Select Committee on Science and Technology Written Evidence


Memorandum from Professor Peter Hall, University of Strathclyde and Mr Stephen Jewell, Composite Energy Ltd


  This paper asserts that one key solution in order to assist the UK comply with its obligations under the Kyoto agreement is to commence the long-term disposable of CO2 into unminable coal measures as soon as possible.

  We wish to draw to attention of the Science and Technology committee to the following recent developments in the recovery of coalbed methane and CO2 disposal in coal:

    —  Composite Energy have recently deployed horizontal borehole drilling technology in a deep, unminable Scottish coal reserve close to Longannet power station (the second largest in the UK).

    —  Significant amounts of natural gas are currently being released from this initial test borehole providing a potential new energy source.

    —  Recent research at Strathclyde University has shown that Scottish coals can permanently store CO2, unlike some test coal measures in North America.

    —  The Scottish coals have the capacity to store more CO2 than is generated from the combusted natural gas released from the coal.

    —  Therefore, coal has the capability to be a clean energy source and a net extractor of carbon from the environment.

    —  We calculate that coal has the potential capacity to provide all of the UK's future CO2 storage needs to meet the Energy White Paper targets.

    —  Underground CO2 disposal from Longannet power station in Scotland (the second largest in the UK) could commence in 2006-07.

    —  It is estimated that there are 120 million cubic metres of unminable coal (coal over 3,000 ft under the earth) close to Longannet and significantly more in the extended geological basin.

    —  In comparison with the proposed sequestration of CO2 in offshore oilfields, this proposal has a number of advantages:

      —  There is no need to construct expensive and dangerous amine scrubbers to purify CO2 from flue gas. The approval for construction of one such apparatus would take a minimum of four years, followed by a similar period for design, construction and testing. The disposal of spent amines is in itself expensive.

      —  There is no need to design and construct hugely expensive sub-ocean high pressure CO2 pipeline infrastructure.


  Recent research into coal/CO2 interactions in the Department of Chemical and Process Engineering in the University of Strathclyde have shown that the bituminous coals that constitute most of the resource of the UK have the ability to permanently store CO2. Technically, the activation energy for release is so high that the gas remains permanently trapped at the temperature of normal coal deposits. Methane has a much lower activation energy for release and diffuses out of coal spontaneously. This makes coal a very attractive medium for CO2 disposal. Approximately 4-6 molecules of CO2 are absorbed for the release of one methane molecule. Thus, valuable methane gas can be produced with a net reduction in green house gas.


  The extraction of coalbed methane and the possibility of storage of CO2 have been investigated in a number of projects in North America.[2] It has been widely thought that this technology is unsuited to the UK because British coals have much lower permeabilities than their North American counterparts.


  The development of new technology particularly in the area of horizontal drilling is about to radically change the commerciality of coal bed methane in the UK. Horizontal wells have now been drilled all over the world in the oil and gas sector and some of the most challenging of these have been achieved offshore in the UK. The technology behind these wells was once prohibitively expensive for marginal onshore developments but this has changed markedly over the last five years. Horizontal drilling is now being employed in Australia and the US in coal for the first time to develop more marginal CBM plays where the coals may be thin or of low permeability. Essentially a horizontal well can achieve a much greater exposure of coal than a vertical well by increasing the area of coal available for flow. This leads to higher production rates and an accelerated depletion of the gas within the coal. Both factors significantly improve the commerciality of coal bed methane developments. In the UK horizontal well technology is being deployed in coal for the first time in the central belt of Scotland under the DTI's licence PEDL 133.  This will be done in an area previously drilled with vertical wells and where natural gas production has been previously demonstrated. If successful, production rates are expected to more than double and a significant new source of indigenous natural gas will have been unlocked.


  The initial horizontal drilling site is close to Longannet power station, the second largest in the UK. It is estimated that there are over 120 million m3 of unminable coal in the vicinity of Longannet power station (figures from an anonymous and confidential source). Our calculations show that if fully deployed, local coal resources could store all of the CO2 released from Longannet for the next 20 years. Realistically however, it should be possible to reduce CO2 emissions from Longannet by 30%.


  Research has also shown that the affinity of coal for CO2 is much greater than for N2.  Therefore, it is not necessary to separate or purify the CO2 from the Longannet stack (the composition of flue gas is approximately 15% CO2, 85% N2). Indeed, the presence of N2 is necessary to assist the diffusion and absorption of CO2.  It should be possible to dispose of flue gas with minimal processing and possibly in its raw form.


  The time scale for deployment of technology would be as follows:

    —  Initial horizontal drilling with gas recovery—already completed

    —  Paper and laboratory exercise to rigorously test cores and develop optimum drilling tactics and methodology—6-12 months

    —  Initial testing of flue gas injection—12-18 months

    —  Scale-up—18-24 months.


  A project to demonstrate the feasibility of CO2 disposal in coal would consist of two Phases.

    —  The first phase would be to gather data from actual core in the proposed trial area—this would involve drilling a simple vertical wellbore and taking rock and coal samples. A desktop study would then be performed to predict the performance of horizontal injection and production wells to optimise their placement and to assess any surface processing requirements.


    —  The second phase would be to drill to horizontal wellbores into the coal, one to inject flue gas and the other to produce natural gas. Minimal surface facilities would be anticipated. If the field trial proved successful the scheme could be rapidly extended by simply drilling new wellbores every square kilometre extending in a simple pattern away from the power station site. The directional nature of horizontal drilling allows for a great deal of flexibility when it comes to selecting surface drilling locations.


  The costs of securing the necessary data and deploying an actual twin wellbore disposal scheme would be £2.5 million broken down as follows:

Phase 1
  Vertical well to secure core data  £250,000
  Desktop design / feasibility study  £200,000

Phase 2
  Drilling two horizontal boreholes  £1,000,000
  Surface injection facilities  £600,000
  12 month field trial operating costs  £450,000
  Total Estimate  £2,500,000

  Phase 2 would be contingent on the results of Phase 1 (Data gathering and Feasibility Study).

  No allowance has been made for income generated from the natural gas generated and sold nor for any CO2 disposal credits.

September 2005

Burlington Resources:  Allison Unit, St Juan Basin, New Mexico, USA
BP-Amoco:  Tiffany Unit, St Juan Basin, Colorado, USA

2   Alberta Research Council: Fenn-Big Valley Pilot Study, Alberta Canada Back

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