四川南桐煤矿区长兴灰岩中油苗的地化特征

长兴灰岩中的原油主要表现为陆源有机质的特征。富含高分子量正烷烃,富含长链无环类异戊二烯烷烃、倍半萜烷和C₂。甾烷,五环三萜烷组分中以一种未知结构的C₃₀(X)化合物为主,还检出四种C₂₄四环萜烷。油苗可能主要来源于龙潭组煤层。

GEOCHEMICAL CHARACTERISTICS OF THE SEEP OIL FROM THE PERMIAN CHONGXING LIMESTONE IN NANTONG COAL MINE AREA,SICHUAN PROVINCE,CHINA

A mature seep oil was discovered in the limestone of Permian Chongxing group which is just underlain by the coal beds of Permian I.ongtan group. It is proposed through oil-source rock correlation of biomarkers and stable carbon isotope ratios that the seep oil was mainly sourced from such source rock as the No. 4 Longtan coal bed, in which the suberinite is abundant in coal macerals. The crude oil is rich in n-al-kanes of high molecular weight, long chain acyclic isoprenoid alkanes, and sesquite-rpanes and possesses the predominant C₂₉ component in steranes. An unknown structure compound C₃₀(X) is the major peak in pentacyclic triterpanes. Four C₂₄ tetracyclic terpanes were detected in the crude oil, one is 17,21-secohopane, three other tetracyclic terpanes are structure-unknown compounds with the characteristic mass fragments, e. g. m/z: 191 (base peak), 109, 123,330(M⁺), 315(M-15), etc.. The crude oil has low hopane/sterane ratio below unit, and is rich in tricyclic terpanes with C₁₉-C₂₉, which means that microbial contribution can not be negligible in its sources besides major terrigenous organic matter.