Two significant discoveries are shaping up off Northwest Australia that could help bolster prospects for long term liquefied natural gas exports from the region.
A group led by Ampolex Ltd., Perth, made a sizable oil and gas discovery in the Carnarvon basin off Western Australia.
In the Timor Gap area, testing ended on BHP Petroleum Pty. Group's 1 Undan wildcat, which apparently found a world class gas/condensate reservoir (OGJ, Aug. 7, p. 37).
Ampolex find
Logs and cores indicated an oil and gas column in high quality sands at 2,248-2,335 m in Ampolex's 1 Wonnich wildcat on the TP/8 permit.
An initial drillstem test at 2,330-33 m flowed 1,040 b/d of oil, 1.1 MMcfd of gas, and 335 b/d of water.
A second test of the same interval gauged 34 gravity oil at a rate of 1,375 b/d plus 1.1 MMcfd of gas and 585 b/d of water. Gas:oil ratio was estimated at 500:1.
A third test of 10 m of perforations at 2,255-58 m and 2,261-68 m flowed gas at a peak stabilized rate of 27 MMcfd through a 1 in. choke. Flow was limited by equipment. Condensate:gas ratio was pegged at 10.7 bbl/MMcf.
Ampolex also reported carbon dioxide content of the find at 4.5 vol %.
The discovery is only 20 km west of Harriet oil field and oil and gas production facilities on Varanus Island. The island lies just west of the Northwest Shelf LNG export complex on Western Australia's Burrup Peninsula.
Interests are operator Ampolex 25%, Apache 22.5%, Kufpec 19.28%, Novus Petroleum 12.5%, Marubeni Oil 12.22%, Hardy Petroleum 8.4%, and New World Oil & Developments 0.1%.
BHP discovery
BHP's preliminary estimate of Undan reserves is 1.5-4 tcf of gas and 100-250 million bbl of condensate. In addition, BHP sees potential for recovery of natural gas liquids at about 70-175 million bbl of crude oil equivalent.
A test of an interval at 3,097-3,109 m flowed 22.13 MMcfd of gas and 1,639 b/d of condensate through a 3/4 in. choke.
A test of a Jurassic interval at 3,016-21 m flowed 42.24 MMcfd of gas and 2,286 b/d of condensate.
BHP measured a gross hydrocarbon column of 139 m but deemed it unnecessary to test all zones.
The 1 Undan discovery is on Zone of Cooperation Area (ZOCA) Permit 91-12 on the same structure the Phillips Petroleum Co. group tapped last February in adjoining permit ZOCA 91-13 (see map, OGJ, Jan. 2, p. 22). Phillips 1 Bayu flowed from four zones at a combined rate of 90 MMcfd of gas and 5,250 b/d of condensate.
About 60% of the field, as currently mapped, apparently lies under the BHP permit. Bayu and Undan are 10 km apart on a structure that covers an area of 160 sq km.
The hydrocarbons found in both discovery wells lie in reservoirs within a similar geological sequence with the same hydrocarbon-water contact.
Long range options for development range from a project to strip liquids and reinject gas to a full scale LNG project.
Appraisal drilling and additional seismic work will take place on the structure during the next 18 months.
Plans call for moving the rig that drilled the Undan strike to drill the 1 Sandang wildcat between the Undan-Bayu structure and Elang oil field in the Timor Gap.
Interests in the Undan discovery are BHP 42.417%, Santos Ltd. 21.426%, Inpex Sahul 21.209%, and Petroz NL 14.948%.
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