Comparative study on distribution and composition of various biomarkers in crude oil from the oil fields of Qigequan and Xianshuiquan indicates the crude oil in the Qigequan oilfield has the integrated and abundant n-alkane serial, but the normal alkanes in the oil of the Xianshuiquan oilfield were partly biodegraded, resulting in the higher ratios of Pr/nC17 and Ph/nC18. The phytane preference in the crude oil from both oilfields and the less ratios of Pr/Ph in the Qigequan oil indicate that they were derived from the source rocks deposited in strong reducing environment. In the C27 C29 sterane serial, the ratio of C27/C29 is more than 1.0 in the Qigequan oil, while the ratio is about 0.8 in Xianshuiquan oil, suggesting that the contribution of algae plankton to oil in the Qigequan oilfield is more than that in the Xianshuiquan oilfield. The ratios of ααα20S/（ααα20S＋ααα20R）for C29 sterane and diadrimane abundance in the Xianshuiquan oil are more than that in the Qigequan oil, inferring that the thermal maturity of the Xianshuiquan oil is higher than that of the Qigequan oil. The integrated distribution of hopane serial in both oilfields exists, with high abundance of gammacerane. By comparision of abundance of long chain hopane and gammacerane in the oilfield of Xianshuiquan and Qigequan, we find that abundance of long-chain hopane and gammacerane in the former oil is lower than that in the later, indicating that the source rock of oil from the Qigequan oilfield was deposited under higher salinity and stronger reducing environment.
Natural Gas Geoscience