Inventi Rapid: Chemical Engineering Vol. 2015, Issue 1: 1-9 [ISSN 2320-1053] 2015 eche 14589, CCC: $10 © Inventi Journals (P) Ltd Published on Web 07/11/2014, www.inventi.in RESEARCH ARTICLE INTRODUCTION Oil is a complex mixture containing a large number of related compounds. The compounds present and their relative amounts are controlled by the nature of organic matter in the source rock. Philp [1] recognized that crude oils have a biogenic origin and are formed as a result of digenetic and thermal conversion of organic matter deposited in different types of sedimentary environments. The common methods for characterization of crude oils in terms of source rocks facies and depositional environments as well as their maturity and alteration stage are an important element in exploration studies. [2] The contribution has implication for the oil characterization using different parameters which have been used for this purpose. Most of these parameters are based on the analyses of American Petroleum Institute “API” gravity and sulfur compounds for the crude oil as well as saturated and aromatics hydrocarbons, pristane and phytane ratio, isoprenoids, n-alkanes and the biological markers distributions as steranes and triterpanes in the crude oils. [3] These parameters are used for comparison of oils to detect genetic relationships, depositional environments and thermal maturation. They are classified into bulk parameters including the API gravity, saturate content, concentration of the main types of hydrocarbon and asphaltene content and specific parameters including n- alkanes and isoprenoids distribution as well as biological markers obtained by gas chromatography analysis. [3] The purpose of the present study was therefore to determine the source (organic input and depositional environment), thermal maturity level for oil generation and the mechanisms controlling their accumulation). The saturated biomarker distributions have been used in an attempt to characterize the type of organo-facies, oil classes and depositional environments of the crude oils. These achieved through the geochemical analyses of oil samples, including sulfur content, API gravity, C15+ saturated and gas chromatography analysis. 1 Department, Egyptian Petroleum Research Institute, Nasr City, Cairo, Egypt. E-mail: elnady1963@live.com *Corresponding author 2 Geology Department, Faculty of Science, Zagazig University, Al Sharkia, Egypt. GEOLOGIC SETTING The Ras Gharib Oilfields covers a surface area of about 225 km in the central part of the coastal strip of the western side of the Gulf of Suez, lies between latitudes 28 о 23 ׳ -28 о 24 ׳ N and longitudes 33 о 03 ׳ -33 о 04 ׳ E (Figure 1). The geochemical characteristics of crude oils in the Gulf of Suez are discussed by Zein El Din et al., [4] reported that the oils are derived from similar marine source rocks. Roharback [5] suggested that the oils have the same genetic family, highly similar in their source rocks, as they reflect a marine origin and show no biodegradation. Shaltut et al., [6] divided the oils into two groups based on porphyin distribution; the first group is characterized by the increase in vanadyl porphyin distribution with the depth, while the second group shows inverse relation. Mostafa and Khaled [7] concluded that the reservoir depth of the oils is not correlated with the oil maturity. Mostafa and Ganze [8] revealed that the crude oils of the Rudeis oil field are similar in their origin; Barakat et al., [9] divided the oils of the southern part of the Gulf of Suez into three types. Type I is sourced from carbonate source rocks (mainly of marine origin), type II appears to be originated from Tertiary source rocks with contribution from high land plants and type III is a mixture of type I and type II. Sharaf [10] recognized two oil groups for the oils from October and Abu Rudeis fields. Heavy oil, derived mainly from hypersaline reducing environment and moderate to light oils, formed under low salinity environment with minor contribution from terrigenous organic matter. El Nady [11] recognized that the crude oils of the Gulf of Suez are sourced mainly from marine organic matters. Barakat et al., [12] stated that there is a close genetic relation between the oils in the southern part of Gulf of Suez. El Nady and Harb [13] recognized that the crude oils are mature and derived mainly from terrestrial with marine input in transitional environments. El Nady [14] reported that the crude oils in the south Gulf of Suez are mature, originated mainly from marine sources and show good correlation with the source rocks in the southern part of Gulf of Suez. El Nady et al., [15] divided the crude oils in the Gulf of Suez into two groups: moderately mature oils generated in a strongly reducing (marine) and mature oils generated from source rocks deposited in lacustrine palaeoenvironmental. Roushdy et al., [16] reported suggest that the crude oils are mature and derived mainly from mixed organic sources from terrestrial Geochemical Composition and Specific Properties of Crude Oils from Ras Gharib Oilfields in the Central Gulf of Suez, Egypt Mohamed M El Nady 1* , Fatma S Ramadan 2 , Mahmoud M Hammed 1 , Nira M Lotfy 1 Abstract: The geochemical composition, API gravity, sulfur content and asphaltene content were determined for the crude oil samples collected from Gharib-164, Gharib-163, Gharib-106, Gharib-116 wells within the Ras Gharib oilfield located in the central Gulf of Suez. Saturated hydrocarbon fractions were subjected to gas chromatography and gas chromatography–mass spectroscopy in order to characterize the type of organo-facies, oil classes and depositional environments, as well as, to assess the thermal maturity level for oil generation. The results showed that the studied oils are belonging to normal oils classes with no heavy biodegradation. Also, the crude oils are more mature and sources derived mainly from mixed organic sources from terrestrial and marine inputs contribution to the biomass from algae and plankton in different saline environments. 1