The Geothermal Two-Phase Orifice

Abstract

Real time measurement of the mass flow rate and enthalpy of two-phase wells is important for the management of geothermal development and monitoring individual well outputs. Existing techniques for measuring the output of two-phase wells are either expensive (separators), low in accuracy (tracer dilution) or require the geothermal well to be taken out of production (horizontal discharge) for testing. Several new real-time two-phase flow measurement methods are being investigated using both laboratory and field-testing. The two-phase orifice plate is the most widely examined method and has also been implemented in several geothermal fields worldwide. In this work, extensive geothermal field testing in New Zealand and Indonesia were used to examine existing correlations for two-phase flow measurement using the concentric sharp-edge orifice plate. These correlations are relatively complex and include several empirically derived and calibration parameters. A new simple correlation with high accuracy was also presented in this work. Results from a novel new orifice plate design and implementation allowing the real-time acurate mesurement of both mass flow rate and enthalpy at low cost in geothermal pipelines are also presented