Geothermal heat flow at Wairakei during 1958

Evolution of the Wairakei geothermal reservoir during 50 years of production

“…1). The natural heat and mass discharge from Wairakei has been assessed by several authors with average values around 400 kg/s and 400 MWt (Fisher, 1964;Allis, 1981;Hunt et al, 2009).…”

Geothermal reservoir simulation: 3. Application of liquid‐ and vapor‐dominated hydrothermal modeling techniques to Wairakei, New Zealand

“…In general, recharge occurred toward the west where the Wairakei hills are located, and discharge occurred toward the east. The accepted total natural mass flow rate for Wairakei as computed by Fisher [1964] is 440 kg/s. The total discharge rate computed in this modeling work is 424 kg/s, with most of it occurring in the production area.…”

“…Although some mass discharge was measured, the total initial natural mass discharge was not; however, it can be estimated from the measured heat flow. Fisher [1964], using a mean enthalpy of 1.025 X 108 J/kg and omitting the heat flow due to conduction, obtained a mass discharge of 440 kg/s for the 1951-1952 period. Fisher also noted that the natural heat discharge between 1951 and 1958 appears to have remained relatively uniform, whereas the natural mass discharge decreased, resulting in more steam and less water being discharged.…”

“…The natural heat flow at Wairakei has been measured several times, beginning in 1951. Fisher [1964] gives a summary of results obtained by various authors during the period 1951-1959. The values range from 3.431 X 108 to 6.820 X 10 • J/s; however, Fisher concludes that the best value for natural (preexploitation) heat flow at Wairakei is approximately 4.184 X 10 • J/s, where a heat flow reference temperature of 12øC is used.…”

“…It is interesting to note from the plot of leakage through the Huka Falls Formation, that the natural discharge at the surface should decrease with time, and by approximately 1964, the total natural discharge should be 'captured.' As noted by Fisher [1964], the observed natural mass discharge did de- I I I I I I I I I I I I I I I I I I I I I I I I I end of the history match. The hydraulic properties providing this amount of leakage were required to be large in order to maintain production during the peak discharge years of 1962-1964.…”