8.3 Adn 8.4 by Opi

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geothermal stage
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  8.3 PRODUCTION TESTING METHOD Selecting the type and size of equipment needed to test a geothermal well depends on the expected production rate, pressures, and the fluid type. The available equipment, the duration, and the accuracy required for the test will also be factors in selecting the test equipment. Where environmental conditions permit, a brief vertical discharge direct to the atmosphere can be used with the lip pressure method to get a first estimate of the longer-term production potential and to determine the most suitable equipment for longer-term testing. During a vertical discharge, the fluid enthalpy can be estimated by observation of the discharge plume, the fluid chemistry, and downhole conditions at the feed zone prior to discharge. The vertical discharge also helps to clear debris from the well. The main methods used for flow-testing geothermal wells: 1.   Single-phase measurements (standard orifice or weir flows for single-phase steam or liquid) 2.   Total-flow calorimeter 3.   Separator 4.   Lip pressure (James) method 5.   Tracer dilution method 8.4 SINGLE-PHASE FLUID 8.4.1. Low Enthalpy Wells Where the temperature of the flowing geothermal fluid can be measured in liquid conditions, the fluid enthalpy can be obtained directly from the steam tables. The enthalpy of the fluid entering the well may be obtained by downhole temperature measurements in liquid conditions below the depth where produced fluid starts to boil. If the downhole temperature of a flowing well is used to obtain the discharge enthalpy, it is assumed that there is no heat loss from the wellbore or that the heat loss is less than the accuracy of the temperature measurement. This information may be available only at smaller flow rates where well pressures are high enough to prevent  boiling. Where no boiling occurs, the mass flow rate can be obtained directly using a standard orifice plate [ISO 5167] or weir [ISO 1438/1] and the enthalpy from the wellhead temperature. Where the fluid enthalpy is great enough to cause boiling, the total mass flow rate can be calculated from the liquid temperature (measured downhole at the feed zone), together with the water flow separated at atmospheric  pressure using the Flash Correction Factor. Example : From downhole temperature and pressure measurements, a geothermal well is known to have a liquid feed temperature of 200 ° C. While the well is flowing, the separated water flow at atmospheric pressure measured after flashing off the steam is 10 kg/s. Atmospheric pressure is 1 bar. What are the discharge enthalpy, the total mass, and the heat flow rates? Procedure: Using the steam tables, at 200 ° C the liquid enthalpy is 852 kJ/ kg, and the mass flow is : 8.4.2. High Enthalpy (Steam) Wells At the other extreme from the low enthalpy “hot water”  wells are those that produce saturated, or superheated, steam. Where the noncondensable gas content of the steam is small (less than   2% by weight) and there is a slight superheat, the flowing enthalpy can be obtained by plotting the pressure-temperature conditions for the steam on the Mollier chart.    Where the steam is slightly “wet,” enthalpy can be measured using a throttling calorimeter to reduce pressure to saturation conditions (ASME PTC).
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