Non-cracked oil in ultra-deep high-temperature reservoirs in the Tarim basin, China
Non-cracked oil in ultra-deep high-temperature reservoirs in the Tarim basin, China
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DOI：
10.1016/j.marpetgeo.2017.07.019
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发表时间：
2018
影响因子：
4.2
通讯作者：
G. Zhu;A. Milkov;Feiran Chen;N. Weng;Zhiyao Zhang;Haijun Yang;Keyu Liu;Yongfeng Zhu
中科院分区：
文献类型：
--
作者：
G. Zhu;A. Milkov;Feiran Chen;N. Weng;Zhiyao Zhang;Haijun Yang;Keyu Liu;Yongfeng Zhu
地下液态石油的热稳定性与储集层温度密切相关。大多数石油聚集发生在&120℃的温度下，石油在&150-160℃的温度下裂解成气，导致天然气凝析油和游离气聚集在超深高温储层中占主导地位。最近钻探的富源1号探井(塔里木盆地北部)从最深7711米、温度172℃的碳酸盐岩储层中开采出优质的不裂解单相(黑色)石油，这是中国迄今发现的最深的石油，也是世界上发现的最深的石油之一。原油密度(20℃或api重力40°时为0.825 g/cm3)、相对较低的气油比(135g/m3或758scf/bbl)、金刚烷种类和丰度较低以及缺乏硫金刚烷和二苯并噻吩类化合物，表明原油是在中等热成熟度时从源岩中排出的，没有被裂解。石油伴生气体的分子和同位素组成与这一解释一致。我们认为，石油仍然没有裂解，因为在>；150-160°C温度下的停留时间相对较短(<；5My基于一维模型)，显然不足以裂解。我们认为，在塔里木盆地和世界各地其他地温梯度较低、埋藏时间较晚的高温油气藏中，仍有可能发现未蚀变的液态石油。
Thermal stability of liquid petroleum in the subsurface is closely linked to reservoir temperature. Most oil accumulations occur at temperatures <120 °C. Oil cracks into gas at temperatures >150–160 °C leading to the dominance of gas condensate and free gas accumulations in ultra-deep high-temperature reservoirs. The recently drilled Fuyuan-1 exploration well (northern Tarim basin) produced high-quality non-cracked single-phase (black) oil from a carbonate reservoir located at maximum depth 7711 m and temperature 172 °C. This is the deepest oil discovery in China to date and among the deepest in the world. The oil density (0.825 g/cm3at 20 °C or API gravity 40°), relatively low gas/oil ratio (135 m3/m3or 758 scf/bbl), low variety and abundance of adamantanes as well as lack of thiaadamantanes and dibenzothiophenes indicate that the oil was expelled from a source rock at moderate thermal maturity and has not been cracked. The molecular and isotopic composition of oil-associated gases are consistent with this interpretation. We suggest that the oil remained uncracked because the residence time at temperatures >150-160°C was relatively short (<5 my based on 1D modeling) and apparently insufficient for cracking. We conclude that there is potential for finding unaltered liquid petroleum in other high-temperature reservoirs with relatively low geothermal gradient and recent burial in the Tarim basin and around the world.