FREQUENTLY ASKED QUESTIONS

The Phase Dynamics Water Cut Analyzer provides two means by which to enter and determine the salinity of the produced water.

1.) Use of the Refractometer

The first is through the use of a salinity refractometer. This is a hand held optical instrument which uses the principal of the greater the salinity, the greater the refraction of the room light entering the prism area of the instrument. The user obtains a clean sample of the well's produced water (oil in the water will cause the line to be fuzzy), zero the refractometer, and then determine the salinity of the produced water.
a.) The refractometer is zeroed by placing distilled water on the prism area and using the adjustment screw on the top to set the blue line on zero.
b.) The produced water should be allowed to cool to the same temperature as the distilled water used for the calibration.
This corrects for temperature effects. The scale on the left gives a direct readout of percent salinity (0-10% or 0-5%) while the right hand scale is the density in grams/cc. This salinity value in percent can be directly entered into the Phase Dynamics menu for salinity. This is done when a water continuous emulsion does not exist in the well stream and a nearly correct value is required for the future time when the well will go water continuous.

2.) Salinity Calibration Mode of the Phase Dynamics

The preferred method to determine and enter salinity is through the "Salinity Calibration" which is in the Phase Dynamics' Menu. A "Standard Salinity Calibration" allows the calculation of the salinity by knowledge of the water cut of the well. The refractometer measurement of salinity is used to compare the values obtained from the "Standard" salt calibration to check both the instrument's operation and the validity of the sample you will pull during the calibration. Provision for the pressing of the "Enter" push button is made while a sample is being pulled from the stream. This push button is again pressed when the sample is complete. Once the sample has been analyzed for water cut through distillation or centrifuge, the resultant water cut is entered into the Phase Dynamics unit. This allows the Phase Dynamics system to then calculate the salinity from the frequency and temperature obtained during the sample pull. The water cut entered by the operator then completes the required information to calculate the apparent salinity.
The "Detailed Salinity Calibration" is the same except that the refractometer's reading is input and is then used to calculate a frequency offset which would bring the same salinity as the refractometer into use. Please use the "Standard" calibration unless otherwise requested by the factory.

Solutions for Salinity Measurement Problems

1.) Refractometer Solutions

If you have problems obtaining a clean water sample please order the following items from the Cole Palmer Chemical Company. Watman 13mm ZC Syringe Filter, Cat. #6858-1327 pkg. Of 200 (approximate cost is US$1.00 each filter). The filter part number is not in the catalog but, it is a standard stocked item. The filters are small round items which connect directly to the end of the syringes. Use two filters in series if the water is very dirty and one filter cannot eliminate the oil film. Since the filter cost is very low, please discard after use to prevent contamination of new samples from the possibly higher salts from the previous sample.
The refractometer is a validity check on the operation of the system and the sample integrity. If the two methods vary, it is typically due to the sample's integrity.

2.) Phase Dynamics' Salinity Calibration Solutions and Guidelines

If the calculated salt from the "Standard" salinity calibration is greater than +\-20% of the refractometer's reading (i.e. you read 1.5% salt on the refractometer and the "Standard" salt cal gives you a salt of 1.0%, this is greater than -20% of 1.5%) there was a problem with the sample, its analysis or your salt make up. In this case the produced water may contain very little NaCl and instead may contain larger concentrations of less conductive salts such as Ca2Cl3.

3.) Obtaining a Valid Sample

Typically, the manner in which the sample was obtained is the source of the greatest error at the higher water cuts.

a.) The upstream sample port should be after a mixer or have many elbows with high flow rates to assure mixing.
b.) A pitot or quill should be installed in the sample port to obtain a sample out of the center of the flow.

Samples obtained from the sides or bottom of the pipe may be biased either way depending upon flow and oil conditions. When in doubt the best approach is to enter a salinity of approximately 10% less than the refractometer's reading.
If the sample port is located some distance in front or in back of the Phase Dynamics Measurement Section a biased sample may be obtained for two reasons: 1.) the operator cannot read the Phase Dynamics Display during the sampling to assure a constant water cut reading 2.) the process may be dynamic and due to flow conditions the sample time frame was too short to encompass the changes in water cut. This would lead to another problem where the water cut is changing rapidly and therefore an average sample would be difficult to obtain.

3.) Use the Separator to Obtain a Water Only Dump:

The Phase Dynamics' system continually displays the instantaneous water cut at the previous entered salinity during the sample time frame. This should be within the operator's line of sight while the sample is pulled to observe the change in water vs time. The best opportunity to obtain a valid sample is to raise the two phase separator's fluid level to get a water dump which will last for 30-60 seconds. Then a sample can be easily obtained and validated that it was 100% water during the "Enter to Start" and "Enter to End" sample time frame.