辽河断陷西部凹陷原油地球化学特征及其成因类型

THE GEOCHEMICAL CHARACTERISTIC AND GENETIC TYPE OF CRUDE OIL IN THE WESTERN SAG OF THE LIAOHE BASIN

辽河断陷西部凹陷原油物性和族组成具有由深到浅、由凹陷中心向边缘,原油密度、粘度及含蜡量等逐渐增加,饱和烃含量降低,非烃+沥青质含量增高的特征。从原油饱和烃色谱实验分析来看,色谱面貌既有单峰型,又有双峰型;既有前峰,又有后峰型;既有光滑,又有锯齿型;还有降解型。色谱参数Pr/Ph比值南部普遍较北部高。从饱和烃色质分析来看,原油甾烷系列C27—C29规则甾烷以直线斜坡型为主,凹陷南部少数以C28规则甾烷占优势。综合原油的物理性质及地球化学特征,将该区原油按生源与成油环境划分成2大类,再根据成熟度与遭受的次生改造作用,将这2大类各划分3个亚类。这种以微观实验数据为依托,综合原油宏观特征的分类方法将为今后的油源对比研究及勘探预测提供可靠的依据。

The physical property and group composition of the crude oil in the Western Sag, Liaohe Basin possess the characteristics, such as density, consistency and wax content increase, while saturated hy- drocarbon content decrease and nonhydrocarbon and asphaltene content increase along with the oil from deep to shallow layer, from center to boundary of the sag. Saturated hydrocarbon has various spectrums, such as single peak and double peak, front and queen, smoothing and serration, as well as biodegradation. The rate of Pr/Ph in the south is higher than the north. The distribution of C27 --C29 regular sterane is dominated by right line ramp type, and only few samples have higher C28 content in the south. Summing up the physical property and geochemical behavior, the crude oil are divided into two types based on biologic source and sedimentary environment, then divide these two types into three subtypes based on maturity and biodegradation. The results will provide dependable foundation to correlation of oil--source rock and exploration.