塔里木盆地顺北地区奥陶系超深层原油金刚烷化合物分布及意义

塔里木盆地顺北地区奥陶系超深层一间房组—鹰山组获得了工业油气产能,不同断裂带油气相态存在差异。使用色谱-质谱、色谱×色谱-飞行时间质谱方法研究了顺北地区原油中金刚烷的分布及含量。顺北地区奥陶系原油金刚烷组成中,1号断裂带(分支断裂、次级断裂)和3号断裂带原油单金刚烷相对含量高于5号断裂带和7号断裂带原油。顺北地区原油金刚烷总量与4-甲基二苯并噻吩/1-甲基二苯并噻吩值之间呈现正相关关系,表明成熟度决定了原油中金刚烷总量。不同断裂带原油中单金刚烷系列、双金刚烷系列相对比例的不同与油气藏多期成藏及油气藏保存条件不同有关。1号断裂带油气藏喜马拉雅晚期较高成熟度天然气的充注,从深部携带了较高比例的单金刚烷系列,造成原油单金刚烷系列含量相对较高。5号断裂带油气藏保存条件逊色于1号断裂带油气藏,轻质组分不同程度损失,导致原油中单金刚烷比例较低。由于金刚烷内组成含量的差异,分别使用22μg/g、33μg/g作为1号断裂带、5号断裂带原油中甲基双金刚烷基线,1号断裂带(含分支、次级断裂带)、5号断裂带中段及5号断裂带南段原油裂解比例分别为0~42%、20%~33%和54%。

Characteristics of diamondoids in oils from the ultra-deep Ordovician in the North Shuntuoguole area in Tarim Basin,NW China

Industrial oil&gas production was obtained in the ultra-deep Ordovician Yijianfang to Yingshan formations from North Shuntuoguole area in Tarim Basin,NW China.The reservoir phases varied among different faults.Using the GG-MS and GC×GC-TOFMS methods,the study focused on the distribution and concentrations of diamondoids of the Ordovician oil in the North Shuntuoguole area.In the relative content of diamonoids,oil samples from No.1(including splay and sub-faults)and No.3 faults have higher contents of adamantanes than that of the oils from No.5 and No.7 faults.The concentrations of diamondoids of oil samples from the North Shuntuoguole area showed positive correlation with the 4-/1-MDBT ratio,suggesting that the concentrations of diamondoids of oil samples were controlled by the maturity.The difference of the relative content of adamantanes and diamantanes of oil samples from the different faults may be related to the multiple hydrocarbon filling history and the different preservation condition.The reservoirs of No.1 fault were charged with the natural gas with relative higher maturity in late Himalayan,receiving more content of admanantanes from the deep strata and leading to the enrichment of adamantanes in oils.The preservation condition of the reservoirs from No.5 fault were inferior to that of the No.1 faults,represented by the loss of the light hydrocarbon to some degree,and resulted in the decrease of adamantanes in oil samples from No.5 fault.Because of the difference in the relative contents of diamondoids,the(4-+3-)methyldiamantane concentrations of 22μg/g and 33μg/g were used as the baseline values for the oil samples from No.1 and No.5 faults,respectively.Using the method proposed by Dahl et al,the degree of oil-cracking of the oil samples from the No.1 fault(including sub-fault and splay fault),the middle part and the south part of No.5 fault are 0-42%,20%-33%and 54%,respectively.