OR/14/055 About the vitrinite reflectance dataset
| Linley, K A. 2014. User Guide for vitrinite reflectance data. British Geological Survey Internal Report, OR/14/055. |
Background
The UK has abundant shale at depth, although the distribution is not well known. The BGS is investigating the location, depth and properties of the shale as well as the processes that lead to economic accumulations of gas.
BGS has produced a review dataset, based on existing published analyse. The data has been compiled as part of ongoing research of shale gas basins through the use of conventional oil and gas well data to identify potential targets; for example, vitrinite reflectance of organic material within potential shale gas and oil source rocks.
This dataset represents the data gathered for this purpose and provides information on the content and variation within prospective some shale units. Characteristics which are a function of the original depositional setting, subsequent geological history and mineralogy are used to infer the possible presence of shale gas. A number of factors are considered in determining the quality of a source rock including:
- Total Organic Carbon (TOC)
- Net to gross organic-rich shale thicknesses
- Kerogen type
- Thermal maturity*
- Porosity and transport properties]
- Fracture properties
* Vitrinite reflectance (VR) is a recognised as a method for the evaluation of thermal maturation
The British Geological Survey has an ongoing development programme to produce datasets that inform and support research. A suite of energy related datasets are currently under development and these are complimented by existing BGS assets.
The data has been generated to provide an overview of VR values from shale rich horizons obtained from analysis of boreholes drilled across Great Britain. It has been derived from publications of analyses of organic-rich shale samples from BGS (formerly IGS) boreholes. Related products:
- DiGMapGB — digital geological data bedrock and superficial at a range of scales
- Scans of onshore borehole logs for Great Britain
- Scans of geology and historic topography maps
- Aquifer, shale and clay maps (https://www.bgs.ac.uk/research/groundwater/shaleGas/aquifersAndShales/maps/home.html)
- 3D models and cross-sections
- Total Organic Content
Who might require this data?
- Hydrocarbon exploration companies
- Hydrocarbon service companies
- Central government
- Academics
The vitrinite reflectance (VR) data provides VR values from shale-rich horizons identified in boreholes drilled across Great Britain. The data along with other energy data may be of interest to exploration companies and academics.
What the dataset shows?
Vitrinite reflectance is an evaluation method for thermal maturity of a source rock. Vitrinite is a maceral (a component, organic in origin, of coal or oil shale) which is formed through the alteration of lignin and cellulose in plant cell walls. The reflectivity of vitrinite macerals increase in response to thermal alteration and is used to define maturity levels and by projection to predict maturity at depth. Rocks buried at depth are subject to higher temperatures and as this increases vitrinite is altered through a process known as aromatization which increase the reflective properties.
Vitrinite reflectance is measured using a reflectance microscope and results recorded in terms of Reflectivity (R) representing the percentage of light reflected in oil known as Ro.