Is it necessary to install a downhole safety valve in a subsea ... - NTNU

Component: DHSV (TRSCSSV flapper type)
Failure rate
(10 -6 /hours)
Reliability data dossier
Failure mode
Data source/comment
5.84 Total Data for TRSCSSV, Reliability of
well completion equipment - Phase
II p.20. Operational time 996.79
2.87 ITL=
LCP: 27.5%
FTC: 21.6%
=49.1%
0.34 EXL=CLW=5.9%
years, failures 51.
Failures regarding leakage through
the DHSV. Reliability of well
completion equipment - Phase II
p.21.
Failures regarding leakage through
the DHSV control line. Reliability
of well completion equipment -
Phase II p.21.
3.00 Total Reliability of surface controlled
Sub Safety Valves- Phase IV p.18.
Operational time 1140.9 years,
failures regarding the SCSSV for
all TRSCSSV, 30.
2.06 Total Reliability of surface controlled
Sub Safety Valves- Phase III p.61.
Operational time 941.6 years,
1.68 LCP: 11.8%
FTC: 52.9%
=64.4%
Recommended values for calculations:
Failure rate (10 -6 /hrs):
EXL: 0.3
LCP, FTC: 2.8
failures 17.
Testing and maintenance:
The DHSV is tested every 6 months and repaired if failure is detected.
Comments and leakage paths:
Reliability of surface controlled
Sub Safety Valves- Phase III p.62.
Operational time 941.6 years,
failures 17.
The leakage is trough the DHSV, leading the fluid up the production tubing. External leakage is
from the DHSV to the annulus.
D-3