Alkylbiphenyls in ancient sediments and petroleums

C₁ and C₂-alkylbiphenyls have been analysed in crude oils and sediment extracts by capillary gas chromatography after preliminary isolation procedures involving TLC and HPLC. The abundance of 2-methylbiphenyl relative to 3-methylbiphenyl has been measured in samples from two sedimentary sequences. 2-Methylbiphenyl decreases in relative abundance with increasing thermal maturity of the sediments in both sedimentary sequences. These isomeric methylbiphenyls are potentially useful as thermal maturity indicators for crude oils.     

地球化学模式及成因初探

如何对已发现的地球化学异常进行解释与评价，一直是困扰勘查地球化学家的难题。针对这一难题，笔者提出了地球化学模式的3种分类方案：规模分类、成因分类和成熟度分类。按照规模大小将地球化学模式分为：局部异常、区域异常、地球化学省、地球化学巨省和地球化学域， 同时将规模达地球化学省以上，并且内部具有套合结构特点的立体地球化学模式称作地球化学块体。地球化学模式依成因可分为原生地球化学模式和次生地球化学模式。成熟度分类是笔者首次提出，地球化学模式的成熟度是指地球化学异常相对于矿的关系而言的。笔者将地球化学模式按成熟度的不同，依次分为原始地球化学模式，中间地球化学模式和终极地球化学模式。提出成熟度分类是试图为科学利用所发现的地球化学模式进行异常解释与评价提供理论依据。     

克拉通盆地内油气垂向微渗漏的烃类地球化学──以鄂尔多斯盆地城川1井为例

通过对鄂尔多斯盆地腹部城川１井（０─４５００ｍ）酸解烃、热解烃及部分层段抽提烃的系统研究，结合剖面上有机质含量的变化及产油气层的分布，讨论了油气垂向微渗漏在浅层沉积层中留下的可识别的地球化学痕迹。该井浅层０─１０２０ｍ井段，有机碳含量低，在０．０６％─０．３％之间，平均为０．１１％，ｔ（ｍａｘ）值小于４００℃，有机质处于未成熟热演化阶段，岩性发育以红色、砖红色粉砂岩和浅灰色砂质泥岩和粉砂岩为主，这样一套沉积组合显然不利于有机质转化成烃。但与其下伏相邻成熟层段相比，Ｓ１／ＴＯＣ，Ｓ１／（Ｓ１十Ｓ２）和Ｃ（２＋）／ＴＯＣ均异常偏大，饱和烃的ＯＥＰ值为１．１１─１．１３，饱／芳值为５．２─６．４，显示了不具有奇偶优势的成熟烃的特征；经丙烯均一化之后，浅层甲烷和重烃异常并未消失，表明有深部热成因气态烃的加入。盆地内断裂不发育，则通过岩石中微裂隙和孔隙系统的油气微渗漏是深部油气运移的主要方式。由此可见，油气垂向微渗漏在浅层沉积层中留下了可识别的地球化学痕迹。     

不同成因原油全扫描定量荧光特征及其影响因素

为揭示不同成因类型原油的三维全扫描荧光特征及其主控因素,对50个不同成因类型的原油的三维荧光特征进行了分析。原油样品代表了未熟—低熟至高成熟度范畴原油、淡水与咸水湖相、沼泽相成因原油、高蜡低硫与低蜡高硫油、常规油与重质油等类型。结果表明,分析原油三维荧光谱图及其定量参数有所差异。原油的荧光强度随芳烃含量增加而增加,沼泽相高蜡油荧光强度总体高于湖相原油;荧光强度随成熟度增加而降低、荧光主峰波长随成熟度增加而变短,反映芳烃总量与相对高分子量芳烃丰度具有降低趋势。稠油的荧光谱图不同于常规油,具有波长分布范围宽、主峰不明显等特征。成熟度、母源岩有机质类型与生源、次生改造等多种因素对原油的三维荧光特征有控制作用。     

噻吩类化合物——判识海相原油类型和评价高演化碳酸盐岩烃源岩成熟度的理想生物标志物

现被广泛应用的有机岩石学成熟度评价方法和有机地球化学成熟度参数在评价海相高演化碳酸盐岩烃源岩时具有很大的局限性。噻吩类化合物具有高度的热稳定性和抗微生物分解性,在碳酸盐岩中含量丰富,易于鉴定和定量计算,成熟度参数值跨度大,用其判识塔里木盆地原油的烃源岩类型、区分塔里木盆地高成熟原油的成熟度取得了良好的效果。通过进一步研究其成熟度参数与 R_0的关系,可望建立海相高演化碳酸盐岩成熟度评价标准和方法。     

Unusual N—Alkane Distributions in Extracts from Marine Carbonate Rocks at High Levels of Maturity and Overmaturity

N-alkanes in extracts from possible carbonate source rocks of the Lower Ordovician Majiagou Formation in the central gas field of the Shanganning Basin and the Upper Sinian Dengying Formation in the Weiyuan gas field of the Sichuan Basin, are characterized by bimodal distributions with the dominant carbon numbers in the range C₁₇-C₂₁ and C₂₅-C₂₉. In most samples, the lower carbon number components are present in greater abundance than the higher carbon number ones. Most samples contain significant concentrations of waxy hydrocarbons (C₂₂₊) with C_21-/C₂₂₊ ratios between 0.50 to 3. 16, and an average value of 1. 34. The n-alkanes in extracts of outcrops and shallow core samples of Upper Proterozoic and Lower Palaeozoic carbonate rocks in the western and southern parts of the North China Basin are of unimodal distributions dominated by n-alkanes maximizing in the C₂₅-C₂₉ range. These extracts have very high concentrations of waxy hydrocarbons with C_21-/C₂₂₊ ratios all < 1. 0, ranging from 0. 14 to 0. 90 and averaging 0. 36. All of the extracts have a marked odd/even predominance in the high molecular weight n-alkane range regardless of whether they are from shallow or deep cores or out-crop samples. Simulation experiments were performed using typical sapropelic-type kerogens from the immature Sinian Lower Xiamalin Formation carbonate-rich shales collected at Jixian, Hebei Province, North China Basin, and the contemporary microplanktonic blue-green algaeSpirulina subsala. Results indicate that the unusual distribution of n-alkanes in the extracts of Upper Proterozoic and Lower Palaeozoic carbonate rocks possibly originated from algae in the source rocks at high levels of maturity and overmaturity. This research project was financially supported by the Chinese Academy of Sciences (Grant No. KZCX2-111 ).