A Novel C7-Based Star Diagram Applied on Oil-Oil Correlations From the Pearl River Mouth Basin, Southeastern China

Abstract

We proposed a new star diagram, which consists of eight ratios composed of compounds that are very resistant to the effects of transformation, and thus are useful for correlation, the eight ratios are 2,2-dimethylpentane/P3, 2,3-dimethylpentane/P3, 2,4-dimehtylpentane/P3, 3,3-dimethylpentane/P3, 2-methylpentane/P3, 3-mehtylpentane/P3, 2-methylhexane/P3 and 3-methylhexane/P3 respectively (P3 is the sum of the eight members). This diagram can be used to correlate both transformed and primary oils based on source-relate chemical differences. To carry out this project, we creatively changed the configuration of the columns in the GC-FID. Compared with the previous column configuration, two columns were perfectly coupled and so the total length of the columns was added to 110m. The results show that two pairs of key compounds, benzene and cyclohexane, methylcyclopentane and 2,4-dimethylpentane, were successfully separated, which usually fail in traditional methods. The most exciting thing is that a new fingerprint parameter of light hydrocarbon related to 1,1-dimethylcyclopentane is firstly obtained. In this study, 49 oil samples from Pearl River Mouth Basin were analyzed by using gas chromatography with flame ionization detector (GC-FID), GC with mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS), respectively. Firstly, compounds in gasoline range (i-C5H12-n-C8H18) were identified and quantified by directly injecting the oil samples to GC-FID. Five standard samples, i.e hexane, 2,4-dimethylpentane, benzene, cyclohexane and toluene, were injected into GC-FID to validate the identification of the gasoline range hydrocarbons. Secondly, the oil samples were further analyzed by GC-MS and GC×GC-TOFMS, and more than 300 compounds were identified and quantified, including terpenes, steranes, aromatic hydrocarbons, polyaromatic hydrocarbons, and heteroaromatic sulfur-, oxygen-, and nitrogen-containing compounds. We firstly apply this star diagram on oils from the Pearl River Mouth Basin for oil-oil correlations, and divide them into families A, B and C. To validate the classification, we apply some common-used biomarker parameters on oil-oil correlations, including terpenes, steranes, benzothiophenes, isoparaffin and N-alkanes etc, and the same conclusion was obtained, which provide reliable evidence for the oil-gas exploration from Pearl River Mouth Basin.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015