西北地区侏罗纪煤系有机质成烃模式  

The petroleum generation model for organic matterfrom Jurassic coal measure, Northwest China

作　　者：陈建平[1] 黄第藩[1] 李晋超 秦勇[2] 朱兴珊[3] 

机构地区：[1]中国石油天然气总公司石油勘探开发科学研究院,北京100083 [2]中国矿业大学,徐州221008 [3]山东矿业学院,泰安271000

出　　处：《地球化学》1999年第4期327-339,共13页Geochimica

基　　金：中国石油天然气总公司"八五"科技攻关项目!(编号:Z940101);山东省优秀青年科学家奖励基金

摘　　要：西北地区侏罗纪煤系地层中主要的生烃显微组分是孢子体、角质体、藻类体、沥青质体、碎屑类脂体、基质镜质体等，而树脂体、木栓质体等早期低熟生油组分含量很低。从煤中分离出来的一些主要单显微组分的热解模拟显示它们成烃演化特征基本相似， 主要生油窗在模拟温度３６０ ～４５０ ℃， 生油高峰在３９０ ～４２０ ℃， 分别相应于 Ｒｏ 约０ ．７ ％ ～１ ．２ ％ 和０ ．９５ ％ ～１ ．０％ 左右。显微荧光分析表明，镜质组反射率Ｒｏ 在约０ ．７ ％ 左右时，次生荧光大量出现，并随成熟度增加而逐渐增加，标志着大量生油的开始。煤中可溶有机质含量从泥炭阶段至烟煤阶段逐渐降低，并未显示转化率高峰，但烃类转化率高峰在Ｒｏ ０ ．８ ％ ～１ ．２ ％ 阶段。可溶有机质组分的变化也充分表明， 煤系有机质主要生排油时期是在Ｒｏ ＞ ０ ．７ ％ 时的成熟阶段。西北地区侏罗纪煤系含油气盆地中目前发现的油气一般分布于成熟烃源岩分布区及邻近地区。因此，侏罗纪煤系有机质成油模式是热降解成熟生油模式。Main macerals of hydrocarbon generation are sporinite, cutinite, alginite, bituminite, liptodetrinite and desmocollnite in source rocks from Jurassic coal measure in Northwest China. Subernite and resinite, regarded as macerals generating hydrocarbon in immature and lower mature, are extremely in low concentration. The pyrolysis simulation of concentrates of some dominant macerals isolated from Jurassic coals reveals that those macerals have similar characteristics in hydrocarbon generation, and that the pyrolysis temperature of the main oil generating window is in the range of about 360 ～ 450 ℃, and the temperature of the peak oil generation is about 390 ～ 420 ℃, being equal to vitrinite reflectance (Ro) about 0.7% to 1.2% and 0.95% respectively. Micro fluorescence analysis of the coals shows that large amount of secondary fluorescence occurs when vitrinite reflectance is about 0.7%, moreover, its intensity increases with the increase of maturity. It indicates that large number of oil begins to generate from organic matter. The content of extractable organic matter decreases from peat to meagre coal with the increase of maturity, but hydrocarbon transformation ratio presents a peak at about 1.0% vitrinite reflectance. The composition changes of the extractable organic matter (bitumen) in coals also indicate that large number of petroleum generation and migration take place at the mature stage of vitrinite reflectance beyond 0.7%. In generally,that oilfields have been discovered in Jurassic coal bearing basins in Northwest China near or around source rock, where the maturity of source rocks is generally greater than 0.7% vitrinite reflectance. In summary, all of the above evidence suggests that the oil generation model for organic matter in the Jurassic coal bearing basins in Northwest China is still thermal cracking in mature stage.

关 键 词：成烃模式 煤系 有机质 侏罗纪 显微组分 油矿床 

分 类 号：P618.130.1[天文地球—矿床学] P618.130.2[天文地球—地质学]