Underground storage of sales quality gas is a technique widely used to better manage variations in consumer demand.
Sales gas is stored in depleted gas reservoirs below the Moomba plant in northeastern South Australia.
Subsurface geological conditions which may be suitable for underground gas storage have been identified in the Two Wells - Port Wakefield area of the Northern Adelaide Plains. This area is within 100km of Adelaide.
The establishment of ~10 PJ of gas storage in the Adelaide area, which would provide approximately three weeks average supply, would have the following benefits.
- greater flexibility in operations of the Moomba-Adelaide pipeline
- a reduction in gas field operating costs
- facilitation of competition in gas supply
- assistance in reducing gas prices
- allow greater competition in electricity supply both locally and interstate
- greater physical security of supply.
Attempts during the 1980s to define potential areas for shallow gas storage near Adelaide were abandoned when no suitable Tertiary host rocks were found.
Work in 1995 has identified an area bordering Gulf St Vincent on the Northern Adelaide Plains where relatively undisturbed Cambrian rocks occur at depths of interest for gas storage (~500 m).
Rocks of this age are not currently exploited for underground water in the Two Wells-Port Wakefield area and it is likely that any contained water is saline.
The location of suitable sites for gas storage in yet to be defined structures as opposed to existing depleted fields is highly speculative and requires much further geoscientific work.
Suitable reservoirs, overlying sealing strata and gas trapping mechanism, must be identified and tested to ensure that gas can be safely stored and economically produced.
The Department of State Development (formerly Primary Industries and Resources, South Australia) assembled a package of technical data on the storage possibilities of the Northern Adelaide Plains to attract private sector investment.
The Department introduced amendments to the Petroleum and Geothermal Energy Act 2000 to ensure appropriate licensing and regulation of gas storage exploration and development activities.
If exploration for gas storage is undertaken in the area, the initial program is likely to involve seismic surveys using mainly existing roads for access plus the drilling of several wells to ~1 000 m. The exploration program could take three years.
If these results are positive (ie. a sealed reservoir is located), testing would be necessary to determine integrity of seal to ensure no risk of gas leakage.
Any development of gas storage would involve the laying of underground pipelines, drilling of a small number of gas injection and withdrawal wells, and construction of surface facilities for dewatering and compression of the gas.
The total area occupied by wells and surface facilities is likely to be of the order of a few hectares, although the gas storage accumulation in the subsurface could extend over 2 km².
Before any approval to develop gas storage is granted, a thorough hazard analysis would be required such that any public safety risks could be identified and quantified.
This analysis would be made available for public comment and those comments taken into account before any approvals are considered.
Click here to view a thesis on the gas storage potential of the Stansbury Basin (University of Adelaide): http://web2.library.adelaide.edu.au/theses/09SM/09smr8884.pdf