Key Facts on UCG »

Introduction to Underground Coal Gasification Technology

Coal - the future

Underground Coal Gasification (UCG) is the gasification of coal in-situ, which is achieved by drilling boreholes into the coal and injecting water/air or water/oxygen mixtures. It is both an extraction process (like coal mining) and a conversion process (gasification) in one step,producing a high quality, affordable synthetic gas that can be processed to provide fuels for power generation, diesel fuels, jet fuels, hydrogen, fertilisers and chemical feedstocks.

The technique offers many financial and social benefits over traditional extraction methods, most notably lower emissions, as no coal is brought to the surface and the gas can be processed to remove its CO2 content. It can be used for heating, power generation, hydrogen production, or the manufacturer of key liquid fuels such as diesel fuel or methanol.

Interest in UCG as a secure and economic source of energy has increased over the past five years, most coal producing countries now have a comprehensive UCG programme comprising of feasibility studies, planning demonstrations and commercial scale projects.In-seam and Directional Drilling technology, formulated for the oil and gas industry, has transformed the UCG process, making it easier, more succesful and more commercially viable.

Commercial scale projects have started in Australia, China, South Africa, India. Large-scale operations (>1GW) were developed by the Soviets in the 1970's and at least one plant in Uzbekistan still operates today.Low natural gas prices in the 1990's eliminated much of the ongoing development in US, although in Europe, a substantial programme of development in deeper seams was maintained until the present day. Extensive trials in Europe, the US, Russia, Australia, have proven the technology on many occasions. UCG in combination with CCS (CO2 capture and storage) shows considerable promise as a low cost solution to carbon abatement. The composition of the syngas is particularly suited to CO2 capture and the high pressure from deep UCG will require smaller and less costly plant. The possibility of storing CO2 in nearby coal seams is a further option.

The Basic UCG Process - The basic UCG process has two wells drilled into the coal, one for injection of the oxidants, another to bring the product gas to surface. Coal has considerable variation in its resistance to flow, depending on its age, composition and geological history, so simply relying on the natural permeability of the coal to transport the gas is generally not satisfactory. High pressure break-up of the coal with water (hydrofraccing), electric-linkage and reverse combustion have all been used with success in both pilot and commercial scale operations.

. UCG plant

Different Methods - Two different methods of UCG have evolved, both are commercially availableThe first, based on technology from the former Soviet Union, uses vertical wells and a 'reverse' combustion to open up the internal pathways in the coal. The process has been tested (1999-2003) in Chinchilla, Australia using air and water as the injected gases.The second, tested in European and American coal seams, creates dedicated in-seam boreholes, using drilling and completion technology adapted from oil and gas production. It has a moveable injection point known as CRIP (controlled retraction injection point) and generally uses oxygen or enriched air for gasification.

In-seam and Directional Drilling

In-seam drilling was identified at an early stage as an option, but steerable drilling in coal only started to become available in the latter stages of the US programme of UCG (1975-1990). The breakthrough came when directional in-seam drilling was combined with CRIP. This arrangement provided an unobstructed path for the departing gases.

Site Selection

Site selection is paramount to a successful UCG project. The characteristics of the coal seam, the permeability and fault structure of the local strata and the geology and hydrogeology of the area which surrounds the target coal seam must be fully understood. This requires the drilling of pilot bore holes to coal seam depth for coring and seam characterisation, and a good quality seismic survey (preferably 3D) of the whole area. The same method is used to when assesing the suitablility of an area for Carbon Capture and Storage and may offer synergies for UCG and CCS. Modelling of the hydrogeology will be required to meet ground water requirements. This detailed exploration work is one of the major upfront costs of UCG, as it is for conventional mining.

Benefits of UCG

UCG offers significant benefits, both fiancial and enviromental, over traditional coal mining or coal gasification methods. Plus a number of social benefits are evident,. local communities do not face the detrimental impacts that traditional mining brings and local communities may benefit from the creation of associated infrastructure: roads, subsidised energy, and employee spending in the local economy.

Financial Benefits

Capital and operating costs are lower than in traditional mining
Reduced cost of plant installation - No Surface Gasifier
Syngas can be piped directly to the end-user, reducing the need for rail / road infrastructure
Lowers the cost of environmental clean up due to solid waste being confined underground
CCGT power plants can be switched from natural gas to cheaper UCG product gas
Manufacture of chemicals such as ammonia and fertilizers
Synthesis of liquid fuels at a predicted cost equivalent to US$20/barrel
Enhanced Oil Recovery (EOR) by injection of stripped CO2

Environmental Benefits

UCG may not require an external water source to operate, a major environmental advantage over water-intensive coal mining operations and pulverised-coal-fired energy production methods
Lower emissions, because gasification in UCG is underground thereby reducing environmental management costs
Particulates are generated at half the rate of their surface equivalents and stay underground
Lower fugitive dust, noise, visual impact on the surface
Low risk of surface water pollution
Reduced methane emissions - coal seam gas is recovered in the process, rather than lost in the atmosphere as in most conventional mining
No dirt handling and disposal at mine sites
No coal washing and fines disposal at mine sites
Smaller surface footprints at power stations
Lower water recovery and significant surface hazard liabilities on abandonment

THE OPPORTUNITY - The level of global activity in and interest in Clean Coal research and development offers up many opportunities.

Employment and Skills Training - Those with technical knowledge of gasification processes, general experience in power generation, oil and gas services and process plant construction, drilling, geophysical and geological skills, can grow their client base, develop their expertise and further their careers as UCG is a multidisciplined technology.t also offers new career paths for young engineers, geologists and other technical specialists. The UCG Partnership is extremely active in developing pertinent training courses to develop and hone the skills required by this growing industry and by linking with universities and academia around the world to ensure knoweledge of UCG is being passed to the next generation of operatives.

Commercialisation - The commercial potential in all these activities also needs to be embraced by governments, energy groups, financial institutions and investors.The commercial market is now beginning to embracing this knowledge to support new projects. The UCG Partnership will play an important part as an information source for those in the commercial arena such as Banks, Analysts, Lawyers, Brokers, Accountants, Project Managers, Risk Assessors, Private Equity Providers and Fund Managers