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SCSSSV API test – Audit
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SCSSSV gas test. Draft 1, issued 15 May 2010. AUDIT version.
This Worksheet calculates the average flow rate of gas through a valve into a closed space during a pressure test, in SCF/min or m3/min. The procedure is defined in API RP14B and to summarise is;
1. Apply the required test pressure below the valve.
2. Bleed off above the valve and record the starting pressure.
3. Record the pressure buildup after 60 minutes (or optionally use a different time interval).
4. Look up the gas deviation factor at 1 bara (14.7 psia) and at the final pressure.
5. Record the temperature at the valve.
6. Note the volume above the valve (into which the gas flowing across the valve entered).
1 |
Initial test gauge pressure, P_test1
psiPakPaMPaBar |
8 |
(The worksheet will convert this to absolute pressure)
Final test gauge pressure, P_test2
60 |
Test duration, minutes, t_test
3.5 |
lm3bblft3 |
Volume above the SCSSSV, v_test
10 |
FCK |
Temperature at the SCSSSV, T_test
1 |
Gas deviation factor at 1 bar, CZs
If the gas deviation factors are not known, use 1 for each. This then assumes a perfect or ideal gas.
1 |
Final gas deviation factor, CZ_test
Click here when any values are modified to update the result.
Calculations
All entered values are converted to SI units within Mathcad and the calculations are done using SI units. The results are displayed in both SI and oilfield units.
Absolute pressure increase,
Standard pressure,
Volume above the SCSSSV,
Standard volume,
Absolute temperature of the SCSSSV,
Standard temperature,
Use the standard combined gas law formula with gas deviation factor to calculate the volume of gas in the cavity at standard conditions. Compare this to the volume of gas present at the end of the test then divide by the test time to get the average volume flow per minute.
This equation calculates the quantity of gas in the test cavity if it is at standard temperature and pressure and accounting for the gas deviation factor at 1 bar (if used).
This equation calculates the quantity of gas in the test cavity at the end of the test and accounting for the gas deviation factor at the final pressure (if used).
This equation calculates the increase in the quantity of gas in the test cavity and divides this by the time taken for the test.
Results
Average flow across valve during the test, equivalent Standard Volumes per minute.
NOTE – the API maximum flow rate to pass the test is 0.425 m3/min (25.485 m3/hour) or 15 ft3/min (900 ft3/hour).
References
1. API Recommended Practice 14B “Design, Installation, Repair and Operation of Subsurface Safety Valve Systems” (incorporates ISO 10417:1993)
2. All of the mathematical variable names are given in accordance with the Drillers.com Standard Variable Naming Convention.
