scholarly journals Saturated biomarkers in the estimation of organic geochemical homogeneity of crude oils from four oil fields in Libya

2020 ◽  
Vol 85 (11) ◽  
pp. 1489-1499
Author(s):  
Ramadan Saheed ◽  
Tatjana Solevic-Knudsen ◽  
Musbah Faraj ◽  
Zlatko Nikolovski ◽  
Hans Nytoft ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Organic Matter ◽  
Relative Concentration ◽  
Oil Fields ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Crude Oils ◽  
Terrestrial Organic Matter ◽  
Migration Pathways

Seven crude oils from four oil fields in the Sirte and Murzuq Basins in Libya were investigated in order to estimate their organic geochemical homogeneity. Saturated biomarkers (n-alkanes and isoprenoids) were analyzed using gas chromatography?mass spectrometry (GC?MS). The parameters calculated from the distributions of n-alkanes and isoprenoid aliphatic alkanes, pristane and phytane were used to interpret the organic geochemical characteristics of the oils. Based on the high relative concentration of lower n-alkane homologues in the C11?C16 range and high API values, the oils were classified as light oils. These results also implied that the oils were not biodegraded. The parameters calculated from the distributions of saturated biomarkers indicated that all investigated oils were generated from source rocks containing organic matter of a similar marine origin but with a contribution of terrestrial organic matter. The results also demonstrated that these source rocks were deposited in an oxic environment. The same source rock or the same type of source rocks for all seven samples were postulated. It was concluded that, if the crude oils from these distant basins originated from the same source rocks, they must have had different lengths of their migration pathways.

scholarly journals GC-MS vs. GC-MS-MS analysis of pentacyclic terpanes in crude oils from Libya and Serbia - a comparison of two methods

2017 ◽  
Vol 82 (11) ◽  
pp. 1315-1331 ◽  
Author(s):  
Musbah Faraj ◽  
Tatjana Solevic-Knudsen ◽  
Ksenija Stojanovic ◽  
Sonja Ivkovic-Pavlovic ◽  
Hans Nytoft ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Oil Field ◽  
Oil Fields ◽  
Gas Chromatography Mass Spectrometry ◽  
Crude Oils ◽  
Chromatography Mass Spectrometry ◽  
Almost All ◽  
Parameter Values ◽  
H 30

The values of parameters calculated from distribution and abundance of the selected pentacyclic terpanes in crude oils from Libya and Serbia, which were originally derived from gas chromatography-mass spectrometry (GC?MS) were compared with results of quantification based on gas chromatography? ?mass spectrometry-mass spectrometry (GC?MS-MS). The parameters analyzed are the most often used terpane source and maturity parameters, which were applied to a large sample set of 70 oils, originating from five oil fields. The aim of the paper was to investigate to which extent the measurements of the selected parameters by these two instrumental techniques agree and to determine the influence of differences between parameter values on geochemical interpretation. For that purpose two methods, concordance correlation coefficient and mean-difference plot were used. The obtained results indicate that calculation of C2718?(H)-22,29,30-trisnorneohopane/(C2718?(H)-22,29,30- -trisnorneohopane + C2717?(H)-22,29,30-trisnorhopane), C2918?(H)-30-norneohopane/ C2917?(H)21?(H)-30-norhopane and C2917?(H)21?(H)-30-norhopane/ C3017?(H)21?(H)-hopane ratios either by GC?MS or GC?MS-MS do not significantly influence interpretation. On the other hand, the determination of C3017?(H)21?(H)-moretane/C3017?(H)21?(H)-hopane ratio, gammacerane index and oleanane index by GC?MS vs. GC-MS-MS could notably affect interpretation. These differences can be explained by the co-elution and the peak overlapping in GC?MS but also by better separation, higher precision and better selectivity of the GC?MS-MS. Deviation of the almost all studied parameters from the line of equality was similar for the oils from the same oil field but some differences were observed for the oils from different oil fields. Therefore, when GC?MS-MS results are to be used in organic geochemical interpretations, a regional calibration of GC?MS vs. GC-MS-MS relationship for each petroleum system is highly recommended.

scholarly journals Petrography and Organic Geochemistry Characterizations of Lower Paleozoic Organic-Rich Shale in the Northwestern Upper Yangtze Plate: Niutitang Formation and Longmaxi Formation, Dabashan Foreland Belt

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 439 ◽  
Author(s):  
Delu Li ◽  
Rongxi Li ◽  
Di Zhao ◽  
Feng Xu
Keyword(s):  
Gas Chromatography ◽  
Organic Matter ◽  
Organic Geochemistry ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Mature Stage ◽  
Type I ◽  
Lower Paleozoic ◽  
Longmaxi Formation ◽  
Niutitang Formation

Measurements of total organic carbon, Rock-Eval pyrolysis, X-ray diffraction, scanning electron microscope, maceral examination, gas chromatography, and gas chromatography-mass spectrometry were conducted on the organic-rich shale of Lower Paleozoic Niutitang Formation and Longmaxi Formation in Dabashan foreland belt to discuss the organic matter characteristic, organic matter origin, redox condition, and salinity. The results indicate that the Niutiang Formation and Longmaxi Formation organic-rich shale are good and very good source rocks with Type I kerogen. Both of the shales have reached mature stage for generating gas. Biomarker analyses indicate that the organic matter origin of Niutitang Formation and Longmaxi Formation organic-rich shale are all derived from the lower bacteria and algae, and the organic matter are all suffered different biodegradation degrees. During Niutitang Formation and Longmaxi Formation period, the redox conditions are both anoxic with no stratification and the sedimentary water is normal marine water.

Sign in / Sign up

Export Citation Format

Share Document