Distribution of triterpanes and steranes biomarkers as indication of organic matters input and depositional environments of crude oils of oilfields in Gulf of Suez,Egypt

Eight crude oils collected from different oilfields distributed within the northern, central and southern Gulf of Suez basin to detect the distribution of triterpanes and steranes biomarkers as indication of organic matter input and depositional environments of crude oils and lithology of organic matters. This achieved throughout the application of gas chromatography mass spectrometry analysis. The results revealed that the Gulf of Suez samples are believed to be of marine organic matter input deposited under anoxic depositional environment. Off shore samples S3 and S4 from Central Province of Gulf of Suez basin show low maturity levels, while the other samples which were of higher maturity levels.     

The Nature of Pre-Miocene and Miocene Sediments in the Offshore Northern Part of the Gulf of Suez,Egypt

The present study deals with subsurface geology pre-Miocene and Miocene rock units penetrated in the extremely northern offshore Gulf of Suez area. Throughout the pre-Miocene and Miocene, changes in the tectonic pattern, depositional environment, and sediment types indicate different magnitudes and tectonic instability. Based on the available seven dry subsurface composite well logs (GS 9-1, Darag 17-1, GS 24-1, X 80-1, GS 56-1, Fina Z 80-1A, and GS78-1 wells) besides dipmeter logs, 39 stratigraphic maps (isopach and facies maps) are constructed to show thickness variations, facies changes, and paleogeology of Jurassic (Massajid Formation), Lower Cretaceous (Nubia Formation), Upper Cretaceous (Raha, Abu Qada, Wata, Matulla, and Sudr formations), Lower Miocene (Nukhul, Rudeis, and Kareem formations), and Middle Miocene (Belayim, South Gharib, and Zeit formations) times. Moreover, two cross sections are constructed to show thickness and lateral variations in facies changes and tectonics affecting the area at that time. Despite this, the study area has suitable conditions for hydrocarbon generation and accumulation, the seven wells drilled in the study area are considered to be dry or nonproductive. They are considered to be dry or not productive due to tilting of strata to the SW direction, absence of cap rocks (evaporites and salts) and shale in most parts of the study area (especially in the extremely northern parts), and affecting the area by a large numbers of normal faults due to active and continuous tectonic events on the Gulf of Suez area. These reasons may be aided to the migration of hydrocarbons from the area to outside and to the adjacent oil fields.     

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.     

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

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.     

苏伊士湾中新统蒸发岩储层特征及有利区预测

苏伊士湾中新统蒸发岩广泛发育,部分钻井在蒸发岩层系测试获得工业油流,展示出良好的油气勘探开发前景。为了厘清蒸发岩层系储层特征及展布规律,以埃及North West Gemsa区块中新统South Gharib组为例,利用岩心、铸体薄片、压汞实验、物性分析及测井资料等,对SG组岩性及储层特征进行研究。结果表明:SG组岩石类型多样,以盐岩为主,夹硬石膏、杂卤石、光卤石及白云岩等;储集空间主要为晶间孔,样品压汞曲线形态及孔喉半径分布显示出细歪度、微细喉等特征,渗流条件较差;白云岩及叶片状硬石膏物性条件相对较好,为研究区重要的储层发育岩石类型,其余蒸发岩类物性整体较差,一般不能作为储层;有利储层分布区主要位于区块西部,为SG组下步勘探重点区域。该研究成果对苏伊士湾地区中新统蒸发岩层系的油气勘探开发具有重要指导意义。     

Applications of biological markers in assessing the organic richness of the surface sediments of Suez Gulf,Egypt

The semienclosed Suez Gulf records various signals of high anthropic pressures from surrounding regions and the industrialized Suez countries. The sedimentary hydrocarbons have been studied in six coastal stations located in the Gulf of Suez. Nonaromatic hydrocarbons were analyzed by GC/FID and GC/MS to assess organic content in surface sediments of Suez Gulf, Egypt, depending on alkane, terpane, and sterane biological marker indicators. The results showed that the hydrocarbons are originated from multiple terrestrial inputs, biogenic and pyrolytic. Several ratios hydrocarbons indicated the predominance of petrogenic in combination with biogenic hydrocarbons.     

Bulk Compositions,Genetic Origin,Classifications, and Maturation of Crude Oils in the Gulf of Suez,Egypt

Abstract

API gravity, sulfur content, gas chromatography, and gas chromatography-mass spectrometry analyses were carried out for eight oil samples collected from different wells in the Gulf of Suez. The results showed that two types of oils could be recognized: (a) heavy oils, which are oils from Zafarana, Rahmi, West Bakr, and Ras Gharib wells, are of low maturation and originated mainly from terrestrial organic sources; and (b) light oils, which are oils from Um El Yuser, Ras El Ush, Gemsa-SE, and Hurghada wells, have a high level of maturation and orginate mainly from marine organic sources.     

Significance of GC/FT-IR and GC/MS in recognizing the sources of organic materials from sediments along the Suez Gulf Shoreline,Egypt

The present work aims to using the application of GC, GC/MS, UV, and FT/IR spectroscopy organic matters extracted from sedimentary hydrocarbons from six coastal stations located in the Gulf of Suez and proposed to evaluate hydrocarbons in the sediments. The results the origins of hydrocarbons are multiple sources from terrestrial inputs, biogenic, and pyrolytic. Abundance of vascular plant n C₂₃– n C₃₃ alkanes with a high odd-to-even predominance, pristane, and phytane beside nC₂₉/nC₁₇ ratios and the presence of biogenic hopanes indicate the predominance of biogenic in combination with petrogenic hydrocarbons. FT-IR spectroscopic analysis indicates high concentrations of aliphatic hydrocarbons as well as mono- and polynuclear aromatic hydrocarbons are useful tool in organic geochemistry studies. UV analysis for organic matters incorporated in sediments reveals that oil pollutants have considerable amounts of aromatic compounds.     

Source rock evaluation and organic geochemistry of Belayim Marine Oil Field,Gulf of Suez,Egypt

Geochemical evaluation of Belayim Marine Oil Field using TOC and Rock Eval Pyrolysis investigations for a total of 19 cutting samples (9 samples covering (Nubia-B Formation) from well BM-57, and 10 samples covering (Nubia-A, B Formations) from well BM-65) was performed. Furthermore, geochemistry analyses of two crude oil samples from Wells BM-29 and BM-70, which are recovered from the Upper Rudeis Formation were performed. The BM-70 oil sample is recovered by Drill Steam Testing, while the BM-29 oil sample is taken from the flow output. Moreover, the oil samples were subjected to GC/GC-MS analysis (Biomarker) by StratoChem Company.In general, TOC analyses showed that the Nubia-A and B formation sediments are fairly immature compared to good source rocks with very high Hydrogen Index indicative of kerogen type II. The geochemical investigations of two oil samples indicate that the Upper Rudeis oil of Belayim Marine was derived from a marine carbonate rich source, which is relatively rich in algal organic matter and has moderate sulfur content. The maturity of the analyzed oils (about 0.75% R0) falls short from the stage of peak hydrocarbon generation which is known to be reached at about 0.85% R0.     

“Detection and characterization of fractures in the Eocene Thebes formation using conventional well logs in October field,Gulf of Suez,Egypt”

Fractures are one of the most prevalent and important geological features in petroleum exploration and production, as they have a substantial impact as conduits for hydrocarbon flow and improve the overall permeability of the formation. Despite their necessity, detecting and characterizing natural fractures still represents a difficult challenge. This study provides a technique for detecting and characterizing naturally fractured reservoirs using conventional well logs in the Eocene Thebes Formation, October Field, Gulf of Suez. Especially as this technique is not applied widely in October Field or even in the Gulf of Suez. Most carbonate reservoirs are complex and heterogeneous; one of the reasons is their naturally fractured characteristics. These fractures can significantly affect reservoir behavior, performance, and production. Despite being the most commonly available data source, logs are rarely employed in a systematic way to have a complete quantitative analysis of naturally fractured reservoirs. Since the presence of fractures affects all well logs in one way or another. This study presents an integrated workflow for determining fracture presence potentiality by combining conventional well logs, thin sections, and other available data in absence of directly advanced logging technologies such as Formation MicroImager (FMI), Dipole Shear Image (DSI), and Borehole Televiewer (BHTV). This integrated workflow was very effective and useful in the evaluation of potential fractures' existence, reservoir characterization, and development. Finally, the results of this integrated workflow suggest a high probability of fracture existence and identification in Thebes Formation, confirming that integration between conventional logging and other available data is very precious, and has a good potential to be used in absence of direct advanced methods for fractured reservoir characterization. For further studies, core data and advanced logs would be beneficial for correlation, since they would provide a more accurate picture of the fracture parameters.     

PETROLEUM SYSTEMS ANALYSIS OF THE EASTERN ARABIAN PLATE: CHEMOMETRICS BASED ON A REVIEW OF THE GEOCHEMICAL CHARACTERISTICS OF OILS IN JURASSIC – CENOZOIC RESERVOIRS

This paper presents the results of an integrated geochemical study of oils in Jurassic – Cenozoic reservoirs in the eastern region of the Arabian Plate. The main objective was to analyze the active petroleum systems at a regional scale across the study area which extends from NE Iraq to SE Oman and includes the entire Persian Gulf. The dataset for the study consisted of more than 500 crude oil samples from 112 oil fields and 11 different reservoir units. This dataset was compiled from both the literature and re-evaluated geochemical and stable isotope analyses, augmented by new analytical studies. The study documents regional variations and trends in the bulk and molecular properties and stable isotope ratios of the oil samples. Two overall clans and twelve genetic oil families and sub-families were distinguished using multivariate statistical analysis (chemometrics) based on biomarker parameters. The age, lithology, depositional setting and organic matter type of the respective source rocks for each family/sub-family was inferred from oil geochemical fingerprints. The results provide insights into the key geological factors that control the number, size and geochemical character of oil fields in the eastern Arabian Plate. The geographical extent of the various oil families was assessed and used to evaluate charge access and to predict migration directions and migration pathways in the study area. The results indicate the value of implementing multivariate statistical analysis on “big data” along with state-of-the-art geological petroleum systems analysis and interpretation of biomarker and oil composition data to investigate complex and extended petroleum systems.