Bord Gais and a handful of multinational corporations are engaged in a complex courtship, involving industrial energy users and the Government, which will frame the future shape of the State's gas infrastructure.

There are proposals to invest more than £1 billion (€1.27 billion) in the Corrib gas field off the Co Mayo coast and a plethora of underground pipelines and sub-sea interconnectors, but the endgame to decide which projects go ahead is just beginning.

Among the various related factors at play, one thing is certain. Rising demand and the depletion of the Kinsale field off Co Cork means capacity on the Bord Gais network will meet demand only until 2004.

For the State-owned company, which wants to expand capacity by building a second interconnector parallel to its existing link between Dublin and Moffat in Scotland, the key question is whether the Government will sanction the £300 million investment that this would require.

Bord Gais is also seeking to spend £200 million building a loop line from Dublin to Galway, onwards to Limerick and then to Cork.

But the fate of these proposals will probably depend on external developments, in particular at Enterprise Oil's Corrib gas field.

If the field proves commercial - and most industry observers believe it will - the Government may be unwilling to release funding to develop a second interconnector to Scotland. In this scenario it is more likely that the State-owned company would be sanctioned to extend its network to Galway, taking gas from the Enterprise field, which would be brought ashore at Pullathomas, Broadhaven, Co Mayo.

In addition to countering a looming shortage of capacity on its Dublin-Cork pipeline, this would also add rural areas to its network.

Meanwhile, Premier Transmission, a consortium owned by British Gas and US energy group KeySpan, wants to build a crossborder interconnector linking the networks in the Republic and North. This would cost £120 million.

Yet another group, US-owned El Paso, has proposed spending more than £100 million on an interconnector between Wales and north Dublin.

Contracts to supply major industrial users of gas - electricity generation plants especially - will be crucial to the viability of these last two proposals.

Whichever groups bring gas into the Republic will also have to secure use-of-system contracts to transport their gas through the Bord Gais network to customers. Possible tariff structures are being reviewed by the Department of Public Enterprise.

Slowly, however, the leading players are beginning to reveal their positions.

Enterprise is expected to announce shortly that tests carried out this week an a new segment of its field have been successful. While Enterprise, in a joint venture with Statoil and Marathon, is not expected to declare that the field is commercially viable until the end of the year, all the signs indicate that it is.

The company has an extensive team working full-time on the project in Dublin and it mounted exhibitions this week along the route of its proposed pipeline between Broadhaven and Galway. This would cost some £100 million, in addition to the £300 million required to bring the gas ashore.

The alternative to the Broadhaven-Galway line is to build a pipeline from Co Mayo to Dublin, estimated to cost more than £120 million. It is probable, however, that this will happen only in the unlikely event that Enterprise cannot agree use-of-system rates with Bord Gais or if the State company's link to Galway is not sanctioned by the Government.

Indications of the Government's thinking have emerged in recent carefully-worded statements by the Minister of State at the Department of Public Enterprise, Mr Joe Jacob, who has overall responsibility for gas.

In an Irish Times interview last April, Mr Jacob said his initial advice was that the "optimal economic measure" would be for Bord Gais to develop a second link to Scotland. He added, however, that "the scene is changing".

Last month, when introducing the a Gas Amendment Bill to the Dail, Mr Jacob said: "If one or other of the private developers is not committed to building the necessary infrastructure by the end of the year at the very latest, I will approve the building a second interconnector by Bord Gais."

However, Mr Jacob told the Oireachtas Joint Committee on Public Enterprise and Transport this week that he was maintaining a "wait-and-see" approach in relation to the Enterprise field. He hoped to have clarity from Enterprise on the viability of its field by the end of the year.

Meanwhile, the head of transmission at Bord Gais, Mr Ger Breen, said this week that the company was pushing ahead with both its proposals, conducting preliminary engineering work.

He conceded, however, the company would have to wait until the end of the year for final approval of the projects.

Such timing, of course, would dovetail with an expected announcement from Enterprise that its field is commercial. Some people with a knowledge of the situation have suggested that the Enterprise knows already that the field is commercial, but that the company is hedging to see what is the outcome of tariff negotiations with Bord Gais.

For Premier and El Paso, trading as Celtic Energy, the task is to secure customers. Premier is investing £1 million on engineering design and environmental impact studies. Its chairman Mr Jim Rooney said this week that various potential clients had expressed interest in doing business with the consortium.

"We need to have these expressions of interest turned into binding precedent agreements, which commit the parties to moving forward."

El Paso, though it has a lower profile, is also believed to talking to various industrial users of gas and Bord Gais.

Negotiations to supply groups proposing to build gas-fired electricity generation stations in the newly liberalised power market will probably boil down to price, which itself will be a function of Bord Gais's transmission tariffs.

One well-placed power industry insider suggested this week that electricity consortia would seek "flexible" pricing structures from gas suppliers. In this scenario, the price of gas would reflect the market price achieved for electricity.

Energy users will be awaiting developments later this year with interest.