摘要
库车坳陷的烃源岩主要发育在中上三叠统和中下侏罗统,根据烃源岩厚度和有机相特征、埋藏热历史,采用BasinMod-1D软件,系统分析了库车坳陷上三叠统和中下侏罗统气源灶的生气强度及其在地质历史中的演化。中上三叠统气源灶以克拉苏构造带为生气中心,向四周生气强度逐渐变小;中下侏罗统气源灶则以拜城凹陷和依奇克里克构造带为中心,向南北两端生气强度逐渐变小。无论是上三叠统还是中下侏罗统气源灶,现今累计生气强度在坳陷主体均在20×108m3/km2以上,生气中心则在(60～100)×108m3/km2。上三叠统气源灶的大量生气始于12Ma,中下侏罗统气源灶大量生气则始于5Ma,库车坳陷气源灶演化的特色表现在5Ma以来气源灶极高的生气速率。中上三叠统源岩生气强度类似于中下侏罗统,说明中上三叠统源岩对天然气成藏的贡献不亚于中下侏罗统源岩,库车坳陷气源灶存在充足的气源且近5Ma快速生气,这是库车坳陷形成高效天然气藏的重要原因,库车坳陷目前发现的大中型气田(藏)均分布在生气中心及其周缘。
The Middle-Upper Triassic and Lower-Middle Jurassic gas-prone source rocks are two sets of gas source rocks of the Kuqa depression, Tarim basin. According to geological and geochemical data of source rocks （including thickness, TOC, organic facies, burial and thermal history, etc）, the gas generation history of these two sets of source rocks are reconstructed and modeled using BasinMod-lD. The gas generation center of the Middle-Upper Triassic gas kitchen lies in the Kelasu structural zone, gas generation intensity decreased far from the center. The gas generation centers of the Middle and Lower Jurassic gas kitchen lie in the Baicheng sag and the Yiqikelike structural zone, less gas was generated southward and northward. Whether the Middle-Upper Triassic or the Middle and Lower Jurassic gas kitchen, the present cumulative gas generation intensity of the hydrocarbon kitchen is above 2 000 ×10^6m^3/km^2, and ranges from 6 000 ×10^6m^3/km^2 to 10 000 ×10^6 m^3/km^2 in the central areas of hydrocarbon kitchen. The main gas generation stage began in 12 Ma and 5 Ma for Middle-Upper Triassic hydrocarbon kitchen and the Middle-Lower Jurassic hydrocarbon kitchen, respectively. The two gas kitchens of Kuqa are characterized by very high gas generation rate in recent 5 Ma. The gas generation intensity of the Middle-Upper Triassic hydrocarbon kitchen was similar to that of the Lower-Middle Jurassic one, which implies that gas originated from Middle-Upper Triassic source rock may play an important role in gas accumulation just like gas originated from Lower-Middle Jurassic hydrocarbon kitchen. The two key geological factors for the formation of giant effective gas fields in Kuqa depression are sufficient gas source and rapid gas generation in recent 5 Ma. The main gas reservoirs or gas fields presently discovered are distributed in or near the gas generation center.
出处
《地球化学》
CAS
CSCD
北大核心
2006年第4期419-431,共13页
Geochimica
基金
国家重点基础研究发展计划项目(2003CB214603)
国家重点科技攻关项目(99-111-01-03)
关键词
气源灶
生气强度
生烃史
库车坳陷
塔里木盆地
hydrocarbon kitchen
gas generation intensity
gas generation history
Kuqa depression
Tarim basin
