Biomarker characteristics in hydrocarbon source rocks of Hongqi Formation, Tuquan Basin

Based on gas chromatography mass spectrometry techniques, the biomarker characteristics of the Hongqi Formation source rocks in the Tuquan basin are studied, information and petroleum geological significance on organic matter origin, sedimentary environment and organic matter maturity are revealed. Biomarker assemblage characteristics of the Hongqi Formation source rocks are described as follows: Long-chain tricyclic terpane and gammacerane is abundant, C-27 regular steranes is predominant. The low content of gammacerane in organic matter shows that the source rocks were deposited in the low salinity environment. The mean value of steranes/hopanes is 0.40, showing more contribution from algae than bacteria. High content of C27 regular steranes indicate that the parent material input is mainly the low aquatic organism. Biomarker parameters including Ts/(Ts+Tm) ratio, C-29 steranes 20S/(20S+20R) ratio, C-29 sterane alpha beta beta/(alpha beta beta+alpha alpha alpha) ratio indicate that Hongqi Formation source rock has reached or surpassed the main phase of oil generation.