Large field increases Queensland gas supply

Where Santos Combine is Expanding Gas Reserves [82,,239 bytes] The Santos Group led combine in Southwest Queensland Cooper basin has recorded one of the best exploration success rates in Australia's onshore drilling history. As of mid-November with 5 wells to drill, the company had a 77% success rate in its 2 year, $150 million (Australian) Accelerated Gas Exploration Program, begun in early 1996. Designed mainly to confirm and add reserves on blocks in Southwest Queensland, the program has

Dec. 15, 1997

3 min read

Where Santos Combine is Expanding Gas Reserves [82,,239 bytes]

The Santos Group led combine in Southwest Queensland Cooper basin has recorded one of the best exploration success rates in Australia's onshore drilling history.

As of mid-November with 5 wells to drill, the company had a 77% success rate in its 2 year, $150 million (Australian) Accelerated Gas Exploration Program, begun in early 1996.

Designed mainly to confirm and add reserves on blocks in Southwest Queensland, the program has hiked reserves 39% this calendar year alone to 2 tcf in mid-November from 1.47 tcf at the end of 1996.

With this success behind it, Santos has extended the program through 1998, and there is every prospect of renewal beyond that.

In 1996, 18 wells were drilled for 14 successes. This year (through end October) another 21 wells were drilled for 16 successes plus two geological successes that led to other targets. Seven 1997 successes found new fields. The rest were appraisals.

Encouraged, Santos slated 20 or so wells for 1998, when three rigs are to work full time.

Barrolka field grows

By far the province's largest field is Barrolka. Originally discovered in 1976 in an area operated by farminee Australian Aqui- taine, Barrolka is now estimated to have 6.45 tcf of proved and probable gas. That makes it Queensland's largest conventional gas discovery (as opposed to coalbed methane) and Australia's largest onshore gas 'discovery' since 1971.

The reserves were determined this year in a 6 well program that began by targeting what were first thought to be separate culminations surrounding the original 1976 discovery. The new wildcats-Beeree, Coo- lah, and Barrolka North East-were successful. An appraisal well drilled in each indicated all were connected to Barrolka in one large complex geological feature.

Santos believes it has a further 930 bcf of gas reserves over and above these commitments, and the group is actively seeking new markets in Queensland and New South Wales. It believes the plant-pipelines infrastructure gives it an advantage over other suppliers. Several exploratory prospects remain.

Barrolka reserves are based mainly on the Permian age Toolachee formation reservoir, but there is scope for more gas in other Permian Cooper basin sediments on the structure.

In another example of the program's expanding potential, success in the recently completed Whanto 1 wildcat has opened up a number of undrilled possibilities in the northern sector of the Southwest Queensland permit. Also, recent drilling suggests new reserves can be added in Wackett gas field.

Seismic acquisition shows increasing emphasis on 3D surveys. The group is acquiring 1,500-2,500 km/year of seismic data. It shot 300 sq km of 3D data in 1996 and 500 sq km this year. Up to 1,000 sq km are planned in 1998.

Overall the Santos group is taking a bullish view of the future. The uprated Ballera gas centre is already catering for gas contracts to South Australia and southeast Queensland. Currently the plant is undergoing new expansion to meet a recently won contract to supply gas to Mt. Isa and other new projects in the Northwest Queensland mineral belt.

Interests in the South West Queensland Unit are Santos Group 58.8625%, Delhi Petroleum 23.2%, Boral Energy Resources 16.5%, Gulf Australia Hydrocarbons Ltd. 1.2%, and Oil Co. of Australia 0.2375%.