| Title | Modelling the Ngawha Geothermal Field |
|---|---|
| Authors | J. Burnell, G. Weir, W. Kissling |
| Year | 2016 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Ngawha, Reservoir Modelling, Expansion, Spring Flows |
| Abstract | The Ngawha Geothermal Field is located in Northland, New Zealand. In 1998 a 10 MWe power station was commissioned on the field and in 2008 a second 15 MWe stage was added. At that time, concerns about the impact of the expansion on the Ngawha Springs resulted in the use of supplemental injection of fresh water to maintain reservoir pressures. In this paper, we will present the development of a numerical reservoir model of the Ngawha Geothermal Field by GNS Science. This model was developed to assess the impact of a proposed expansion of electricity generation of up to a total of 75 MWe on the geothermal field and the environment. The reservoir model was based on the conceptual model that had been developed in the 1980s and updated in 2014 to account for the response of the reservoir to 16 years of production and injection. The reservoir model was formulated as a dual porosity model. Calibration was done using natural state measurements, the response to historical production, tracer tests and interference tests. In order to more accurately assess the impact of the proposed expansion on the Ngawha Springs, a separate model of the connection between the geothermal reservoir and the groundwater system was developed. The details of both models and the predictions of the impact of the proposed expansion will be presented. |