摘要：Solid bitumen in reservoir rocks is an allochthonous organic matter formed from bitumen or liquid hydrocarbons by various alteration processes. In this study, two types of altered solid bitumen have been identified in both the Ediacaran Dengying and Cambrian Longwangmiao formations in the Central Sichuan Basin using petrographic, microthermometric, chemical, and isotopic data. The hydrothermally altered bitumen (type 1) is associated with the pore-filling saddle dolomite and quartz in which homogenization temperatures of some fluid inclusions are more than 10 degrees C higher than the maximum burial temperature of the Dengying Formation. It has various anisotropic textures with significantly high bireflectance values (R-bmax - R-bmin%) between 3.89% and 9.21%. Moreover, the hydrothermal alteration led to C-13-enrichment in the type 1 bitumen compared to the normally matured bitumen derived from the same source. On the other hand, the thermochemical sulfate reduction (TSR)altered bitumen (type 2) has S/C atomic ratios of up to approximately 0.06. The delta(34)s values of type 2 bitumen are close to those of the carbonate-associated sulfate and similar to the TSR-derived H2S in the same reservoirs. A strong negative correlation exists between S/C atomic ratios and delta C-13 values in the type 2 bitumen in the Dengying Formation, which is interpreted as a result of an increasing incorporation of the C-13-depleted ethanethiol into the bitumen during TSR. This interpretation is consistent with the fact that the remaining ethane became isotopically heavier as TSR proceeded. In addition, the reactive sulfate for TSR was primarily derived from the hydrothermal sulfate, such as barite. This is evidenced by the replacement of hydrothermal barite by the S-34-enriched pyrite and the small differences in delta S-34 value between the barite and the type 2 bitumen (or the TSR-derived H2S) in the same strata. We suggest that TSR in the Ediacaran and Cambrian hydrocarbon reservoirs was probably initiated by hydrothermal activity.

关键字：Ediacaran and Cambrian Solid bitumen Carbon and sulfur isotopes Hydrothermal activity TSR Sulfur source

ISSN号：0301-9268

卷、期、页：卷: 321 页: 277-302

发表日期：2019-02-01

期刊分区（SCI为中科院分区）：一区

收录情况：SCI（科学引文索引印刷版）,ESI（基本科学指标数据库）,SCIE（科学引文索引网络版）

发表期刊名称：PRECAMBRIAN RESEARCH

参与作者：蔡春芳,Gao, Ping,Xu, Chenlu

通讯作者：张鹏伟,万伟超,张毅颖,江梦雅

第一作者：柳广弟,李美俊,陈睿倩

论文类型：期刊论文

论文概要：张鹏伟,柳广弟,蔡春芳,李美俊,陈睿倩,Gao, Ping,Xu, Chenlu,万伟超,张毅颖,江梦雅，Alteration of solid bitumen by hydrothermal heating and thermochemical sulfate reduction in the Ediacaran and Cambrian dolomite reservoirs in the Central Sichuan Basin, SW China，PRECAMBRIAN RESEARCH，2019，卷: 321 页: 277-302

论文题目：Alteration of solid bitumen by hydrothermal heating and thermochemical sulfate reduction in the Ediacaran and Cambrian dolomite reservoirs in the Central Sichuan Basin, SW China