Geothermal Steam Pressures At Wairakei Falling

Taupo Times, Volume XIV, Issue 50, 29 June 1965, Page 14

Geothermal Steam Pressures At Wairakei Falling

Some high-pressure turbines at the Wairakei geothermal power plant will probably have to e replaced within the next few years to meet changing underground pressures on the production field.

Bore pressures are steadily dropping throughout the field and this trend is expected to eontinue uiitil .supply to the turbines becomes insufficient for the generation of electricity. There are four highpressure turbines designed to work at a pressure of 180 pounds to the square inch and produce a total of about 35 megawatts. The station includes another nine turbines working at a pressure of only 50. pounds. These produce 155 megawatts.

Mr A. C. L. Fooks, the project engineer, said nearly all the turbines would eventually have t.o work at similar low pressures. The high-pressure machines would have to be replaced or their production lost. He des'cribed the loss in pressure at the bores as perfectly natural and said it had been expected.

"Bores only have a certain life," he said. "As time goes by, their pressure must drop." . Eventually Wairakei would become almost solely

Dased low-pressure duction. At were and 23 with intermediary or low pressures. "Already," he said, "We are finding that we have a shortage of high-pressure holes to keep up that supply) and a surplus of low-pres-sure ones." Hole after hole had been abandoned for high-pres-sure production and four - or five new ones drilled each year to keep up the supply. "But," he said, "This can't go on. The holes we abandon are perfectly good for many years of low-pressure production." Generally, the fall in pressures was far below the surface. At a depth of 2000 ft. pressures had dropped from 700 pounds 13 years ago to about 500 pourids today. Closer to the surface t'he decrease was far less until at the actual bore head the pressures was generally Jittle charged from the original 250 pounds.