塔里木轮南地区原油沥青质的分子结构及其初步应用:热解、甲基化-热解和RICO研究

Molecular structure of oil asphaltenes from Lunnan area of the Tarim Basin and its applications: A study by pyrolysis, methylation pyrolysis and RICO

利用瞬间热解、甲基化-热解和钌离子催化氧化(RICO)降解技术研究了塔里木盆地轮南地区原油沥青质的分子结构,并对其在石油地球化学研究中的指示意义进行了讨论。轮南地区原油沥青质分子中的取代官能团以烷基侧链为主,烷基桥次之,另外还有少量的烷基-环己烷、支链烷烃和苯系物,这些化合物可能大都以C—C键结合到缩合芳环体系上;沥青质分子中的芳环体系大多数可能是萘或菲类型的芳香结构,高度缩合的芳香结构可能较少。轮南地区不同构造带原油沥青质热解产物的一致性指示它们可能来自沉积环境相同的母源。沥青质的分子结构表明,其母源可能主要来自浮游藻类的类脂物。热解产物中较高含量的1,2,3,4-四甲基-苯和2,6-二甲基、2,6,10-三甲基烷烃类化合物的检出表明其母质可能形成于较强的还原环境。沥青质热解产物中姥鲛-1-烯的相对含量较低,RICO产物中一元脂肪酸远高于二元脂肪酸,指示该区原油具有较高的成熟度。部分脂肪酸类化合物通过酯键连接在沥青质分子中,可能反映了原油在储层中经历了生物降解等后生作用。

The molecular structure of oil asphaltenes from Lunnan area of the Tarim Basin is elucidated by flash pyrolysis, methylation pyrolysis and Ruthenium Ion Catalyzed Oxidation (RICO), and the structure of asphaltenes is used in the study of petroleum geochemistry. The substituted functions in oil asphaltenes from Lunnan area are dominated by n alkyl side chains. N alkyl bridges and minor alkyl cyclohexanes, branched alkanes and alkyl benzenes are also identified. These functions maybe are linked to the structure of asphaltenes by C—C bonds. The aromatic ring systems of oil asphaltenes are mainly composed of naphthalene and phenanthrene and seldom of highly condensed aromatic rings. The molecular structure of oil asphaltenes from Lunnan area indicates that these oils mainly came from lipids of planktonic algae. The pyrolysates of oil asphaltenes from different tectonic belts of Lunnan area are similar, which suggests these oils came from sources under the same sedimentary environment. The identification of relatively high abundance of 1,2,3,4 tetramethyl benzene, 2,6 dimethyl alkanes and 2,6,10 trimethyl alkanes in pyrolysates of oil asphaltenes indicates the source of these oils were formed under strongly reduced sedimentary environment. Low abundance of pr 1 ene suggests high maturity of oils from Lunnan area, which are also supported by the fact that the n alkanoic acids are much more than di n alkanoic acids in yields of asphatenes by RICO. Some alphatic acids are linked to the structure of asphaltenes by ester bonds, and this maybe indicates the oil has been partly altered in reservoir by catagenesis, such as bio degradation.