Biogeochemical Analyses of Four Crude Oil Samples to Confirm the Presence of Terrestrial-organic Matter, Collected from the Murzuq Basin- Libya

Abstract

The Murzuq Basin, in Southwestern Libya, is one of Libyan’s most productive petroleum basins, with reserves estimated at 23 billion barrels recoverable of hydrocarbon equivalent within giant oil fields. Four crude oil samples collected from A1-NC186, E1-NC101, E2-NC101, H10-NC115 wells from Murzuq Basin, Libya, were suggested for bulk analysis and physical proprieties, alkane distribution and isoprenoids and the hopane, tricyclic terpane and sterane distributions of the oils, to confirm the presence of non-marine organic matter sources and/or any evidence of its existence. The oils show no significant variation in the ratios of the carbon, hydrogen, nitrogen and sulfur content (CHNS) composition. All samples recorded high to very high API° gravity, ranges 33.8 to 40.3; the sulfur values ranged from 0.31 to 0.45%, the wax ratio in crude oils is showing a great variety, E1-NC101and E2-NC101 oils show higher wax content, ranging from 6.1 to 6.7%. Pristine to Phytane ratios (Pr/Ph) range from 1.61 to 2.22 and the Pr/n-C17, Ph/n-C18, n-C17/n-C27 and CPI values determined as indicators of the depositional environment of the crude oils. The data of search confirmed that the crude oils were derived from marine, mixed and terrestrial sediments.