Home' Australian Resources and Investment : September 2009 Contents AUSTRALIAN RESOURCES & INVESTMENT • SEPTEMBER 2009 • 43
focus: coal seam gas
a poor appreciation of the local and regional geology, effect of stress
regimes on coal permeability, inappropriate well completion methods, as
well as cost contributing to the failure. This early unsuccessful phase is
well documented by Riley (2004).
The first commercial production in Australia was achieved by BHP in
February 1996 from within the Moura Mine Leases covering the Late
Permian Baralaba Coal Measures of the eastern part of the Bowen Basin.
Production averaged 4 terajoules (TJ) per day and was piped to
Gladstone. This project is now operated by Anglo Coal (Moura) Ltd.
Commercial production in the Sydney Basin began in April 2001, when
Sydney Gas Ltd, which had been exploring Permian coals of that Basin
since 1998, supplied CSG to the Sydney market.
During the 1990 s, Oil Company of Australia (OCA) (now a subsidiary
of Origin Energy Ltd) acquired Conoco s interests in the Moura-Dawson
Valley area of the eastern Bowen Basin. The Baralaba Coal Measures in
this area contain an aggregate of 30m seams of coal with gas contents
of 9-25m3/tonne on a dry ash free basis (DAF) at depths of 300m to
1000m. However, permeability is adversely impacted by high
compressive stress and mineralisation in cleats and fractures. Conoco s
experience had demonstrated that concepts applicable under these
conditions in the Black Warrior Basin in the USA were not valid here.
OCA S focus on understanding the local geological setting and stress
regime together with improvements in drilling and well completion and
better cost control resulted in modest success with current estimated
production of 5.5 PJ per year (Baker and Slater, in press). Factors that
reduce and/or destroy permeability in the Moura-Dawson Valley region
continue to inhibit CSG production in the Gunnedah and Sydney Basins
in New South Wales. The Moura-Dawson Valley operations are now
owned by Anglo Coal (Moura) Ltd in joint venture with Mitsui Moura
Investments Pty Ltd, with Molopo Australia Ltd holding a 50% interest
in some areas.
Western areas of the Bowen Basin have proven to be more
favourable for commercial CSG production. In 1989 at Fairview, Tri-Star
Petroleum Pty Ltd identified the potential of the Comet Ridge which is
characterised by low structural stress. At Fairview, the Bandanna
Formation (a correlative of the Baralaba Coal Measures) has 5m to 11m
of coal with high gas content (10-15m3 per tonne) at depths ranging
from 500m to 800m and permeabilities exceeding 50 millidarcies.
Production of the first sales gas occurred in 1996 when an estimated
1PJ was produced that year. Fairview CSG Field has large reserves and is
now jointly owned by Origin Energy Ltd (23.93%), Santos Ltd (36.07%)
and PETRONAS (Petroliam Nasional Berhad) of Malaysia. The field was
producing at an annualised rate of just over 26PJ in 2008. Spring Gully
Gas Field is a similarly large field that occupies the southern portion of
the Comet Ridge Anticline and shares the geological setting of Fairview.
Origin is the operator and production from the field began in June
2005. To the east, coals of the Baralaba Coal Measures of Burunga
Anticline are highly fractured and display good permeability. The
Burunga Anticline hosts two large fields. Scotia in the north is owned
by Santos and began production in May 2002. Peat CSG Field, to the
south of Scotia, is operated by Origin and commenced delivering CSG to
markets in February 2001.
In the northern Bowen Basin, the Late Permian Rangal Coal
Measures (a correlative of the Baralaba Coal Measures and the Bandanna
Formation) and the older Moranbah Coal Measures, German Creek
Formation, Collinsville Coal Measures and more recently, the Fort Cooper
Coal Measures have been explored for CSG. The main target has been the
Moranbah Coal Measures which have 2 to 4m seams with a net
Fig. 2. Eastern Australian Gas Reserves by Sedimentary Basin (source RLMS,
Fig. 3. Eastern Australian Coal Seam Gas Reserves by Company (source RLMS,
Fig. 4. Coal Seam Gas Reserves at December 31 2008 (source RLMS, 2009)
Fig. 5. Aerial view of Tipton West CSG Field showing dam for by-product water
and compressors (Arrow Energy photo)
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