Geochemical Characteristics of Six Formations Based on Organic Geochemical Parameters, Murzuq Basin, Libya

Abstract

Cutting samples (n = 150) and Core samples (n = 6) from the Taouratine, Dembaba, Assedjefar Marar, Awaynat Wanin, Tanezzuft and Mamuniyat Formations ( Jurassic to Ordovician), derived from wells (A-3, B-1, H-1 and H-15), locate in the A, B and H fields, present in Murzuq Basin were analysed. Rock-Eval Pyrolysis, Total Organic Carbon and specific Aromatic Molecular Biomarker (by the use of chromatography- mass spectrometry GC-MS) as geochemical parameters implemented to investigate their Lithology, kerogen type, organic matter (OM) richness and maturity evaluation. Such Formations are fair to very good quantity of organic matter passing in the course of excellent source rocks, have average of organic carbon richness (TOC) value ranged between  0.2% to 16.7% with one anomalously rich sample at 666m (well H-1) where a dark grey shale has a TOC content of 46.1% and high potential yield over 90000 ppm. The studied rocks are ranged from immature to mature of hydrogen index (HI) ranged between 24 - 302 mg HC/g TOC versus pyrolysis Tmax, with dominance of kerogen II/III Type, resulted  based on HI versus oxygen index (OI), ranged from 3 to 161 mg CO2/g TOC. The Tmax , spore colouration (SCI)  and Vitrinite Reflectance (% Ro) as maturity parameters ranged among  425 - 445, 5 - 8.5 and 0.35 - 3 respectively. Aromatic hydrocarbon ratios by use of gas chromatography - mass spectrometry pointed to two levels of thermal maturity, where the high level of thermal maturity recorded in lower Silurian, whereas the less maturity was from other formations.