Environmental Engineering Reference
In-Depth Information
and Northern Ireland will require the operators to put in place procedures
to ensure that there is no future release or escape of shale gas or waste
water either into the environment or into groundwater-bearing strata.
3 UK Estimates of Shale Gas
In the UK, the government Department of Climate Change (DECC) defines
the estimates of gas in the following terms:
Proven: reserves which, on the evidence available, are virtually certain to be
technically and commercially producible, i.e. have a better than 90% chance
of being produced.
Probable: reserves which are not yet proven, but which are estimated to
have a better than 50% chance of being technically and commercially
producible.
Possible: reserves which at present cannot be regarded as probable, but
which are estimated to have a significant but less than 50% chance of being
technically and commercially producible.
Terminology referring to smaller physical scales is also used. Gas Initially
In Place (GIIP), or Gas In Place (GIP) for the remainder if production has
commenced, refers to the total gas resource that is present in a reservoir
or gas field and is a resource rather than a reserve measure. Estimated
Ultimately Recoverable (EUR) refers to a given well or field over its lifetime
and accounts for its production to date and anticipated recovery. This
measure is closer in sense to a reserve.
The British Geographical Survey (BGS) in association with the Department
of Energy and Climate Change (DECC) completed an estimate for the
resources (gas in place) of shale gas in part of central Britain in an area
between Wrexham and Blackpool in the west, and Nottingham and
Scarborough in the east.
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The estimate is in the form of a range in order to
reflect geological uncertainty. The lower limit of the range is 822 trillion
cubic feet (tcf) and an upper limit of 2281 tcf, but the central estimate for the
resource is 1329 tcf (see Figure 6).
This shale gas estimate is a resource figure and so represents the gas that
is thought to be present, but not the gas that it might be possible to extract.
Prediction of reserves then needs to be considered against what can be
economically recovered, which of course depends on the price of gas within
the market it is operating in. The volumes of gas that can be actually re-
covered against the predicted reserves are very dicult to determine until
exploratory wells have been drilled. While figures of between 10 and 20% of
predicted reserves could be recoverable, in some instances the gas actually
recovered has been very much lower.
In terms of estimates from individual licence areas that have already been
allocated in the UK, four companies have provided estimates of reserves but
to date only one company, Cuadrilla Resources, has carried out exploratory
drilling. This exploration of the commercial shale gas extraction has taken
place in the Bowland Shales in Lancashire. The company's UK Petroleum
