Economic optimisation of the Ohaaki Geothermal Field dual-flash system indicated the requirement to program for sliding High Pressure turbine inlet pressures and the de-rating of individual wells to Intermediate Pressure. A wellbore simulator was used to generate output curves up to 5 years into the future to enable 'what-if modelling for maximum electrical generation under different scenarios. The key to predicting future output curves as a function of wellhead pressure was predicting two-phase well productivities as a function of field pressure and enthalpy trends. Using a wellbore simulator to generate inflow pressure curves from output test data and matching measured downhole data showed that the Duns and Ros flow correlation produced a linear response with a consistent relationship to static pressures for most wells. 'This was used to generate predicted output characteristic curves up to 1998, enabling the modelling of varying turbine inlet pressures.

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Copyright 1994, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.