Details of Award
NERC Reference : NE/L009110/1
Hydro-fracture in the laboratory: Linking fracture networks to permeability and seismicity using rock physics as a laboratory tool.
Training Grant Award
- Lead Supervisor:
- Dr PM Benson, University of Portsmouth, Sch of Earth & Environmental Sciences
- Grant held at:
- University of Portsmouth, Sch of Earth & Environmental Sciences
- Science Area:
- Atmospheric
- Earth
- Freshwater
- Marine
- Terrestrial
- Overall Classification:
- Earth
- ENRIs:
- Biodiversity
- Environmental Risks and Hazards
- Global Change
- Natural Resource Management
- Pollution and Waste
- Science Topics:
- None
- Abstract:
- Hydrofracturing, commonly known in the popular press as fracking, is a process that describes how pressurised fluid is used to fracture the surrounding rock mass, typically by drilling a borehole through which high pressure fluids are pumped. This process is exploited in the oil and gas industries for releasing hydrocarbons from otherwise inaccessible formations; such resources are often termed unconventional oil. The need to fracture the rock is a central requirement as this allows the many small pockets natural gas to be accessed that were previously trapped by the naturally low permeability of the most common rock type involved, shale. However, the process is not without controversy. With each fracturing event, seismic energy is released in the form of a small magnitude earthquake. Whilst the magnitude of these microseismic (MS) earthquakes are small in comparison to tectonic earthquakes, they do have the potential to disturb the stability of the local geological formation as well as causing distress to the local population. In addition, whilst the majority of the MS earthquakes are indeed of low magnitude, there have been some cases of larger events. The need to create the permeable fracture network, and by definition the associated MS earthquakes, cannot be avoided but can be better understood through the discipline of rock mechanics. This describes the macroscopic behaviour of how rocks deform and fracture under the typical pressures and temperatures encountered at relevant depths. However, there is a problem. To date, there is a severe paucity of rock mechanics data for shale rocks. Because of this key missing requirement, many industrial fracking processes in the field have proceeded empirically (trial-by-error) and, whilst this approach remains valid, many hydrocarbon companies are now seeking to apply more robust and targeted approach to the process. A particular goal is to better use the generated MS earthquakes to provide both a source of data for monitoring the fracture zone extent, and as a warning tool, for example by linking a given fracture size to a given MS earthquake magnitude. Such knowledge would usefully allow the fracking process to be adjusted to avoid dangerous situations. In this project, these goals will be tackled by combining the latest laboratory microseismic instrumentation with representative shale samples to generate a geophysical image for accurately mapping the 3D fracture network in time and space, and with respect to key rock parameters of strength, bedding direction and under representative conditions of pressure and temperature. Crack networks will be generated by pressurising a central miniature borehole so as to replicate the conditions of fracking, but in a well-controlled laboratory environment. The project has three main objectives: Firstly, to explore the basic fracture mechanics behaviour (rock strength) with increasing fluid pressure and to asses the competition between the natural permeability of the undeformed rock, and the fluid pressure needed to create and maintain cracks of a certain size once new cracks have been generated. This is clearly a key driver for fracking in the first place; the required pressure needed to generate the suitable crack network that provides a given permeability is crucial to optimum reservoir performance. Secondly, to test the importance of inherent and induced anisotropy (the variation in physical parameters with measurement direction) on the fracture pattern, so as to improve the accuracy of MS monitoring. Thirdly, to explore the ability of the recorded seismicity to accurately record the fracture network and to forecast/estimate the risk of a given event size based on the measured stress state. Although MS earthquakes cannot be avoided, this project aims to better understand the fundamental physics (and risks) behind fracking in order to better optimise this key future energy resource.
- NERC Reference:
- NE/L009110/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Industrial CASE
This training grant award has a total value of £83,515
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - Student Stipend | Total - RTSG |
|---|---|---|
| £16,226 | £56,292 | £11,000 |
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