塔里木盆地中上奥陶统碳酸盐岩烃源岩沉积环境

Sedimentary Environment of Carbonate Source Rocks of Middle-Upper Ordovician in Tarim Basin

塔里木盆地中上奥陶统碳酸盐岩烃源岩在同一时期不同的沉积环境(台缘斜坡、台地内凹陷、陆棚、深海盆地等)中均有发育。根据沉积相带与沉积环境的不同,可将烃源岩划分为在不同沉积环境中发育的4种类型烃源岩:台地边缘灰泥丘型烃源岩、台地内凹陷型烃源岩、深水缓坡与陆棚型烃源岩、深海盆地型烃源岩。灰泥丘型烃源岩发育在上奥陶统台地边缘带,其他3种类型烃源岩在寒武-奥陶系均有分布。分析中上奥陶统烃源岩沉积环境,重要的是寻找碳酸盐岩台地边缘、台地内凹陷边缘,从而能够确定台缘斜坡、台地内凹陷、陆棚等烃源岩沉积环境。通过在地震剖面中识别台地边缘,并结合识别生物礁丘的发育位置,可最终确定台地边缘、台内凹陷边缘带,因此,从某种意义上说,生物礁的分布对烃源岩的分布具有重要的指示意义。

The carbonate source rocks of Middle-Upper Ordovieian in Tarim basin are widely distributed in different sedimentary environments at the same period such as platform margin slope, platform inner sag, continental shelf, abyssal basin, etc. According to the differences of sedimentary facies and environment, the source rock are divided into four types such as lime-mud reef in platform margin, platform inner sag, deep-water fiat slope or continental shelf, abyssal basin. The lime-mud reef type is distributed in platform margin of Upper Ordovician, the remained three types are widely distributed in Cambrian-Ordovician system. The carbonate platform margin and platform inner sag margin could be recognized from analysis of sedimentary environment of the Middle-Upper Ordovician source rocks for the purpose of determination of the sedimentary environments of source rocks of platform slope, platform inner sag and continental shelf. In addition, by means of seismic profiles, the platform margin and the platform inner sag margin can be finally identified, integrated with distribution of organic reefs. It is shown that the distribution of organic reefs is of great significance in indicating the distribution of source roeks.