The United Kingdom is well placed within Europe in having large reserves of indigenous coal both onshore and offshore in the southern North Sea. These reserves have the potential to provide security of future energy supplies long after oil and natural gas are exhausted.
Traditional mining methods however are not suited to working offshore reserves, and development and infrastructure costs of new mines can render the exploitation of landward reserves uneconomical. The concept of gasifying coal underground and bringing the energy to the surface as a gas for subsequent use in heating or power generation has considerable attraction. Underground coal gasification (UCG) has the potential to provide a clean and convenient source of energy from coal seams where traditional mining methods are either impossible or uneconomical.
As a coal-mining operation requiring a licence under the Coal Industry Act 1994, The Coal Authority has a vital interest in UCG.
UCG is the partial in-situ combustion of a deep underground coal seam to produce a gas for use as an energy source. It is achieved by drilling two boreholes from the surface, one to supply oxygen and water/steam, the other to bring the product gas to the surface. This combustible gas can be used for industrial heating, power generation or the manufacture of hydrogen, synthetic natural gas or other chemicals. The gas can be processed to remove carbon dioxide (CO2) before it is passed on to end users, thereby providing a source of clean energy with minimal green house gas emissions.
Government policy is to encourage the development of cleaner coal technologies for application both at home and in overseas markets. The potential for UCG in the UK relates not only to reducing environmental emissions but also to ensuring security of energy supply and maintaining an acceptable level of diversity of energy supply.
The basic feasibility of UCG has been proven in previous trials. Further detailed studies are required to prove the technology of precision drilling process control over sustained periods of operation and to fully evaluate any possible environmental impact on underground aquifers and adjacent strata. One of the practical problems of UCG is that meaningful experiments cannot be carried out in the laboratory, and trials must be undertaken at pilot scale, which is both costly and time consuming.
An EU trial, sponsored in part by the UK's Department of Trade and Industry (DTI), has demonstrated the feasibility of UCG at depths typical of European coal. The DTI concluded that the UCG process has potential for UK coal reserves, particularly when considering the large quantities of offshore coal potentially available.
Technology targets for UCG were set in DTI Energy Paper 67 and a programme of studies has taken place with industry to critically assess the commercial feasibility of UCG.
The technology, if successful, has export potential to countries such as China and India where coal reserves considerably exceed oil and gas reserves.
Development of UCG to date
UCG is conceptually very simple but the development of a working system has proved more difficult in practice. The main problems are drilling the boreholes, controlling the reaction within the seam and producing a gas of a consistent and high quality.
The gasification of coal seams in situ was first developed in the former Soviet Union during the 1930's and commercial-scale schemes have been developed since the Second World War with one at least project in Uzbekistan is still operating today.
In the 1950's, Britain embarked on its own long-term trial in shallow coal seams at Newman Spinney, Derbyshire, and although gasification was successful, the National Coal Board later abandoned the project for economic reasons.
US trials in the 1970s proved the value of new technology from the oil and gas industry to control the process. These were followed up in Europe by studies which concluded that the process was technically feasible in the thinner and deeper coal seams of Western Europe.
This led to the European trial of UCG in deep seams, which took place in Spain between 1992 and 1999. The DTI was a part sponsor, alongside the EU and Spanish and Belgium organisations.
The European trial was the first to use in-seam directional drilling at depth to construct the production well and the trial demonstrated that UCG wells in deep seams could be successfully constructed. The encouraging results of the European trial led the DTI to reevaluate UCG as a longer-term option for clean coal exploitation in the UK, as described below.
UCG and the DTI Clean Coal Research & Development Programme
The DTI review of cleaner coal technology, published as Energy Paper 67 in June 1999 examined the potential of UCG and other technologies like coal bed methane in the UK.
While these technologies were far from being considered commercial alternatives to conventional mining, and substantial R & D effort was required, it was accepted that further work on cleaner coal power generation technologies was a priority task.
During the consultation exercise a number of consultees suggested that UCG could offer an alternative way to obtain the energy from coal without mining and would also provide access to the large-scale UK coal resources inaccessible by conventional mining - including the substantial resources under the southern North Sea.
For this reason, and with regard to the total project cost of the order of £15-20 million, it was judged that the UK alone could undertake the next stage of a sub-commercial programme. This would be more expeditious than seeking European partners. If however the tests were successful, partners would be sought for a full-scale semi-commercial UCG trial.
Energy Paper 67 identified a series of technology targets for UCG that would need to be addressed over the next six years. These were:
- Improving the accuracy of in-seam drilling
- Examining the implications of burning UCG gas in gas turbines
- Estimating the landward coal reserves for UCG
- Identifying a semi-commercial site
- Establishing cost parameters for the process to be competitive
- Carrying out a pre-feasibility study of offshore exploitation of UCG
- The aim was to achieve these goals, in association with industry, over the next six years.
As part of the programme the Coal Authority became involved in research into UCG and it was the Authority who initiated Phase 1 of the programme which was to identify possible UK trial sites, outline a demonstration programme and review the environmental, utilisation and drilling technologies. However, the Authority was unable to progress beyond Phase 1 because of restrictions of its powers under the 1994 Coal Industry Act and the work was transferred to the DTI.
The development programme still continued through these arrangements, but limited to a series of desk studies.
By mid 2003, the various studies were nearing completion, and the DTI prepared a report, to sum up and publicise the status of the work. This report "Review of the feasibility of Underground Coal Gasification in the UK" was published in October 2004 (DTI/Pub URN 04/1643).
In 2007 certain functions from the DTI, including responsibilities for energy, were merged with the Better Regulation Executive (part of the Cabinet Office) to form the Department for Business, Enterprise and Regulatory Reform; further re-organisation led to the formation of the Department of Energy and Climate Change (www.decc.gov.uk) who now have responsibility for energy matters.
There are now signs that current issues relating to green house emissions and global price increases in gas are generating higher levels of interest in UCG and in 2009 and 2010 the Authority received applications for, and granted, some 14 conditional near offshore UCG licences to companies, keen to pursue the technology further in Great Britain. These conditional licences enable prospective operators to secure the rights to the coal while projects are developed but do not permit UCG operations to commence until all other rights and permissions are in place.
The UCG Partnership, now known as the UCG Association, was formed in late 2005 as a non-profit organisation set up to promote UCG technology around the world. The Coal Authority is an associate non-shareholder member of UCG Association and as the licensing body for UCG in Great Britain is only there on a watching and advisory brief with no commercial interest.
Further details on the UCG Association can be found at www.ucgassociation.org