Memorandum from Professor Peter Hall,
University of Strathclyde and Mr Stephen Jewell, Composite Energy
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
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
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
In comparison with the proposed sequestration
of CO2 in offshore oilfields, this proposal has a number
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
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.
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 recoveryalready completed
Paper and laboratory exercise to
rigorously test cores and develop optimum drilling tactics and
Initial testing of flue gas injection12-18
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 areathis 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
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:
Vertical well to secure core data £250,000
Desktop design / feasibility study £200,000
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
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