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Genesis and role of bitumen in fracture development during early catagenesis

Abstract:
Bitumen-bearing fractures and vugs were investigated in the highly organic-rich Jordan Oil Shale (JOS) of Late Cretaceous to Eocene age, which has potential as a highly fractured, unconventional hydrocarbon play. Bitumen is present as macroscopically visible deposits and as inclusions in the cement of abundant natural fractures and adjacent vugs. The frequency of bitumen occurrence in fractures closely correlates with Total Organic Carbon (TOC) and burial depth. Petrographic and organic-geochemical analyses on bitumen samples extracted from fractures and their host rock matrix show that the fracture-filling bitumen comprises indigenous low maturity hydrocarbons derived from the surrounding organic-rich Oil Shale and has not migrated from a deeper source. Maturity indicators imply that the oil shale is in the pre-oil generation stage of early catagenesis throughout the investigated area, but with a regional increase in thermal maturity from west to east as the result of greater maximum burial depth. Bitumen mobilization in the host rock was mainly controlled by vertical loading stress acting on the non-Newtonian bitumen phase in load bearing configurations in the organic-rich matrix. Bitumen fractures were developed by hydraulic fracturing as the result of fluid overpressure in the organic matter. Overpressured bitumen has acted as a fracture driver, generating bitumen veins in both the organic-rich mudstones and the adjacent chert and silicified intervals.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1144/petgeo2018-179

Authors


More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Oxford college:
St Cross College
Role:
Author


Publisher:
Geological Society
Journal:
Petroleum Geoscience More from this journal
Volume:
25
Issue:
4
Pages:
371-388
Publication date:
2019-08-06
Acceptance date:
2019-07-31
DOI:
EISSN:
2041-496X
ISSN:
1354-0793


Language:
English
Keywords:
Pubs id:
pubs:1036969
UUID:
uuid:1f50d143-c243-481d-8f72-85935272eec7
Local pid:
pubs:1036969
Source identifiers:
1036969
Deposit date:
2019-08-01

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