IN WESTERN AUSTRALIA - Department of Mines and Petroleum

underlain by a 10 m gross oil column at the top of
the Birdrong Sandstone.
Crosby 1
The Crosby field, located in WA-12-R and operated
by BHP Billiton Petroleum, is situated 106 km westnorthwest
of Onslow. Crosby 1 penetrated 7 m of
gas overlying 36 m of oil in the Pyrenees Member
of the Lower Barrow Group in a complex structural
trap between the Scafell Trend and the Novara Arch
in the Exmouth Sub-basin.
Ravensworth 1
Ravensworth 1 was drilled in WA-155-P,
approximately 108 km west-northwest of Onslow.
The well encountered a 44 m gross hydrocarbon
column consisting of 7 m of gas and 37 m of oil in
the Pyrenees Member sands.
Browse Basin
Within the Browse Basin, four exploration wells were
drilled: Ichthys 1, Ichthys Deep 1, Maginnis 1 and
Strumbo 1, with Ichthys and Ichthys Deep both
intersecting thick zones of gas pay. Neither
Maginnis nor Strumbo intersected any
hydrocarbons. An appraisal well, Ichthys 2, was
drilled to assist in determining the extent of the
Ichthys gasfield.
Ichthys 1 and Ichthys Deep 1
These wells were drilled by Inpex in their 100%
owned permit WA-285-P. The wells encountered
excellent gas shows in their target horizons and
follow-up gas discoveries at Gorgonichthys,
Dinichthys and Titanichthys made in 2002.
Bonaparte Basin
The only well drilled in the Bonaparte Basin was
Weasel 1 by Woodside Energy in WA-279-P. The
well did not intersect any hydrocarbons and was
plugged and abandoned.
PETROLEUM RESERVES AND RESOURCES
Petroleum reserves in Western Australia have been
compiled under two main headings – ‘developed
fields’ and ‘undeveloped fields’. Developed fields are
those currently producing fields that are located
either offshore in Commonwealth or State Waters or
onshore within Western Australia. The reserves
quoted are remaining reserves as at 31 December
2003. Undeveloped fields have reserves associated
with the static petroleum resources that may be
developed in the future.
In all of the above categories, reserves or resources
have been quoted at the 90% and 50% probability
of recovery levels (P90 and P50).
The reserves for undeveloped fields are the
reserves associated with the static petroleum
resources that may be developed in the future.
Undeveloped fields have been subdivided into three
categories as follows:
• Category 1, Potential for early development
• Category 2, Expected medium to long term
development
• Category 3, Not currently viable; subject to
Retention Lease
The overall reserves and production figures for
Western Australia up to 31 December are listed
in Table 1.
EXPLORATION ACTIVITY
(Compiled from data provided by companies; where
there is no report for a company, it is due to them
not submitting a report)
Apache Energy
In the calendar year 2003, Apache operated 18
exploration wells, 11 appraisal wells and 4
development wells. Three field discoveries were
confirmed and all appraisal wells but two and all
development wells were successful.
Taunton 3 and 3ST (TL/2) were to confirm the
easterly extent of the field. Both wells encountered
oil-bearing reservoir section of similar thickness and
quality to the discovery well, Taunton 1 drilled in
1991.
Thomas Bright 1 and 2 (WA-214-P) were drilled to
establish the presence of gas-bearing sands over
the southern portion of the John Brookes-Tryal
Rocks Anticline. Both wells encountered the main
pay section seen at John Brookes 1 and both were
gas bearing. Deeper gas-bearing sands were also
encountered at Thomas Bright 1. The outcome of
these wells in combination with John Brookes 1 has
led the WA-214-P participants to proceed with the
development of the field.
North Pedirka 1 (TL/1) was drilled from the Victoria
Platform and encountered an 8 m gross oil column
in the massive Flag Sandstone. The well was
immediately completed and brought on production.
Ginger 1 well was drilled to evaluate a Biggada
prospect identified by bright seismic amplitudes.
Table 1. 2003 Production and reserves for Western Australia
PWA April Edition - 2003 Review 11
The well encountered a 21 m gross gas column
within a tight sandstone reservoir. No gas/water
contact was encountered. The commercial viability
of Ginger remains uncertain pending the analysis of
reprocessed seismic data.
Apache expects to drill more than 35 wells during
2004. Exploration activities will comprise more than
20 wells and be mainly concentrated in the Varanus
Island and Dampier areas. A highlight of the year will
be Blackdragon 1 in the Exmouth Sub-basin (WA-
335-P). This well is situated in over 1400 m of water
and is Apache’s first deep water well in Australia.
Arc Energy
ARC Energy participated in the drilling of 14 of the
77 wells drilled in Western Australia in 2003 and
operated seven of these.
2003 Exploration Highlights
Exploration drilling at Eremia 1, in the onshore
resulted in a commercial oil discovery at Eremia.
Offshore, the Twin Lions 1, Mentelle 1 and Vindara
1 wells were unsuccessful.
The Hibbertia 3D seismic survey identified a number
of gas prospects east of the Hovea oilfield and north
of the Beharra Springs gasfield that will be drilled in
2004. Preparations are underway for the acquisition
of the Denison 3D seismic survey over the eastern
oil fairway in L1/L2, and land gravity data has
already been acquired over this oil fairway.
BHP Billiton Petroleum
Outer Browse Area
BHP Billiton regards the deep water Outer Browse
Basin as a frontier basin with high potential and
little prior exploration.
In 2000, the company was awarded five blocks:
WA-301-P, WA-302-P, WA-303-P, WA-304-P and
WA-305-P. These blocks comprise around
25 000 km 2 and lie in water depths ranging from
1000 to 3000 metres.
Category Oil (GL) Condensate (GL) Gas (Gm 3 )
Developed Fields
2003 Production 14.054 6.606 27.435
Remaining Reserves P90 33.449 51.968 462.253
P50 60.015 75.757 592.933
Undeveloped Reserves
Category 1 P90 36.681 38.295 214.656
P50 54.057 55.871 304.145
Category 2 P90 8.900 3.400 31.750
P50 13.300 7.500 62.190
Category 3 P90 4.980 87.509 1530.892
P50 8.660 141.275 2385.666