Independent Review of Underground Coal Gasification - Report

An independent examination of the issues and evidence surrounding Underground Coal Gasification.

3. Technology and Operational History and Issues

3.0 This chapter benefitted not only from a review of the literature but also from inputs provided in interviews and conversations with senior staff in the Coal Authority, regulators, former miners, academics and critically, industry experts.

3.1 According to Younger and Gonzalez (2010),

"The world's first UCG experiments were carried out beneath Hett Hill in county Durham in 1912, by Sir William Ramsay". Progress was halted by the First World War, and the technology was later neglected except in the former Soviet Union, where up to twelve UCG-based power plants were in operation in the mid-20 th Century. Although UCG production declined when natural gas reservoirs were found in the region, a 100 MW UCG power plant remains in production at Angren in Uzbekistan. Various pilot UCG operations have since followed elsewhere in Asia, Europe, the United States and Australia."

3.2 In the Geology Section, the approach to licensing UCG taken by the Coal Authority is mentioned. The CA, as well as HSE, essentially requires the operator of both generation, extraction and processing of UCG gases to demonstrate their method of operation and the environmental and safety dimensions of such operations.

3.3 The technologies involved are a combination of coal and oil and gas technologies and, as UCG is a gasification process, which happens to take place "in situ" or underground, the methods relate to accessing, initiating ignition in, maintaining combustion in and extracting product gas from an underground combustion chamber shaped by the geology of the location. The technologies and operational methods involved begin with the German engineer, William Siemens in the 1860s and have been refined and augmented by work in Durham and across the world since. A good summary for the time was set out by Burton et al (2007) and useful overviews are also in Lavis, Courtney and Mostade (2013) and in Osborne (2013). Osborne covers a very wide and detailed scope and "in situ" gasification, as UCG is sometimes called, is promoted as "a likely long term option in the safe, economic recovery of the large resources of coal unlikely to be considered mineable."

3.4 Process and Technology

The processes involved in the UCG industry - drilling, gas production and Syngas refining are described in Burton et al (2007), Lavis et al (2013) and a large number of other sources covered in the bibliography.

3.5 The chemical process at the heart of Underground Coal Gasification is the engineered injection of a blend of gasification (normally O 2, air, H 2O/steam) agents into the coal resource, their ignition, coal combustion and collection of the product gas.

3.6 Adrianopoulos et al (2015) describe the process in more detail.

"Following ignition, the reagents support the gradual transformation of the coal seam into syngas which is collected, transported to the surface and, depending on its composition (mainly H 2, CO, CO 2 and CH 4), can be used either as chemical feedstock or as fuel for power generation. The employment of directional drilling techniques to engineer the injection and production boreholes represents a significant advance, which is adopted from the oil and gas industry". Early methods were based on the use of two shafts - one for injection purposes and the second for venting or extraction."

3.7 They go on, "The two UCG subsurface layouts discussed in this paper are the Linked Vertical Wells ( LVW) and the Continuous Retracting Injection Point ( CRIP) geometries. Both geometries belong to the shaft-less UCG methods although their operational details are distinctly different." Adrianopoulos et al (2015)

3.8 As to technology more specifically and the different models, Jones et al (2004), describe UCG, as elsewhere, as

"the process by which steam and air or oxygen is injected into a coal seam via a surface injector well. These injected gases react with the coal to produce a combustible gas that is collected at the surface via a producing well (Creedy et al. 2001). Methane is a product of pyrolysis and gasification and its formation is favoured under high pressures. As part of the gasification process a cavity develops as the coal burns. Wilks (1983) predicted that the cavity that develops around the injection well would be pear-shaped, assuming that the reaction processes were uniformly distributed around the reactor and that the roof collapses immediately into the cavity formed by gasification (Creedy et al 2001). If the roof does not collapse the cavity will grow in size and some of the fluid reactant will by-pass the coal and the reactor efficiency will decline. This results in an O 2 rich product gas or a rise in the product temperature (Creedy et al. 2001). Hence in the UK, the UCG process is aided at depths greater than 500m by the high in situ stresses that characterise the UK Coal Measures which should ensure caving and thus reduce the possibility of by-passing (Creedy et al 2001).

3.9 "There are three main forms of UCG. The first involves drilling a series of vertical boreholes, gasifying the coals and relying on a combination of high pressure air fracing (sic)(pulses of air to open the cleats in the coal) and the natural permeability of the coals to extract the gas. This type of UCG generally takes place at shallow depths. An example of this is the Chinchilla project in Australia (Walker et al. 2001; Blinderman & Jones 2002). The low permeability of most UK coal is thought to preclude this method, although there may be exceptions in some coal structures. The second type of UCG takes place in existing or abandoned coal mines ( e.g. Liuzhuang Mine, China). In this process mined galleries are sealed off, air is injected into these galleries, the surrounding coal is gasified and the gaseous products piped up a shaft or borehole to the surface. The European and later US trials have involved the gasification of coals in which the production and injection wells are connected by in-seam drilling techniques. UCG is a cost effective means of extracting energy from coal because it avoids the high costs associated with mining and constructing a surface gasifier (typically hundreds of million pounds) and leaves ash and dirt underground. The recent technological achievements in UCG have been addressed by Creedy et al. (2001) and reference should be made to this report for details."

3.10 From these earlier documents it is clear that there are variations on a few themes - early shaft and bore models, which have become more sophisticated and controlled; mine and gallery and chamber models also developed early and applicable to some geologies amore than others and then CRIP - controlled retraction injection point - models whereby more precise drilling methods can be used, especially in deeper coals and narrower seams to allow for ignition points and gas injection and collection to be achieved on a more mobile and controlled basis as the "panel", or coal gasification unit, within a seam is burned out.

3.11 UCG worldwide

In this section the locations where UCG has been trialled and operated worldwide are identified. The material which follows also indicates the technology and method used at these locations in a range of cases.

3.12 Shafirovich and Varma (2009), Burton et al (2007), Creedy et al (2001), Green (2009), Lavis et al (2013) and FoEI/Monk (2016) all set out sequences and partial listings of UCG sites and although there are several discrepancies around timing and some other details, these do appear to address the most relevant cases and this has assisted in compiling the list at Annex 3. This is still not complete however and more research as well as greater operator openness would be required to make it complete and exhaustive as well as supply comparable information on each physical operation and what it has achieved as well as its impacts. Nonetheless, Annex 3 provides an overview of UCG projects worldwide and their approximate dates, depths and some salient details.

3.13 Jones et al (2004) at 11.1.1, p 44 also set out a history of UCG,

"There have probably been over fifty or so different UCG trials and larger schemes operated during the past 50 years or so. Early UCG trials usually took place at shallow depths (<200m); for example the Newman Spinney trial in the UK in 1959 was drilled to the Fox Earth Coal at a depth of 75m (Gibb & Partners 1964). These trials were generally of short time periods (1-2 months). The exception to this were the large-scale, air-blown schemes in Russia and Uzbekistan and a test at Chinchilla in Queensland, Australia, which was initiated by Linc Energy in December 1999 and was mothballed in 2003. The Russian and Australian schemes used simple technology and produced a low calorific value gas. China has considerable experience of UCG, with 16 trials completed since 1990. Feasibility studies have also been carried out in Canada, India, Pakistan, Russia, Slovenia and Ukraine, and a small burn was conducted in New Zealand in the early 1990's.

3.14 "Underground coal gasification has been carried out in Kuzbass, Siberia, at the Yuzhno-Abinskaya gasification plant since 1955. This involves the gasification of bituminous coal, 1.3 - 3.9m thick, producing a low calorific value gas used for heating (Walker 1999). The reprocessing volume achieved 2 million tons that constituted about 4 billion m 3 of gas.

3.15 "The Angren Coalfield is the largest coal deposit in Uzbekistan, containing about 1.8 billion tons of mostly brown coal (lignite) that is used as fuel for Uzbekistan's power generation. The Angren mine also has underground coal gasification technology in place since 1955 to produce gas for the Angren power station. The lignite seam varies in thickness from 4-20m and lies at depths of between 130- 350m. The output in 1963 was believed to be about 860 x10 8 m 3, but present production is about half of the 1963 figure (Walker 1999).

3.16 "There was much research carried out in the 1970s, and a number of trials went ahead. The Thulin scheme, in Belgium ran from 1978 to 1986 and gasified a thin seam at a depth of 1000m. In the US, UCG research has focused on relatively shallow (100m deep) coal seams and tests were focused on the development of the process itself. However, the Rocky Mountain 1 ( RM1) UGC test at Hanna, Wyoming, involved extensive site characterization, instrumentation and monitoring in order to gain a detailed understanding of the environmental and hydrogeological variables (Boysen et al. 1990; Creedy et al. 2001). Commercial projects were evaluated ( e.g. at Rawlins, Wyoming), but the low cost of gas in the early 1990's prevented these projects from being viable.

3.17 "The El Tremedal European trial in Spain (1993-1998) confirmed the technical feasibility of UCG at depths between 500-700m and has shown that improved deviated drilling techniques in deep seams can provide interconnected channels suitable for use in underground coal gasification (Green 1999). In this trial a controlled retraction injection point ( CRIP) system was used to control the gasification procedure (Green 1999).

3.18 "The IGCC project in Chinchilla, Australia began development in 1999, and was the first project to propose the use of UCG syngas directly in gas turbines (Blinderman & Jones 2002). The project involved construction of an underground gasifier and demonstration of the technology (Walker et al. 2001; Blinderman & Jones 2002). Approximately 32,000 tonnes of coal have been gasified, producing a low calorific value gas of about 5MJ/m 3 at a pressure of 10barg (145psig) and temperature of 300°C (Blinderman & Jones 2002). Nine process wells have been producing gas from a 10m thick seam at a depth of about 140m (Blinderman & Jones 2002). Ground water monitoring has also been taking place in association with this trial and has revealed no contamination (Blinderman & Jones 2002). This is probably related to keeping the gasifier pressure less than the hydrostatic pressure of fluid in the coal seam and surrounding strata (Blinderman & Jones 2002).

3.19 " UCG has been under review in the UK more or less since the early Newman Spinney trials in the 1950's. British Coal undertook major studies in the 1970's and 1980's and trial sites were identified in Nottinghamshire area towards the end of the 1980's as possible locations for the European trial - in the end the trial was located in Spain, as discussed above. The current UK programme was activated in 1999."

3.20 The DTI (2006) study by the team at Heriot Watt still appears to be valid and it sets the scene for key aspects of the work of Belltree (2014). This is the most detailed geological consideration available other than the detailed mapping and modeling capability of BGS. DTI (2006) includes 3D visualisations of well design, geo-mechanical issues and risks as well as some environmental consequentials. It also analyses economic factors and provides a very useful starting point for developers and consideration of the issues that Belltree then developed in their work for CNRL. The main area of change is around the consideration of CCS. Whilst an interesting and potentially key part of the 2006 model, this is at least, at present, beyond detailed consideration.

3.21 No other similar levels of detailed analysis have been found that relate to potential or operational sites. It is likely that these analyses exist and that much could be learned from them but the information is evidently held by developers and perhaps some regulators and is not accessible.

3.22 Dr. Cliff Mallett, the Technical Director at Carbon Energy and former chair of the UCG Association (2013-15), which has since ceased, has similarly reviewed the range of projects and technologies involved in the history of UCG from the perspective of an experienced operator. He refers (Mallett, 2015) to the "almost a hundred historical sites worldwide". He also observes,

3.23 "A commercial UCG plant has been running for many years in Uzbekistan; however detailed information on the operation or output of that plant has not been made public."

3.24 He also acknowledges in part the range of impacts and difficulties of the industry, citing the main difficulties encountered as:

  • Insufficient knowledge of the site geology
  • Inability to drill boreholes with necessary precision
  • Operating with inappropriate gasification parameters
  • Lack of understanding of the impact of the gasification process on the surrounds of the underground cavity."

3.25 He goes on then to cite the major technical innovations which have addressed the issues previously encountered (simplified here):

  • Geology - advances in mining: 3D seismic surveys and computer-based geologic models
  • Drilling - advances in long-hole in-seam drilling methods
  • UCG Design and Gasification Process Control - development of proprietary new modelling and design capability and process methods for real-time control of operations as well as development of parallel controlled retracting injection point design (an enhancement of the previously leading CRIP method)
  • Ground and water impacts around the gasifier - mine strata and gas models for prediction of deformation and gas and water inflow into mines

3.26 The (2015) article concludes,

"Since 2000, long-term UCG pilots in Australia, China, and South Africa utilizing the technologies shown in Table 2 have successfully demonstrated that deep UCG can be low cost and environmentally benign. Results from these trials continue to demonstrate that UCG's major challenges have been resolved and has led China to incorporate this technology into its Five- Year Plan process for resources and energy.

3.27 Recent progress and innovation have made it possible that UCG will be an important technology in the future energy mix. However, progress in nontechnical areas must be made with respect to the interrelated areas of government regulation, community understanding and engagement, and project financing."

3.28 These latter points seem especially telling, not least in the context of the subsequent Queensland ban. Also, it is again worth looking at Moran et al (2013).

3.29 "The reports produced by Linc Energy and Carbon Energy are amongst the most thorough compilations of information on any UCG pilot trials to date. A great deal of useful information and lessons are incorporated into the reports. It is not possible to do justice to the quantity of technical information provided by each of the companies in a summary set of recommendations. No doubt, over time, the companies will see fit to release at least some of this technical information into the public domain so that others are able to make their own assessments of the merits and risks associated with UCG."

3.30 Additionally, a failure to engage the public and comply with regulatory requirements and ultimately failure to deliver a viable demonstration for investors has thus far, outside Uzbekistan, prevented confident, long-term delivery of high-performing UCG. And from that latter site, the absence of data means that the story, and of particular relevance here, its environmental, health, safety and community facets, cannot be understood and evaluated.

3.31 Osborne and Gupta (2013) reported that there was, in 2011, an identification by industry experts given price and technology trends that UCG was, again, ready to take off and demonstrate its value, partly because of CRIP developments. Events from 2012-16 appear to have set this back significantly.

3.32 Technology developed in South Africa in the 1950s and thereafter had led to various coal to liquids ( CTL), gas-to-liquids ( GTL) and high-temperature Fischer-Tropsch ( HTFT - improvements of the original 1920s process created in Germany for making synthetic fuels at c 300°C, with an iron catalyst) processes which produced "ultraclean gasoline" (diesel), petrochemicals and oxygenated chemicals, including transport fuels in the SASOL facilities. Coal derived fuels have seen significant growth in China too. The China Shenhua Group pioneered CTL projects e.g. in Inner Mongolia. A number of Chinese/South African collaborative projects have been progressed and a programme of works is in place for projects in the 2015-20 period. (see also Annex 3.)

3.33 Full lifecycle is generally poorly articulated and detailed. Full life cycle is taken to mean from scoping mapping through exploratory drilling, through production to completion, decommissioning and abandonment, including the long term reassurance visiting of the site or its capped former access wells and air, water, soil testing and testing too of liabilities management where failures have occurred etc. Considerably more is known of the front end of the life cycle than the latter components.

3.34 Interestingly, perhaps, only the Polish research and coal industry community seem to be continuing relevant detailed work, under the HUGE2 (Hydrogen oriented UCG programme, see Annex 3) and related EU programme banner, including test gas analyses and examinations of the cavities produced by UCG processes and the most accessible materials have been presented at international coal conferences, e.g.
This work highlights somewhat unexpected gas characteristics - very high nitrogen product with hydrogen and methane content lower than many tests - and pollution potential of combustion processes but, significantly has involved post-combustion cavity and seam analysis and is focussed now primarily on hydrogen production rather than methane and is only just beginning specifically to explore environmental performance.

3.35 The (2001) report of the then DTI's Cleaner Coal Technology Transfer Programme/ ETSU, "Review of Underground Coal Gasification Technological Advancements is a wide-ranging overview of the technology issues and developments to that time by Creedy et al. (2001). [Interestingly this is just one of 7 reports produced between 1999 and 2009 into UCG in the UK and Scottish context]. It outlines methods and a series of the learnings from case histories at that time, including for El Tremedal. It also summarises environmental impacts and commercial issues as well as providing a view on future R&D directions. Much of this agenda remains to be tested and although the Australian demonstrators were designed with some of these attributes in mind, they have not yet been fully or, successfully, addressed.

3.36 Summary

A large number of sites have tested and piloted aspects of UCG technology worldwide over more than 60 years. Technologies have been developed that allow drilling into coal seams and coal combustion, gas extraction and processing of syngas. No operation has been demonstrated and operationalized in a context directly comparable with the FoF. Nor has any site been closed off after fully successful operation and independently assessed with reference to a robust, or any, ex ante assessment of expected impacts say on groundwater and surface environmental condition. Very little useable data appears to be available demonstrating the hazards, mitigation and results of the successful operation of a UCG/syngas system facility. Those data would ideally connect ex ante statements and expectations therefore with real results across all relevant facets of the UCG operation including environmental, health, seismic, community engagement etc. issues in practice.


Aghalayam, P. (2010) Underground coal gasification: a clean coal technology, in: Handbook of combustion, Wiley-VCH, New York, pp. 257-275.

Andrianopoulos, E, Korre, A and Durucan, S. (2015) Chemical process modelling of underground coal gasification and evaluation of produced gas quality for end use . Energy Procedia 76, 444-453. Presented at European Geosciences Union General Assembly 2015 Division Energy, Resources and Environment.

Blinderman MS & Jones RM (2002) The Chinchilla IGCC Project to Date: Underground Coal Gasification and Environment. Paper to Gasification Technologies Conference, San Francisco, USA, October 27-30 th , 2002.

Boothroyd, IM, Almon, S, Qassim, SM, Worral, F and Davies RJ (2016) Fugitive emissions of methane from abandoned decommissioned oil and gas wells Science of the Total Environment v 547, 15 March 2016, p 461-9

Burton, E., Friedmann, J., and Upadhye, R. (2007) Best Practices in Underground Coal Gasification. Lawrence Livermore National Laboratory, USA.

Creedy DP, Garner, K, Holloway, S, Jones, N and Ren, TX (2001) Review of Underground Coal Gasification Technological Advancements. Report No. COAL R211, DTI/Pub URN 01/1041. DTI/Crown Copyright. ( BGS, Nottingham University and Wardell Armstrong)

DTI (2005) Directional drilling in coal, in: Technology Status Report, DTI, Cleaner Fossil Fuels Programme, pp. 28.

FoEI (2016) Fuelling the Fire: the chequered history of Underground Coal Gasification and Coal Chemicals around the world.

Green, M.B. (1999) Underground Coal Gasification - a joint European Field Trial in Spain. ETSU Report No. COAL R169. DTI/Pub URN99/1093

Green, M. (2008) Underground Coal Gasification, State of the Art. From Proceedings of Clean Coal Conference 2008. Bedewo, Poland, 8 December 2008.
(Presentation att:)

Also in Green M (2009) Overview of worldwide field activity and the future of UCG. In: Proceedings of the 4th international underground coal gasification conference. London, UK, 10-11 Feb, 2009. Woking, Surrey, UK, The UCG Partnership, 33 pp

Khadse, A, Qayyumi, M, Mahajani, S, Aghalayam, P. (2007) Underground coal gasification: A new clean coal utilization technique for India, Energy, 32, 2061-2071
Lavis, S, Courtney, R and Mostade, M (2013) Underground Coal Gasification. Chapter 8 in Osborne, D, The Coal Handbook. pp226-239

Mallett, C. (2015) Underground Coal Gasification: an Overview of an emerging coal conversaion technology. CornerStone 3 (2) 56-60

Moran, PC, da Costa PJ and Cuff EPC, (2013) Independent Scientific Panel Report on Underground Coal Gasification Pilot Trials. Queensland State Independent Scientific Panel ( ISP) on Underground Coal Gasification: Queensland, Australia.

Osborne, D (2013) (Ed.) The Coal Handbook - Towards cleaner production Vol 1, Woodhead Publishing, Cambridge. ISBN 978-0-85709-730-9.

Osborne, DG and Gupta SK (2013) Industrial uses of coal. Chapter 1 in Osborne D (Ed) (2013) DOI 10.1533/9780857097309.1.3

Sajjad, M and Rasul, MG (2014) Review on the Existing and Developing Underground Coal Gasification Techniques in Abandoned Coal Seam Gas Blocks: Australia and Global Context Conference Proceedings Paper - Energies "Whither Energy Conversion? Present Trends, Current Problems and Realistic Future Solutions" from First International e-Conference on Energies 14-31 March 2014

Shafirovich, E. and Varma, A. 2009. Underground coal gasification: a brief review of current status. Indust.Eng.Chem.Res., 48, 7865-7875.

Stanczyk, K. Kapusta, K, Wiatowski, M, Swiadrowski, J, Smolinski, A, Rogut, J, Kotyrba, A. (2012) Experimental simulation of hard coal underground gasification for hydrogen production, Fuel, 91, 40-50.

Walker, L.K. (1999) Underground Coal Gasification: A Clean Coal Technology for Development. The Australian Coal Review, October 1999, 19-21.

Wiatowski, M, Stanczyk, K, Swiadrowski, J, Kapusta, K, Cybulski, K, Krause, E, Grabowski, J., Rogut, J, Howaniec, N, Smolinski, A. (2012) Semi-technical underground coal gasification ( UCG) using the shaft method in Experimental Mine "Barbara", Fuel, 99 170-179.

Wilks I.H.C. (1983) The cavity produced by gasified thin deep seams. Proceedings of the 9 th Underground Coal Gasification Symposium. US DoE Report DoE/METC84-7, 314-322.

Younger, PL and Gonzalez, G (2010) The groundwater hydrology of underground coal gasification coupled to carbon capture and storage. British Hydrological Society Third International Symposium, Managing Consequences of a Changing Global Environment, Newcastle 2010.


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