Distribution and Origin of the Bitumen and Its Trace for the Hydrocarbon-expelling Pathway of Xujiahe Formation in Yuanba Area of Sichuan, China(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2018年第01期
- Page:
- 1-10
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Distribution and Origin of the Bitumen and Its Trace for the Hydrocarbon-expelling Pathway of Xujiahe Formation in Yuanba Area of Sichuan, China
- Author(s):
- ZOU Hua-yao; HAO Fang; LI Ping-ping; ZHU Yang-ming; ZHANG Li; ZHANG Jun-wu; ZHANG Sheng-lei
- 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China; 2. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences, Wuhan 430074, Hubei, China; 3. School of Earth Sciences, Zhejiang University, Hangzhou 310027, Zhejiang, China
- Keywords:
- bitumen; overpressure hydraulic fracture; hydrocarbon-expelling pathway; Xujiahe Formation; triaromatic steroid; fracture; Yuanba area; Sichuan Basin
- PACS:
- P618.130.2
- DOI:
- -
- Abstract:
- Xujiahe Formation in Yuanba area of Sichuan, China, is composed of coal-bearing strata. Based on core observation and measurement, as well as organic geochemical analysis and bitumen-occurrence description, it is demonstrated that widespread solid bitumen presents within the fractures among argillaceous source rock and sandstone-conglomerate reservoir layers. The precursor of bitumen (namely palaeo-viscous oil) is generated from preferentially algae-rich organic matter in argillaceous source rocks, proved by using relative abundance correlation of triaromatic steroids contained in solid bitumen and extracted from argillaceous source rock and coal rock. Being viscous, the palaeo-oil easily remains along expelling route, consequently tracing the oil-expelling pathway. Combined with the analysis of overpressure evolution for Xujiahe Formation, a conceptual model of oil-expelling pathway is created, namely, a representative oil-expelling pathway model driven preferentially by overpressure. Oil-expelling pathway consists of two tempo-spatially continuous processes, including initial sweating and agglomerating into micro-fractures, and subsequent discharging along the micro/macro-fractures. Little is known about the initial process; but authentically, the discharging or expelling fractures are composed of hydraulic fractures occurred along laminae and bedding as well as across both of them, mainly formed by strong overpressure and tectonic stress. Consequently, the hydraulic fracture and the tectonic micro/macro-fracture are the most important expulsion-conduits.
Last Update: 2018-03-08