PEL 6, PEL 427 and PEL 428 are located in the Gunnedah Basin
in northern New South Wales and cover an area greater than
18,000km2. All three permits are located immediately north
and west of Santos’ Narrabri Gas Project and Wilga Park
Power Station in PEL 238.
Comet Ridge first gained interests in PEL 427 and PEL 428
via a transfer of ownership from Strike Energy in 2004. Both
permits have a complex history of equity exchanges through
multiple joint venture and transfer arrangements.
These permits have separate Coal Seam Gas Conventional Oil
and Gas interests.
Comet Ridge acquired Davidson Prospecting in October 2010,
which increased Comet Ridge’s CSG interest in PEL 428
from 20% to 40%.
In June 2012, Comet Ridge announced that it had signed an
Asset Sale Agreement to acquire an interest in PEL 6, and
further interests in PEL 427 and PEL 428 from Petrel Energy
In April 2013, Comet Ridge announced that it had finalised
an Asset Sale Agreement for the acquisition of Petrel Energy
Limited’s interests in PEL 6, PEL 427 and PEL 428 in
the Gunnedah Basin in northern New South Wales.
A summary of Comet Ridge’s interest in NSW tenement
areas is as follows:
Santos and Energy Australia hold the remaining
CSG interests in all three tenement areas. Comet Ridge is
the conventional interest operator. Santos is the CSG interest
The Permo-Triassic Gunnedah Basin forms the central portion
of a much larger Sydney-Gunnedah-Bowen Basin system. The Jurassic-Cretaceous
Surat Basin sequence unconformable overlies the Gunnedah Basin
in the permit areas.
Coal Seam Gas
Three coal seam gas targets have been identified in the northern
Gunnedah Basin including the Cretaceous Bungil Formation,
Triassic Moolayember Formation and Permian Black Jack Group
and Maules Creek Formation. The most promising results to
date have come from the Permian Black Jack Group and Maules
Creek coal sequence where recoverable quantities of commercial
gas have been discovered and are being developed by Santos
in PEL 238, directly south of PEL 427.
Conventional Oil and Gas
Conventional petroleum exploration for oil and gas has been
occurred over the northern Gunnedah Basin since the early
1960’s. While the presence of oil has been noted in
wells drilled in the northern Gunnedah Basin, no commercial
quantities have been identified. Conventional gas resources
have been delineated in three areas; Coonarah, Bohena and
Wilga Park in the northern Gunnedah Basin. Gas has also been
recorded over the Permian sequence of the Gunnedah Basin and
overlying Triassic strata of the Surat Basin. Oil and gas
recoveries indicate an active petroleum system is present
over the northern Gunnedah Basin.
Potential reservoirs include sandstones within the Permian
Black Jack Group and Napperby Formation and Early Triassic
Digby and Watermark Formation. Average sandstone porosities
range between 10-30% at shallow depths and decrease to <15%
at depths greater than 2000m.
Prior to Comet Ridge’s acquisition of interest in June
2012, 3 coal seam gas wells and 12 conventional petroleum
wells had been drilled in PEL 6.
Three CSG exploration wells; Gwydir-1, Milguy-1 and Camurra-2
were drilled between March 2009 and June 2010. Situated in
the southern half of PEL 6, each of these wells was designed
to test the Middle Triassic coals of the Moolayember Formation.
This programme confirmed the consistent widespread presence
and gas content of the Moolayember Formation coals. Depth
of the top of the Moolayember Formation in the southern part
of the tenure area is between 300-800m. Gas content up to
7.3m3/t and net coal over 8m were intersected in Milguy 1.
The future focus for CSG exploration in PEL 6 is the Permian
Maules Creek Formation. Thick Early Permian coals have been
intersected in the southern part of the Taroom Trough by conventional
exploration wells. Most of the coals intersected in the northern
part of the permit area at depths greater than 1500m, which
is generally considered too deep for CSG exploration. Further
exploration is required in the Willow Park area in the south
of the permit area where the Permian interval is interpreted
to be at depths suitable for CSG exploration.
The majority of conventional oil and gas exploration has occurred
in the northern and central part of the tenure area where
most of the 2D seismic has been acquired. 10 wells were drilled
prior to 2000 in the permit area. Minor oil and gas shows
were recorded in several wells, with the most significant
from Willaroo-1 which recovered 2-4bbls of live oil from the
Upper Back Creek Group and bitumen from Toenda-ST1.
8 wells have been drilled in PEL 427 since 1969. 7 wells were
drilled targeting conventional gas resources and 1 well has
been drilled targeting coal seam gas.
Two wells have been drilled in the south east corner of PEL
427, Bellata 1 and Bellata 2, both targeting conventional
gas prospects. Oil staining and a “petroliferous odour”
were recorded throughout the lower part of the Jurassic section
and gas shows were recorded over Jurassic sand intervals in
Bellata 1. Comet Ridge Limited drilled Bellata 2 in 2004 to
further test these intervals. Gas shows were recorded over
the Jurassic Pilliga Sandstone and Purlawaugh Formations.
The Permian coals were intersected at Bellata 1, with over
3.0m of coal intersected in the Hoskisson’s and Bohena
seam equivalent. No testing was undertaken over the Permian
coals at time of drilling. Coals within the Permian sequence
recorded a reflectance value of between 0.51-0.62% indicating
these source rocks lie within the early oil generation window.
Bellata 2 well did not target the deeper Permian coals and
was terminated in the Upper Triassic.
In 2007 103km of 2D seismic was acquired over PEL 427 and
In March 2009, Moree 4 core hole was drilled
in the north of PEL 427 as a twin to Moree 1 well to further
evaluate the CSG potential of the Cretaceous Bungil Formation.
This well was drilled to a depth of 495m and encountered approximately
five metres of coal in the Bungil Formation. Moree 1 well
was drilled as a conventional petroleum well targeting stratigraphic
traps within the Early-Middle Triassic sandstone intervals.
The Triassic Moolayember Formation is approximately 1060m
in depth at this location and was not targeted for CSG evaluation.
Despite not being tested for CSG potential, in PEL 427, the
Permian coals within the Bellata Trough are a prospective
CSG target. The Permian coals identified in Bellata 1 are
believed to be the northern extension of the coal formations
seen in the Edgeroi and Blue Hills wells drilled by Eastern
Star Gas in PEL 238.
Edgeroi-1 and Edgeroi-2 were drilled in PEL238 in the Bellata
Trough directly to the south of PEL 427. Edgeroi-2 was drilled
by Eastern Star Gas in 2010 to evaluate the coals within the
Permian Black Jack Group and Maules Creek Group. The well
intersected over 25m of coal over both coal intervals. The
Hoskissons seam of the Later Permian Black Jack Group had
an average gas content of 5.9m3/t (DAF) while the Bohena seam
from the Early Permian Maules Creek Formation had an average
gas content of 14.2m3/t. Depth to top of coals here is between
800and 1050m. Coals are saturated with good permeability.
Exploration activities in PEL 427 have been focused on better
delineating the extent of the Permian coals in the Bellata
Trough, in the south east of the permit. The focus of future
exploration in PEL 427 will be undertaking further evaluation
of the Bellata Trough for both CSG and conventional hydrocarbons
through seismic acquisition and an exploration drilling program.
An extensive review of the magnetic and gravity
data sets available over the northern Gunnedah Basin completed
in early 2012. This exercise has identified some very promising
new prospects north and north west of the Bellata Trough,
and these now also need to be tested through a combination
of seismic and exploration drilling.
In 2010 Comet Ridge announced it had signed a Binding Heads
of Agreement (HOA) to acquire Greenpower Energy Limited’s
(ASX:GPP) 20% interest in PEL 428, lifting Comet Ridge’s
stake in the Joint Venture to 40%.
Four wells have been drilled in PEL 428 since
1963. Barradine West 1 and 2 were drilled in the southern
part of the permit area as wild cat wells and intersected
Cretaceous-Triassic sequence with no shows. No Permian was
present at either of these locations.
In 2007 103km of 2D seismic was acquired over PEL 427 and
In April 2009, Kurrabooma 1 core hole in the north west of
PEL 428 as the first coal seam gas exploration well in the
permit. The well was drilled to evaluate the CSG potential
of the Bungil Formation. This well was drilled to a depth
of 439m and encountered approximately four metres of coal
in the Bungil Formation. Gas contents were up to 4.1m3/t,
however the coals were undersaturated.
The extensive review of the magnetic and gravity data sets
available over the northern Gunnedah Basin completed in early
2012 has identified some very promising new prospects in the
north of PEL 428, including a better understanding of the
likely extent of the Pilliga Trough. These new prospects need
to be tested through a combination of seismic data acquisition
and exploration drilling.
Comet Ridge is currently carrying out desktop studies of existing
data to better understand the conventional petroleum prospectivity
of the three permits in which Comet Ridge controls nearly
100% of the equity. While the study is not complete, work
carried out to date has generated some potential leads which
will require more work to be undertaken.
CONTINGENT RESOURCE CALCULATION
An initial resource booking was announced on 7 March 2011
for PEL 6, PEL 427 and PEL 428, which was assessed by independent
reserves certifiers MHA Petroleum Consultants LLC of Denver.
This certification confirms the CSG potential of these permits,
with Comet Ridge’s share of these resources presented
Unfortunately since 2011, no operational
activities have been able to be completed on the ground primarily
due to external factors including government restrictions
and policy decisions including a period of moratorium on CSG
activities in NSW and land access issues.
The current approved work program is focussed on community
engagement, environmental studies, groundwater monitoring
and geological desktop studies.
Comet Ridge continues to work with Joint Venture partner and
CSG Operator Santos, to plan the future work programme to
evaluate a number of Permian- aged troughs that have been
identified through the large acreage position in the northern
part of the Gunnedah Basin. Several of these troughs may contain
large volumes of recoverable gas, in similar fashion to the
Bohena Trough just to the south of PEL 427.
These permit areas are strategically located in an area which
has potential to be a major coal seam gas producing province,
with gas to flow south to Newcastle and Sydney to meet an
important part of NSW’s gas needs.
It has been widely documented that a gas supply shortage is
looming in NSW. Retail and industrial customers will suffer
because of minority ideological interests that are opposed
to fossil fuels, who continue to spread fear and mistruths
in the NSW media. The Gunnedah Basin has a large volume of
existing proven and probable gas reserves in the Santos and
Energy Australia’s Narrabri Gas Project, and also large
potential for future gas reserves further north and west in
Comet Ridge held acreage.