Details of Award
NERC Reference : NE/J016950/1
ENERGY: Mechanisms, distribution, and subsurface implications of clastic dyke and sill emplacement
Training Grant Award
- Lead Supervisor:
- Professor DM Hodgson, University of Leeds, School of Earth and Environment
- Grant held at:
- University of Leeds, School of Earth and Environment
- Science Area:
- Earth
- Marine
- Overall Classification:
- Earth
- ENRIs:
- None
- Science Topics:
- None
- Abstract:
- The post-depositional remobilisation and intrusion of coarse sediment from a sealed and overpressured parent sandbody into a finer grained host rock with a tensile strength, is widely documented in ancient sedimentary successions. Clastic intrusions indicate the rapid flow of sands (>0.3 cm s-1) into lower pressure settings to form clastic dykes and sills (injectites), and are not passive infill features (Neptunian dykes). Case studies documenting the occurrence, morphology, and dimensions of clastic injection structures have increased over the last decade. This is largely because of the direct impact that clastic intrusions can have on subsurface hydrocarbon reservoir production. Clastic injections can help or hinder hydrocarbon reservoir production performance by changing reservoir geometry, properties, and connectivity, particularly in deepwater successions. Clastic injections are sometimes identified in seismic sections, and sub-seismic examples are commonly identified in 1D core datasets (e.g. North Sea Mesozoic field). However, the need for improved understanding of the spatio-temporal distribution and the three-dimensional geometry of intrusions, and the pre-requisite conditions for injection of sands will help reduce uncertainties during reservoir appraisal and development, and in the evaluation of potential carbon capture and storage projects. To improve the subsurface prediction and kinematic understanding of clastic injection processes and products, a comprehensive outcrop dataset from well constrained stratigraphic succession, the Fort Brown Fm., Karoo Basin, South Africa, which will be integrated with petrographic analysis, and physical modelling experiments of intrusions under high hydrostatic pressures. Clastic dykes and sills are widely exposed in late Permian deepwater claystones in the SW Karoo Basin, South Africa. The injectites are sourced from 20-150 m-thick sand-rich submarine channel-levee and lobe systems (parent sandbodies), which are separated by 10-50 m-thick claystones, which are well exposed in the arid environment, and host a variety of injectite structures. The stratigraphy, palaeoenvironmental setting, and sandbody architecture of 1 km-thick submarine slope successions exposed in the Tanqua and Laingsburg areas is well understood after a decade of fieldwork by UoL researchers. However, the clastic injections have not been a research priority. Qualitative field observations suggest that the spatial distribution of injectites is closely related to sharp-based (erosion surfaces) or sharp-topped (abrupt abandonment) sand-prone intervals, and can occur as isolated features, or in complicated swarms of connected dykes and sills. The parent sandbodies have a narrow grain-size range (not coarser than fine-grained sand), but the intrusions weather in a distinctive manner suggesting an untested difference in grain-size, cementation and/or mineralogy. Clastic dykes and sills were injected upwards and downwards. The outcrop work will also help to inform the design of physical experiments developed in the Rock Deformation Laboratory, University of Liverpool. The experiments will aim to model the formation of injectites under confining pressures that can be raised to the equivalent of several kilometres burial to elucidate likely pre-requisite conditions prior to injection. Initial experiments planned will use alternating layers of wet sands and clays, which will be confined in all directions, and then a preferential shear will be added to act as a trigger mechanism. The geometry of the experimental injections will be constrained using serial slices or CT scans.
- NERC Reference:
- NE/J016950/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Open CASE
This training grant award has a total value of £70,603
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - RTSG | Total - Student Stipend |
|---|---|---|
| £13,812 | £8,508 | £48,284 |
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