R E Holdsworth
Natural fracture propping and earthquake-induced oil migration in fractured basement reservoirs
Holdsworth, R E; McCaffrey, K J W; Dempsey, E; Roberts, N M W; Hardman, K; Morton, A; Feely, M; Hunt, J; Conway, A; Robertson, A
Authors
K J W McCaffrey
Dr Eddie Dempsey E.Dempsey@hull.ac.uk
Senior Lecturer in Structural Geology and Geohazards
N M W Roberts
K Hardman
A Morton
M Feely
J Hunt
A Conway
A Robertson
Abstract
The geological processes that create fluid storage capacity and connectivity in global fractured basement reservoirs are poorly understood compared to conventional hydrocarbon plays. Hosting potentially multi-billion barrels of oil, the upfaulted Precambrian basement of the Rona Ridge, offshore west of Shetland, gives key insights into how such reservoirs form. Oil presence is everywhere associated with sub-mm to m-thickness mineralized fracture systems cutting both basement and local pre-seal cover sequences. Mineral textures and fluid inclusion geothermometry suggest a low temperature (90-220ºC), near-surface hydrothermal system, as does the preservation of clastic sediments in the same fractures. These fills act as permanent props holding fractures open, forming long-term fissures in the basement that permit oil ingress and storage. Calcite fill U-Pb dating constrains the onset of mineralization and contemporaneous oil charge to the Late Cretaceous. The additional preservation of oil-stained injected sediment slurries and silica gels along basement faults suggests that rift-related seismogenic faulting initiated lateral oil migration from Jurassic source rocks into the adjacent upfaulted ridge. Subsidence below sea level in the latest Cretaceous sealed the ridge with shales, with buoyancy-driven migration of oil into the pre-existing propped fracture systems continuing long after the cessation
Citation
Holdsworth, R. E., McCaffrey, K. J. W., Dempsey, E., Roberts, N. M. W., Hardman, K., Morton, A., …Robertson, A. (2019). Natural fracture propping and earthquake-induced oil migration in fractured basement reservoirs. Geology, 47(8), 700-704. https://doi.org/10.1130/G46280.1
Journal Article Type | Article |
---|---|
Acceptance Date | May 3, 2019 |
Online Publication Date | May 22, 2019 |
Publication Date | May 22, 2019 |
Deposit Date | May 8, 2019 |
Publicly Available Date | May 31, 2019 |
Journal | Geology |
Print ISSN | 0091-7613 |
Electronic ISSN | 1943-2682 |
Publisher | Geological Society of America |
Peer Reviewed | Peer Reviewed |
Volume | 47 |
Issue | 8 |
Pages | 700-704 |
DOI | https://doi.org/10.1130/G46280.1 |
Public URL | https://hull-repository.worktribe.com/output/1759100 |
Publisher URL | https://pubs.geoscienceworld.org/gsa/geology/article/47/8/700/570815/Natural-fracture-propping-and-earthquakeinduced |
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