Wairakei looks to new well for steam

Press, 16 July 1986, Page 44

Wairakei looks to new well for steam

PA Hamilton The Wairakei geothermal power station is running out of steam. It is hoped that a well being drilled on the field will enable the station to produce at full capacity again. The station’s generation superintendent, Mr Keith Wilson, said the station was about 7 per cent short of steam. It is now running at about 142 megawatts, when it could run at 151 megawatts. The station is a baseload station producing power 24 hours a day, 50 to 51 weeks a year. Mr Wilson said the idea was to keep the turbines full up at all times. A well drilled last year proved "a bonanza,” providing an extra 15 megawatts of power. Before that no new drilling had been done on the steamfield for about 10 years. Old wells gradually run out of hot water and steam.

The new well is being

drilled by the Ministry of Works and Development Mr Wilson said initial results should be known within a week or two.

A geothermal well costs about $1 million to $2 million to drill.

The station, built in 1958, produces power from about 60 wells. Mr Wilson said the station was due to run until about 1998 but with refurbishment could go much longer.

He said the station used only about 10 per cent of the 1500 megawatts of power potential coming from the ground. A D.S.I.R. scientist, Mr Ashley Cody, says one of Rotorua’s geysers has been dormant for as long as 30 hours at a time this winter.

The problem, though not unusual, could be related to heavy geothermal draw-off during the colder weather, he said. Waikorohihi, on the geyser flat area, has

shown a marked change in activity since the beginning of July. Its strong interconnections with Pohutu geyser have caused some concern.

Mr Cody said he had monitored Waikorohihi continuously since 1979 because it was easier to monitor than Pohutu, which had been monitored off and on for about 20 years.

“In the first week in July the geyser showed five or six periods of very long dormancy from seven to 30 hours,” he said.

While the geysers were closely related, the fact that Waikorohihi was unusually dormant did not necessarily mean that Pohutu was the same.

“It means basically that here has been a marked change In behaviour on the flat which has not shown dormancy that long in about two and a half years,” said Mr Cody. Pohutu geyser has, how-

ever, shown a marked change in behaviour since late 1983.

Eruptions had occurred at a rate of about 10 to 15 a day but had now increased to about 25 to 30 a day.

They were shorter eruptions although more frequent, and the energy produced had been a lot less, said Mr Cody. He suspected the problem was related to heavy geothermal draw-off during the winter but said there was nothing unusual in the geysers’ present activity.

Summer would probably see the geysers recharged to their previous level although it was doubtful whether the pressure produced by the geysers could keep up with that recharge.

The unusual behaviour would probably disappear again in September or October.