COIN Soap Box Meeting #5 (SBM#5)
Downhole Control Line Wet Connectors:
Hydraulic, Electric And Fibre Optic Connectors….
Are They Reliable Completion Options Today?
June 1, 2011
Topic:
Permanent downhole pressure & temperature gages
(DHPG) and related wet and dry mate connectors
• Experience from 60 deepwater subsea wells in GOM spanning
10 year period
• High failure rates were experienced initially, 40% failure rate
within 6 months, 60% within 2 years, but some within weeks
• Extensive RCFA study conducted between Operator, Tree
vendor and DHPG vendor
• After RCFA study and design/process improvements, achieved
near 100% survival reliability
We put you first.
And keep you ahead.
96
84
72
60
48
36
24
12
6
3
operational time [months]
120%
reliability [%]
100%
80%
60%
40%
20%
0%
GEN-1 '93-'96
GEN-2 '96-'99
GEN-3 '99-'01
GEN-4 '01-Sept '04
GEN-5 '03-Sept '04
GEN-2 '96-'99 incl DVA
We put you first.
And keep you ahead.
Economic Importance of Functional DHPGs:
• Downhole pressure & temperature gauges installed to collect
valuable reservoir data
• Permanent DHPG serve as "eyes and ears" for the production
engineer to assess well performance
• DHPGs are expensive, but data particularly valuable during
initial production
• NPV of project can be improved by $MM with working DHPGs
We put you first.
And keep you ahead.
Background Information on Failures:
• High frequency of DHPG failures, some lasted only a few weeks
• Diagnostic tests suggested a short circuit near the subsea tree /
tubing hanger location (indicated via TDR tests)
• Damaged insulation on wiring suspected (nicks seen on electrical
pass-through wiring damaged during assembly operations)
• Leakage of seawater into system, or condensation within passthrough bores, also suspected as potential cause of delayed failures
• Unable to definitively diagnose problems in-situ (inaccessible)
• Formal Root Cause Failure Analysis project conducted to evaluate
most probable failure modes and root causes
We put you first.
And keep you ahead.
The DHPG is a
complete “system”.
This is not a commodity item,
but is an engineered product
requiring the same rigor that we
do for all our subsea kit.
Key to success was the full
integration with all vendors and
engineers/stakeholders/contributor
s from design thru execution and
start up
We put you first.
And keep you ahead.
Potential Root Causes Identified:
• Seawater ingress between male/female interface of wet mate
coupling (misalignment or damage during installation)
• Damaged insulation on wire passing through tubing hanger
(damaged at assembly or later from vibration)
• Damage to or contamination of rubber boot over soldered
connection on dry mate (plus condensation in TH pass-through bore)
• Damage to seals between dry mate and downhole electrical cable
(TEC tubing) allows seawater ingress
• Degradation of elastomer seals due to solvents and or well chemicals
We put you first.
And keep you ahead.
Tubing Hanger Electrical Feed-through:
•
Tubing hanger manufactured by tree vendor, electrical connectors and
penetrators provided and installed by separate vendor
•
Original DH circuit passed through tubing hanger via small loose wire
between wet mate (on top) and dry mate (on bottom)
•
Thin insulation on electrical wire easily damage when installing past threads
in tubing hanger bore
•
Extra length of wire required for access to solder dry mate to wire when
installing through tubing hanger
•
Difficult installation procedure working on large tubing hanger at wellhead
shop
•
Pushing extra wire back into threaded hole in tubing hanger proved to be a
trickey operation
•
“Bunched up” wire pressing against rough bored surface could cause
delayed damage to insulation and short circuit
•
Multiple nicks on wire insulation observed during course of projects
We put you first.
And keep you ahead.
Tubing Hanger Electrical Feed-through (Cont’d):
• Difficult soldering operation to connect pass-through wire to dry
mate on bottom of tubing hanger
• Rubber insulating boot over soldered joint may not seal if surfaces
contaminated during soldering operation
• Discovered solvents used to clean up soldering flux might damage
rubber insulating boot and/or act as conductor
• Condensation within cavity in tubing hanger could cause delayed
failure if rubber boot on solder joint is not sealing properly
• Protective shipping cap sometimes left off dry mate connector below
tubing hanger, allows contamination of "clean" internal surfaces
We put you first.
And keep you ahead.
Tubing Hanger Feed-Through Improvements:
• Redesigned tubing hanger to eliminate 2-piece electrical
penetrator
• Replaced with integral mandrel penetrator unit that is
easier to assemble (can build on work bench rather than
in high bay)
• Mandrel penetrator integrates wet mate male connector
on top and dry mate connector on bottom
• Penetrator seals into tubing hanger with static seals
We put you first.
And keep you ahead.
Field Connection of Downhole Cable to Dry Mate
below Tubing Hanger:
•
Slow leakage of seawater into dry mate connector via cable connection
could explain delayed failure
•
Difficult procedure for attaching downhole cable to dry mate on bottom of tubing
hanger
•
TEC (tubing encapsulated metal) downhole cable is stiff and hard to manipulate
when making up to tubing hanger
•
Manual process to cut off excess metal tubing on TEC without damaging electrical
wire within
•
Striping off plastic covering on TEC is also manual process (pocket knife)
•
Any nicks or flattening of metal tubing on DH cable could interfere with seawater
seals in dry mate connector
•
Limited working space, difficult access, connection made on rig floor (wet, dirty
environment)
•
Installation is typically on rig’s critical path, pressure to finish connection ASAP
We put you first.
And keep you ahead.
Field Connection of Downhole Cable to Dry Mate
below Tubing Hanger (Cont’d):
• Test port on dry mate connector intended to verify function of
seawater seals (connector relies on multiple one-atmosphere seals)
• Discovered problem with dry mate test port design: Shoulder on
parts could form unintentional seal and prevent the test pressure
from reaching the critical seals
• Damaged metal tubing or seawater seals would thus not be
detected by the pressure test
• Ferrule type seals used to exclude seawater are actUally working in
reverse direction from normal application
• Sealing of the ferrule fitting in this application is highly dependent
upon surface condition of TEC tubing (exposed to damage during
cutting and stripping)
We put you first.
And keep you ahead.
Wet Mate Alignment and Make Up:
•
Wet mate female mounted on long flexible extension ("quill") below tree
•
Wet mate male connector rigidly mounted in top of tubing hanger
•
Flexibility of quill compensates for machining tolerances & clearances
•
Some “bent” quills discovered that pushed wet mate female off center
•
Entry bevel on wet mate female was very small (only accommodated about
1/16" offset)
•
Centralizing bushing for wet mate allowed "float" but was not spring
centered
•
Bent quills could move wet mate female far enough off center to "crash"
when landing on male connector
•
Corrected the problem by rigorous inspection to detect bent quills at
assembly stage
•
Consider larger entry bevel or spring loaded centralization mechanism for
future improvements
We put you first.
And keep you ahead.
Results:
• Improved designs for electrical pass-through systems on tree
and tubing hanger greatly reduced chance of damage during
assembly
• Improved design of dry mate connector and field installation
procedures ensures proper make up of critical seals
• Increased attention to detail at all phases
• Eliminated initial failures and short term delayed failures
• DHPG reliability now running above 95%
We put you first.
And keep you ahead.
We put you first.
And keep you ahead.
We put you first.
And keep you ahead.