had good petroleum generative potential but were not sufficiently mature for petroleum generation. TST is characterized with a few samples being marginally organic rich, with only one being organic rich, mainly Type III kerogen with few Type IV kerogen, and only a few samples are thermally mature that have low organic matter quality. HST is characterized by many marginally organic rich rock samples, mainly Type III with a few mixed Type II/III kerogen, and only a few samples were thermally mature. The results of this study show that the LST has the best prospect in terms of petroleum generation potential, followed by HST and TST in that order. The study also reveals that limited petroleum source rocks exist, which are also impacted by low thermal maturity levels. The basin is more gas prone than oil.     

COMPARISON OF KUWAITI CRUDE OILS,COMPOSITIONAL ANALYSIS USING GAS CHROMATOGRAPHY TECHNIQUES

Abstract

High resolution capillary gas chromatography studies, were performed to compare and group oils from three different Kuwaiti wells completed in the same structural sand. These groupings contributed to the identification of the nature, origin and maturity of the crudes under study. Analysing the fingerprint gas chromatograms of the three Kuwaiti crude oils, it was found that the crudes are from a carbonate rock source origin. The chromatographic fingerprints showed that two of these crudes are almost identical in composition and belong to the same reservoir, while the other crude is different in its composition reservoir source.     

BIOMARKER GEOCHEMISTRY OF PALEOGENE CRUDE OILS AND SOURCE ROCKS FROM THE RAOYANG SAG,BOHAI BAY BASIN,NE CHINA: AN OIL – SOURCE ROCK CORRELATION STUDY

This study presents a systematic geochemical analysis of Paleogene crude oils and source rocks from the Raoyang Sag in the Jizhong sub-basin of the Bohai Bay Basin (NE China). The geochemical characteristics of fifty-three oil samples from wells in four sub-sags were analysed using gas chromatography (GC) and gas chromatography – mass spectrometry (GC-MS). Twenty core samples of mudstones from Members 1 and 3 of the Eocene-Oligocene Shahejie Formation were investigated for total organic carbon (TOC) content and by Rock-Eval pyrolysis and GC-MS to study their geochemistry and hydrocarbon generation potential. The oils were tentatively correlated to the source rocks. The results show that three groups of crude oils can be identified. Group I oils are characterized by high values of the gammacerane index and low values of the ratios of Pr/Ph, Ts/Tm, 20S/(20S+20R) C₂₉ steranes, ββ/(ββ+αα) C₂₉ steranes, C₂₇ diasteranes/ C₂₇ regular steranes and C₂₇/C₂₉ steranes. These oils have the lowest maturity and are interpreted to have originated from a source rock containing mixed organic matter deposited in an anoxic saline lacustrine environment. The biomarker parameter values of Group III oils are the opposite to those in Group I, and are interpreted to indicate a highly mature, terrigenous organic matter input into source rocks which were deposited in suboxic to anoxic freshwater lacustrine conditions. The parameter values of Group II oils are between those of the oils in Groups I and III, and are interpreted to indicate that the oils were generated from mixed organic matter in source rocks deposited in an anoxic brackish–saline or saline lacustrine environment. The results of the source rock analyses show that samples from Member 1 of the Shahejie Formation were deposited in an anoxic, brackish – saline or saline lacustrine environment with mixed organic matter input and are of low maturity. Source rocks in Member 3 of the Shahejie Formation were deposited in a suboxic to anoxic, brackish – saline or freshwater lacustrine environment with a terrigenous organic matter input and are of higher maturity. Correlation between rock samples and crude oils indicates that Group I oils were probably derived from Member 1 source rocks, while Group III oils were more likely generated by Member 3 source rocks. The Group II oils with transitional characteristics are likely to have a mixed source from both sets of source rocks.     

The Volumetric Calculation of Hydrocarbons Generation of Source Rocks in the Gulf of Suez,Egypt

Regression lines obtained from TOC versus S ₂ graphs of organic rich samples were collected from Rahmi, West Bakr, Ras Gharib, and Esh El Melleha wells in the Gulf of Suez. By applying the hydrogen index values obtained from S ₂ versus TOC graph and mass balance calculations obtained from the results of Rock-Eval pyrolysis, the original hydrocarbon generative capacity and the amounts of the hydrocarbons generated are estimated. Calculation results indicate that the amounts of original hydrocarbons and the hydrocarbon generative capacities of the two methods are similar and correlated with the results of the Rock-Eval pyrolysis. This indicates that such calculations can be applied in the hydrocarbons evaluation of source rocks.     

Evaluation of possible source rocks and extracts characteristics from Safir-1x well,North Western Desert,Egypt

The pyrolysis and vitrinite reflectance estimations for fifteen shale rock tests and additionally, geochemical burial history, and gas chromatography – mass spectrometry parameters were talked about to explore the hydrocarbon generation and maturation level and time, type of hydrocarbon produced of rock units of Safir-1x well. The results assign that the Bahariya Formation is poor to great source rock to create oil and gas, with a lower thermal maturation degree than the Khatatba and Alam El Bueib formation. Alam El Bueib is viewed as good to excellent source rock for oil and gas age, having marginally high level of thermal maturation at oil window at around 40 million years. Khatatba formation achieved the oil and gas generation window at about 80 and 50 million years separately and considered excellent source rock.

The molecular gas chromatography and mass spectrometry parameters demonstrated that the extracts of source rocks reflected that the Bahariya and Alam El Bueib extracts have a mixed sources formed under transitional conditions at low grad of thermal maturation. Khatatba source rock extracts originated from marine sources formed under reducing conditions at high grade of maturation.     

Characterization of the Organic Matter for Some Crude Oils from the North Western Part of the Western Desert,Egypt

Abstract

A direct method for crude oil evaluation based on spectral techniques is demonstrated. This direct method is demonstrated for five crude oils from the north western part of the western desert, Egypt. FTIR spectroscopy was used to study the distribution of functional groups contained in the crude oil samples. Some ratios calculated from peak heights of selected infrared bands allow for a better comparison of the spectra. These ratios will be useful to give valuable informations about the origin and thermal maturation of the organic matters. ¹³C NMR spectroscopy could provide a measure of the relative proportions of crude oils aliphatic and aromatic carbons so that the technique is proving to be a valuable organic matter maturation and typing tool. The proportion of organic carbon present in aliphatic structures correlates with oil-generating potential of a source rock. These spectroscopic techniques have been used to study the entire structures of crude oil samples. They may provide valuable informations about the aromaticity and diverse functionalities which are important to find out about the thermal history of the crude oil samples.     

ISOLATION,CHARACTERIZATION AND GEOCHEMICAL SIGNIFICANCE OF PORPHYRINS IN CRUDE OILS FROM GULF OF SUEZ

ABSTRACT

Five crude oil samples, covering a wide range of maturation, were collected from the major producing fields in the Gulf of Suez area. The oil fields were West Bakr, Um-Elyse, Morgan, Ras Gharib, and Shoab Ali. Demetallated petroporphyrins and metalloporphyrins were isolated from residua] fraction > 200°C of the crude oils using acetic acid/HCl-HBr system and chromatographic adsorption method, respectively. The isolated porphyrins were characterized and estimated by UV-visible spectroscopy. The adsorption method not only isolated metalloporphyrins but also separated vanadyl porphyrins and nickel porphyrins individually. The results indicated the presence of deoxophylloerythreoetioprphyrins [DPEP] and etioporphyrins in the studied crude oil samples. The amount of vanadyl porphyrins exhibited a good relationship with the contents of both sulfur and asphaltene in the crude oils whereas no evident relation was observed with the concentration of nickel porphyrins. The effect of reservoir depth and maturation level of the crude oils on the concentration of metalloporphyrins were geochemically assessed.     

Fingerprinting of biomarker characteristics of some Egyptian crude oils in Northern Western Desert as evidence for organic matter input and maturity level assessment

This study describes the fingerprinting of crude oils from different Egyptian oil formations using gas chromatography (GC) and gas chromatography mass spectrometry (GC–MS). The samples were obtained from Gindi, Abu El gharadig, south deep Abu El gharadig, Dahab- Merier and Faghur basins from Western Desert. Diagnostic biomarkers parameters applied in this study provide evidences about the source of organic matter, the depositional environment and maturity of the studied oils. The results showed that the crude oils of Faghur basin are believed to be originated from mixed source predominately terrestrial with chief contribution of clastic rocks deposited under oxic conditions. However, the crude oils from Gindi, Abu El gharadig, South deep Abu El gharadig and Dahab- Merier basins were generated from marine carbonate source rock deposited under anoxic depositional environment.     

Biomarker characteristics of crude oils from Ashrafi and GH oilfields in the Gulf of Suez,Egypt: An implication to source input and paleoenvironmental assessments

The present work aims to evaluate the organic geochemistry of the crude oils recovered from Ashrafi and GH oilfields within the Gulf of Suez to assess and investigate oil characterization, maturation, source depositional environments and oil families. The saturated hydrocarbons were determined by gas chromatography and gas chromatography/mass spectrometry. Pristane/phytane, isoprenoids/n-alkanes, CPI, homohopane, diasteranes, gammacerane index, C29 20S/20S+20R, C29/C30 hopane and Ts/Tm are determined. The results suggest that the studied crude oils belong to marine oil and are characterized by high level of maturation and sourced mainly from organic matters of marine origin with few terrestrial inputs.     

Evaluation of the nature,origin and potentiality of the subsurface Middle Jurassic and Lower Cretaceous source rocks in Melleiha G-1x well,North Western Desert,Egypt

The present work aims to evaluate the nature and origin of the source rock potentiality of subsurface Middle Jurassic and Lower Cretaceous source rocks in Melleiha G-1x well. This target was achieved throughout the evaluation of total organic carbon, rock Eval pyrolysis and vitrinite reflectance for fifteen cutting samples and three extract samples collected from Khatatba, Alam El Bueib and Kharita formations in the studied well. The result revealed that the main hydrocarbon of source rocks, for the Middle Jurassic (Khatatba Fm.) is mainly mature, and has good capability of producing oil and minor gas. Lower Cretaceous source rocks (Alam El Bueib Fm.) are mature, derived from mixed organic sources and have fair to good capability to generate gas and oil. Kharita Formation of immature source rocks originated from terrestrial origin and has poor to fair potential to produce gas. This indicates that Khatatba and Alam El Bueib formations take the direction of increasing maturity far away from the direction of biodegradation and can be considered as effective source potential in the Melleiha G-1x well.