Use of light hydrocarbons for the oil-oil correlation in Pearl River Mouth Basin, South China Sea

Abstract

The composition of 28 oil samples from Wenchang and Enping formations of Pearl River Mouth Basin (PRMB) was characterized and emphasis was placed on compositional variations in the gasoline range (i-C5H12-n-C8H18). The light hydrocarbons (LHs) were sensitively determined by gas purge microsyringe extraction (GP-MSE) coupled with gas chromatography-mass spectrometry (GC–MS) and GC-flame ionization detector (FID), respectively. According to the relative concentration of LHs, the Mango’s K1 parameter was calculated and a cross plot was obtained. Invariance in the K1 ratio was observed with a correlation coefficient approximately equal to 1 for all the studied crude oils, however, the absolute K1 values were different for each oil family, which indicates the distinct genetic features. Furthermore, several LH indicators were screened and a model was developed for correlating oils using LHs combined with multivariate statistical method. To validate the model, the correlation results based on routine biomarkers and LHs were compared by using normal oil samples, and consistent conclusions were achieved. As alternative to routine biomarkers, LHs show good potential in geochemical correlation of crude oils, especially when routine biomarkers are absent or at very low concentration in high maturated oil samples.