Compound-specific sulfur isotope analysis of thiadiamondoids of oils from the Smackover Formation, USA
Compound-specific sulfur isotope analysis of thiadiamondoids of oils from the Smackover Formation, USA
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DOI：
10.1016/j.gca.2015.07.008
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发表时间：
2015-10-15
影响因子：
5
通讯作者：
Amrani, Alon
中科院分区：
文献类型：
--
作者：
Gvirtzman, Zvi;Said-Ahmad, Ward;Amrani, Alon
硫杂环金刚烷类化合物（英语：Thiadiamondoid，TD）是一种在笼状结构中含有硫键的类金刚石化合物。这些化合物被认为是热化学硫酸盐还原（TSR）的发生和程度的分子代理。TD的化合物特定硫同位素分析可以创建多参数系统，基于分子和δ S-34值，其可以在更宽范围的TSR和热成熟阶段上敏感。在这项研究中，我们分析了一套12个上侏罗统的石油和凝析油样品产生的源岩在Smackover组进行系统的硫同位素分布在thiadiamondoids（一个和两个笼子）的研究。为了进行比较，我们测量了苯并噻吩（BT）和二苯并噻吩（DBT）的delta S-34组成。我们还进行了石油和模型化合物的热解实验，以深入了解TD的形成机制。根据TSR蚀变程度，不同油之间TD的S-34变化很大（约为千分之30）。结果表明，同一原油中，单笼TDs相对均匀，S-34富集值与共存BTs相似。双笼TD的δ S-34值变化更大，范围从BT的δ S-34值到DBT的δ S-34值，但相对于单笼TD，S-34普遍耗竭。用CaSO 4或元素S（当量S摩尔浓度）和金刚烷作为模型化合物的含水热解实验（360 ℃，40 h）证明了以相对低的产率形成单笼TD（
Thiadiamondoids (TDs) are diamond-like compounds with a sulfide bond located within the cage structure. These compounds were suggested as a molecular proxy for the occurrence and extent of thermochemical sulfate reduction (TSR). Compound-specific sulfur-isotope analysis of TDs may create a multi-parameter system, based on molecular and delta S-34 values that may be sensitive over a wider range of TSR and thermal maturation stages. In this study, we analyzed a suite of 12 Upper Jurassic oil and condensate samples generated from source rocks in the Smackover Formation to perform a systematic study of the sulfur isotope distribution in thiadiamondoids (one and two cages). For comparison we measured the delta S-34 composition of benzothiophenes (BTs) and dibenzothiophenes (DBTs). We also conducted pyrolysis experiments with petroleum and model compounds to have an insight into the formation mechanisms of TDs. The delta S-34 of the TDs varied significantly (ca 30 parts per thousand) between the different oils depending on the degree of TSR alteration. The results showed that within the same oil, the one-cage TDs were relatively uniform, with S-34 enriched values similar to those of the coexisting BTs. The two-cage TDs had more variable delta S-34 values that range from the delta S-34 values of BTs to those of the DBTs, but with general S-34 depletion relative to one cage TDs. Hydrous pyrolysis experiments (360 degrees C, 40 h) with either CaSO4 or elemental S (equivalent S molar concentrations) and adamantane as a model compound demonstrate the formation of one cage TDs in relatively low yields (