Study on diagenesis of organic matter in immature rocks

Since many immature oils have been found in a number of Tertiary basins of China, a series of cores (Oligocene) and several immature rocks after thermal simulation have been investigated for their biomarker distributions by GC and GC-MS. The presence of biomarkers in the cores seem to follow a rule of less to greater stability of hopenes, ββ-hopanes, diasterenes with increasing the depth of cores, and subsequently the 22R, 22S configuration of hopanes reaches equilibrium. The thermal simulation experiments with immature rocks demonstrated that it is possible to generate some immature oils from immature rocks during the diagenesis stage. The tricyclic terpanes generated from source rocks during diagenesis stage tended to be enriched in the oils compared to their source rocks and the relative abundance of lower molecular weight tricyclic terpanes to their higher molecular weight homologues may be useful for the subdivision of diagenesis.     

Extended saturated and monoaromatic tricyclic terpenoid carboxylic acids found in Tasmanian tasmanite

A series of tricyclic terpenoid carboxylic acids (C₂₀–C₄₀) was found in the acidic fraction of Tasmanian tasmanite bitumen, occurring as a mixture of stereoisomers with mainly the 13β(H), 14α(H)-and 13α(H),14α(H)-configurations. These dominant acidic tricyclic constituents have the same carbon skeleton as the ubiquitous tricyclic terpane biomarkers. A novel series of ring-C monoaromatic tricyclic terpenoid carboxylic acids was also characterized. The series ranges from C₁₉ to C₃₉ and is the acidic counterpart of the recently described series of monoaromatic tricyclic terpanes.     

混合原油的甾萜类和多环芳烃标志物短期风化规律研究

将胜利和塔西两种原油以不同比例混合后置于人工气候箱进行风化模拟实验,采用气相色谱质谱联用仪(GC-MS)检测风化样品中的生物标志化合物,探讨和揭示短期风化作用对混合溢油常用的甾萜类和多环芳烃诊断指标的影响。结果表明经过15d的短期风化,在混源比例大于10%时,各系列混合油样的甾萜类生物标志物诊断指标与单一油品的相关诊断比值的差异性和混源油品比例值呈明显正相关。各系列混合油样中的常用萘及烷基萘等指标不适宜作为短期溢油来源鉴别的指标,但可以作为溢油是否发生混合的间接判定指标。根据常用的多环芳烃相关诊断指标,可将各系列油样的短期风化模式依据混源油品中塔西油田原油所占比例大致分为3类(20%~50%、10%和0%)。多环芳烃系列诊断指标的相对标准偏差(RSD%)与混源油品比例有关,混源塔西油样的比例越高,PAHs系列指标的RSD%越大,稳定性越差。     

Identification of bicyclic terpenoid hydrocarbons in the saturate fraction of Athabasca oil sand bitumen

The bicyclic terpanes reported to be present in numerous petroleums have been detected in the saturate fraction of the Athabasca oil sand bitumen. This series of compounds has been found to extend from C₁₅ to at least C₂₄ and their structures have been established by means of comparisons with synthetic C₁₈ and C₂₀ samples of known stereochemistry.     

Organic geochemistry of geographically unrelated tasmanites

The biomarker analysis of three tasmanite rock samples from Tasmania, Alaska and Brazil showed an unusually high tricyclic terpane concentration relative to hopanes and steranes. A possible product-precursor relationship is advanced, associating Tasmanaceae alage with these tricyclic terpanes. These results support the search of possible precursor molecules in present day organisms which may be taxonomically related to these algae.     

泌阳凹陷湖相碳酸盐岩中的三环二萜烷及其热演化

从泌阳凹陷下第三系湖相碳酸盐岩中检测到了丰富的并以成对分布为特征的三环二萜烷。整个碳酸盐岩剖面中有机质类型均以Ⅰ型为主,成对分布的三环二萜烷中１３α（Ｈ）,１４α（Ｈ）异构体向热稳定性更高的１３β（Ｈ）,１４α（Ｈ）异构体转化,其含量随埋深的增加而减少。据此提出可以三环二萜烷热演化参数ＴＣＴ,即αα构型向βα构型转化率来表征未成熟和低成熟生油岩中有机质的热演化程度。     

Terpenoid biomarker distributions in low maturity crude oils

Twenty-seven heavy crude oils of diverse origin were geochemically assessed with respect to both bulk and mlecular composition for the purpose of identifying and quanttfying valid biomarker parameters for low maturity oils. The low thermal maturity level of many of these oils is evident from the bulk and alipathic chromatographic data, and oil sourced from both marine and terrigenous organic matter are represented. Selective metastable ion monitoring (SMIM) was employed to measure separately the distribution of C₂₇, C₂₈, and C₂₉ sterane isomers. The useful maturity indicators include the C₂₉ 5α(H) 20S/20R ratio, the relative quantity of the biological sterane configuration in each of the total normal C₂₇, C₂₈, and C₂₉ steranes, and the rearranged to normal sterane ratio. In addition, C₂₇ rearranged steran es appear to form at a faster rate than C₂₈ or C₂₉ rearranged steranes. However, the isomerization of the C₂₇ biological component appears to occur at a slower rate than the C₂₉ counterpart suggesting that the former may be used as a maturity parameter at higher levels of thermal maturation. In the triterpane distributions, the C₂₇ trisnorhopane isomers and the moretane to hopane ratios appear to be both source and maturity related and cannot be used as successful maturity parameters in oils unless they share a common source. The C₃₁₊ hopane 22S/22R equilibrium ratio appears to increase with increasing molecular weight (C₃₁–C₃₄).