ISSN: 2319-8753 International Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization) Vol. 3, Issue 9, Setember 2014 DOI: 10.15680/IJIRSET.2014.0309079 Copyright to IJIRSET www.ijirset.com 16359 Gas Chromatography-Mass Spectroscopy for Determining Biomarkers in Crude Oils Ashraf Yehia El-Naggar Department of Chemistry, Faculty of Science, Taif University, Kingdom of Saudi Arabia Egyptian Petroleum Research Institute, Nasr City, Cairo, Egypt ABSTRACT: Four crude oil samples recovered from some producing wells in the southern part of the Egyptian Gulf of Suez were subjected for measuring some organic geochemical parameters. Biomarkers are biological markers such as Terpanes and steranes of the saturated hydrocarbons obtained by gas chromatography-mass spectorometry (GC-MS). In addition to n-alkanes and isoprenoids distributions obtained by gas chromatography (GC). Terpanes biomarker distributions ( m/z 191) mass chromatograms for oil samples is revealing marine organic facies of depositional environmental and maturation parameter. Hopane distributions (m/z = 191) indicates the marine organic sources. The steranes distributions for the oil samples (m/z 217) suggest a pre Tertiary source rocks for these oil samples. KEY WORDS:- Crude oil, Organic geochemical parameters, Biomarkers, Terpanes, steranes, Depositional environmental, Maturation. I. INTRODUCTION Petroleum geochemistry is concerned with the application of chemical principals to study origin of organic matter, migration, alteration, and classification of crude petroleum. Various crude oil classifications have been proposed by geochemists and petroleum refiners. Geologists and geochemists are more interested in identifying and characterizing the crude oils, to relate them to specific source rocks and to measure their grade of maturation [1, 2]. Previous geochemical studies throughout the Gulf of Suez have revealed that the oils are derived mainly from marine sources which may be differentiated into three main groups, designated as I, II and III groups. The distribution of these oil families is consistent with the geographic subdivisions of the Gulf of Suez provinces in the northern, the central and southern. Group I oils are confined to the northern province of the Gulf of Suez and characterized by a C 33 /C 34 homohopane index <1 and a relatively heavy carbon isotope composition (δ13C saturated -27 %), suggesting generation from a less reducing marine source rock environment at relatively low levels of thermal maturity. Group II oils are confined to the central Gulf province and are characterized by low API gravity, a predominance of pristane over phytane, a high C 33 /C 34 homohopane index and a lighter carbon isotope composition (δ13C saturated -29 %) [3, 4]. Group III oils are located in the southern province and characterized by high API gravity, a low sulfur content and intermediate carbon isotope composition (δ13C saturated -28 to 29 %). This group of oils is believed to be derived from a marine source and exhibits compositional heterogeneity suggesting the presence of a complex petroleum system in the southern Gulf of Suez province. II. MATERIAL AND METHODS Samples Four crude oil samples were collected from wells of El Hamd oil field locates in the central Gulf of Suez, namely: H-1, H-2, H-3 and H-4.These samples are representative for the producing horizon zones of Middle-Lower Miocene age characterized by limestone facies with depths range from 754- 881m. (Top perforation), and 955- 1180m (Bottom of perforation). Crude oil fractionation The selected crude oil samples were distilled up to 200°C at atmospheric pressure in order to separate the heavy oil fractions above 200°C. These residual fractions were deasphalted according to IP-143 standard procedure. The maltene