| Title | Modelling Geothermal Surface Features in the Rotorua Geothermal Field |
|---|---|
| Authors | T.M.P. Ratouis, M.J. O’Sullivan, J.P. O’Sullivan |
| Year | 2016 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Geothermal modelling, Rotorua geothermal field, geothermal surface features, Wells on deliverability |
| Abstract | The Rotorua Geothermal Field is a shallow high enthalpy geothermal reservoir lying directly beneath the Rotorua city in New Zealand. It is renowned for an abundance of natural geothermal manifestations including the geysers and hot springs at Whakarewarewa. However surface geothermal activity waned in the 1970s and a decline in surface discharge of geothermal manifestations in response to excessive withdrawal of geothermal fluid was observed. A monitoring programme was instigated in 1982 followed by the introduction of a wellbore closure programme in 1986 which resulted in recovery of some surface features. As part of the Resource Management Act, forty-one of the most significant features have been monitored from May 2008. These records provide valuable insights on the state of the reservoir and health of the surface features in particular for field management purposes. A full-scale three dimensional numerical model of the Rotorua geothermal system has been built to replicate the past and current behaviour of the geothermal field and surface features. Correlation factors between the model outputs for the first ten layers (temperature and pressure) and temperatures recorded from May 2008 to September 2014 were calculated to determine a likely feed depth of the surface features at Rotorua. These were then used to implement wells on deliverability at the required depth. This is to explore various ways to represents surface features in a geothermal field. The aim is to complement and to help interpret the Rotorua monitoring programme data by providing a tool which can identify and replicate spatial and temporal trends of the surface features at Rotorua of natural and anthropogenic origins. |