Feature Article - Yolla gas field (Tasmanian Year Book, 1998)
Contributed by Mineral Resources Tasmania
Tasmania is the only Australian State which does not have a source of piped natural gas available to its population and industrial base. Natural gas is the fastest growing energy source in Australia and would provide effective competition to electricity for a range of industrial and domestic services. Natural gas, in the raw state, contains the retail gas (methane) and liquid petroleum gas (propane and butane). A significant gas resource, rich in light hydrocarbons and liquid petroleum gas (LPG), lies off the Tasmanian coast in the Bass Basin, awaiting development.
The Bass Basin is located under the waters of Bass Strait, between Tasmania and Victoria, and is bounded to the east by Flinders Island and to the west by King Island. In 1985 a consortium headed by Sagasco Resources Ltd undertook a major exploration effort in this region. One of the successes of the exploration program was the discovery of the Yolla oil, gas and light hydrocarbon field. The Yolla structure is approximately 135 km north of Burnie in water 79 metres deep.
Yolla is interpreted as a complex structure which has formed as the result of a tectonic history of interrelated subsidence and compression. If commercial operations started at Yolla, it would yield a mix of assorted hydrocarbons including methane, propane, butane and a light type of crude oil.
Since the initial exploration, there has been additional seismic interpretation over the entire Bass Basin, which has considerably enhanced the prospectivity of the area. In February 1994, the acquisition of 3D seismic data over the Yolla field commenced and took approximately one month to complete. In conjunction with the 3D seismic survey, the Joint Venture undertook an aeromagnetic survey of the field and integrated the results of the 2 surveys to better define the Yolla structure. The Joint Venture has spent in excess of $3 million on these surveys to date.
For production to proceed, 3 holes need to be drilled to verify whether or not there are commercial quantities of gas. The exploration and retention licences held over the area have changed several times and are currently held, in the case of Yolla (T/RL1), by a consortium led by Boral Energy Resources Limited.
The major deterrent to further exploration and development of the Yolla field has been the lack of a guaranteed market for the gas. The size of the development required to bring gas ashore is too large for the Tasmanian market, without a new major industrial user. The consortium is continuing their efforts to secure such a market, either in Tasmania or on the mainland.