| Title | ROTORUA GEOTHERMAL FIELD – EXPLORING METHODS TO MEASURE HEAT AND FLUID USE |
|---|---|
| Authors | J. Barber, P. Doorman, J. Laurent, and A. Austin |
| Year | 2017 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Rotorua, geothermal, mass flow, temperature, pressure, direct use |
| Abstract | The Rotorua Geothermal Field is unique in that is one of the few high temperature systems in New Zealand that is predominantly tapped for individuals direct use, rather than for large scale energy generation. The wells are shallow, typically less than 150m depth (with most about 80 – 120m deep), for small scale use (typically 50 to 200 tonnes/day), and temperatures range from 90°C to 200°C. To manage geothermal resource allocation, a model was developed in 1994 by Bay of Plenty Regional Council (BOPRC) resulting in a policy limiting discharge to waste to protect surface features. All other abstraction required to be reinjected back to source. The management policy is to be reviewed and the model updated to corroborate allocation limits. Information needed includes temperature, pressure and flow of the resource from consented wells (wells with the right to abstract fluid/steam). As such BOPRC has developed a pilot flow testing programme to determine the current actual (rather than consented) use of geothermal fluid and energy from the Rotorua Geothermal Field. The flow testing programme has evolved through a range of field trials, seeking to overcome issues that many Rotorua wells exhibit, such as slug two phase flow, scaling, condition of welhead and casings and urban setting; difficult access, enclosed areas, and the ability to dispose of excess test fluid safely. Advancing a method that is relatively accurate, affordable, robust and that is easily transferable across multiple wells with different characteristics has been critical. The trials undertaken have led to the development and refinement of a method that includes fitting a separator loop with inline meter near the reinjection well. Trials have also assessed the effectiveness of various meters, data retrieval methods and the duration of flow testing to optimise data retrieval. |