辽西牛营子凹陷北票组烃源岩生物标志化合物特征——以辽凌地1井为例

采用气相色谱、气相色谱-质谱技术,研究了辽西牛营子凹陷辽凌地1井1527.91~1722.78 m(未见底)北票组烃源岩的生物标志化合物特征,剖析其沉积环境、有机质生源、有机质热演化程度等方面的信息. 牛营子凹陷北票组烃源岩样品的正构烷烃相关参数间接表征烃源岩成熟度较低,多为未成熟-低成熟阶段;有机质输入以陆源输入为主,有部分低等生物输入; Pr/Ph值主要介于0.94~5.01之间,平均为3.40,具有典型煤系地层有机质特征,形成于偏氧化性环境; C₂₄TeT/C₂₆TT-(C₂₀ +C₂₁)TT/(C₂₃+C₂₄)TT值整体偏高,指示一种高等植物来源; C₂₄-四环二萜/C₂₆三环萜烷比值分布于1.15~5.28,平均值为2.76,表明其陆源高等植物贡献较为充足;伽马蜡烷指数分布在0~0.04,平均值为0.02,反映当时的沉积环境为淡水环境;在m/z217质量色谱图中样品甾烷呈现C₂₉甾烷占优势的反"L"型,表示为高等植物输入占绝对优势. 综合研究认为牛营子凹陷北票组烃源岩形成于淡水的偏氧化性环境,具有典型煤系地层有机质特征,有机质来源为陆源高等植物贡献,具有油气勘探前景.

BIOMARKER CHARACTERISTICS OF THE SOURCE ROCKS OF BEIPIAO FORMATION IN NIUYINGZI SAG,WESTERN LIAONING: A Case Study of LLD1 Well

By using gas chromatography and gas chromatography-mass spectrometry, the paper studies the biomarker compound characteristics of Beipiao Formation source rocks from LLD1 well at the depth of 1527.91-1722.78 m (bottom unreached) in Niuyingzi sag of western Liaoning, and analyzes the sedimentary environment, source and thermal evaluation degree of organic matter. The n-alkane relative parameters of source rock samples indirectly indicate that the maturity of source rocks is low, mostly in immature-low mature stage. The organic input is mainly terrestrial source, with some lower organisms. The Pr/Ph ratio is 0.94-5.01, averagely 3.40, with the characteristics of organic matter in typical coal measure strata, formed in oxidizing environment. The C₂₄TeT/C₂₆TT-(C₂₀+C₂₁)TT/(C₂₃+C₂₄)TT value is generally high, indicating the source of higher plants. The C₂₄-tetracyclic diterpene/C₂₆ tricyclic terpane ratio is 1.15-5.28, averagely 2.76, reflecting that the terrestrial higher plants contribute a lot. The gammacerane index of 0-0.04, averagely 0.02, show a freshwater sedimentary environment. The sterane in source rock samples, showing an inverse L-shape with dominant C₂₉ sterane in the m/z217 gas chromatogram, indicates that the higher plant input is absolutely dominant. From the above study, it is considered that the Beipiao Formation source rocks in Niuyingzi sag were formed in the oxidizing environment of freshwater, with the characteristics of organic matter in typical coal measure strata. The organic matter is derived from terrestrial higher plants, which has oil-gas exploration prospect.