松辽盆地滨北西部上二叠统林西组烃源岩生物标志化合物的特征及意义

应用气相色谱、气相色谱-质谱技术，研究了滨北西部上二叠统林西组烃源岩的生物标志化合物特征，对烃源岩有机质来源、沉积环境、热演化程度等进行了分析.研究表明，林西组烃源岩有机质丰度高，有机质类型为Ⅱ型，处于高成熟-过成熟演化阶段；烃源岩中（C₂₀+C₂₁）/（C₂₃+C₂₄）三环萜烷为0.12~0.86，平均为0.50，C₂₄四环萜烷/C₂₆三环萜烷为0.41~0.72，平均为0.54，具有典型湖相烃源岩特征；Pr/Ph主要介于0.16~0.71之间，平均为0.32，指示沉积环境为强还原-还原环境；伽马蜡烷/C₃₀藿烷为0.09~0.35，平均为0.21，反映烃源岩为半咸水的沉积环境；Pr/nC₁₇与Ph/nC₁₈的关系、C₂₇-C₂₈-C₂₉甾烷的相互关系均反映有机质为高等植物和细菌、藻类等低等水生生物的混合来源；Ts/Tm为0.18~1.03，平均为0.86，C₃₁αβ22S/（22S+22R）比值为0.53~0.62，平均为0.58，均指示烃源岩成熟度较高.综合认为林西组烃源岩形成于半咸水的还原-强还原环境，有机质来源为混合来源，有利于有机质的富集，林西组具有油气勘探前景.

BIOMARKER COMPOUNDS IN THE SOURCE ROCKS OF UPPER PERMIAN LINXI FORMATION IN WESTERN BINBEI AREA,SONGLIAO BASIN: Characteristics and Implications

The characteristics of biomarker compounds in the source rocks of Upper Permian Linxi Formation are studied, as well as the sources, sedimentary environment and thermal evolution degree of organic matter, based on the gas chromatography and gas chromatography-mass spectrometry. The results show that the source rocks, with organic matter Type II, have high organic abundance in the high mature-overmature evolution stage. The (C₂₀+C₂₁)/(C₂₃+C₂₄) tricyclic terpane is 0.12-0.86 (averagely 0.50). The C₂₄ tetracyclic terpene/C₂₆ tricyclic terpene is 0.41-0.72 (averagely 0.54), with the characteristics of typical lacustrine source rocks. The Pr/Ph is mainly 0.16-0.71 (averagely 0.32), indicating a strong reduction-reduction sedimentary environment. The gammacerane/C₃₀ hopane is 0.09-0.35 (averagely 0.21), reflecting the brackish water sedimentary environment. The relation between Pr/nC₁₇ and Ph/nC₁₈, and interrelation of C₂₇-C₂₈-C₂₉ steranes show that the organic matters are the mixed sources of higher plants with lower aquatic organisms like bacteria and algae. The Ts/Tm ratio of 0.18-1.03 (averagely 0.86) and C₃₁αβ22S/(22S+22R) ratio of 0.53-0.62 (averagely 0.58) both show the source rock maturity is high. From the above, it is concluded that the source rocks were formed in the reduction-strong reduction environment of brackish water, and the mixed sources are favorable for the enrichment of organic matters, thus the Linxi Formation has oil-gas exploration prospects.