| Title | Origin and Impacts of High Concentrations of Carbon Dioxide in Geothermal Fluids of Western Turkey |
|---|---|
| Authors | Jill R. HAIZLIP, Manon M. STOVER, Sabodh K. GARG, Fusun TUT HAKLIDIR, and Nicholas PRINA |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | enthalpy, flow testing, high non-condensible gas |
| Abstract | There are several different methods for estimated total mass flow and enthalpy during testing of two-phase geothermal wells. Not all methods for flow metering calculations are equally applicable. Geothermal resources with high non-condensable gases (NCG) concentrations may require a different methodology over geothermal resources with low NCG. During typical flow testing of newly drilled two-phase geothermal wells, the liquid phase and vapor phase are discharged through a pipe into a silencer and separated under atmospheric conditions. The mass flow rate of the liquid phase can be measured by flowing the liquid discharge of silencer through a properly designed weir box. The total flow can be estimated by correcting the liquid mass flow rate for steam loss if the total enthalpy is known. In flowing two-phase low-salinity geothermal wells, the enthalpy of the total flow is very close to the enthalpy of liquid water at the temperature below the bubble point or when the flow is still single phase. This temperature can be obtained from dynamic pressure-temperature surveys and the enthalpy from steam tables. This enthalpy can be refined using wellbore simulation to account for changes resulting from fluid flowing up the well. Alternatively, enthalpy and total flow rate can be resolved by applying the James equation to lip pressure measurements at the end of the discharge pipe if the liquid flow rate is known. Calculated total enthalpy from the James Lip Pressure Method applied to flow test data of geothermal wells completed in high ( more than 2% by weight in the reservoir) gas, moderate temperature (170 to 220°C) liquid-dominated geothermal systems has produced results very different from the measured downhole flowing PT surveys. By comparing data sets of enthalpies from James Lip Pressure Method and dynamic PT surveys in wells with various flow rates, enthalpies and total gas concentration, a relationship is derived to improve well test results from these high gas wells. This paper presents the evaluation of the different well flow test methodologies applicable to high NCG geothermal fluids using data from multiple well tests. |