Seal 9 barrier verification by xLOT and Communication test
Transcript of Seal 9 barrier verification by xLOT and Communication test
Seal 9 barrier verification by xLOT and
Communication testP&A Forum 18th Oktober 2017
Daniel Tomczak and Roar Flatebø
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Valhall overview and P&A Strategy
Qualifying External Barriers
Coil Tubing Operation
Regulations
Leak Off and Communication test
Field example, result
Discussion
Conclusion
Content
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Valhall DP P&A strategy:
• Establish barriers as deep as possible.
Efficiency in P&A is contingent on simplifying operations
based on learning from repeated operations
• Establish a track record, then apply to analogous
wells/scenarios.
Continuous Learning and Risk Reduction
Valhall DP P&A Strategy
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No logging tools available
Rig operations complex and time consuming
• Pull tubing and packer
• Mill out inner liner (5,5” 45,5 ppf heavy wall)
• Log
• Potentially perf and wash (tool size)
• Potentially mill second liner.
• Cement and test
Dual Cemented Liner
Qualifying External Barriers
Seal Assembly at 3045mMD, 2359mTVD
7" Liner shoe at 3172mMD, 2483mTVD
7" ECP at 3152mMD (not inflated)
Muleshoe 3050 mMD
7" ECP at 3162mMD (not inflated)
Gauge Carrier at 3035mMD, 2349mTVD
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What can we do with existing intervention tools?
We can perforate
We can set plugs
We can isolate perforations
We can pump cement
Dual Cemented Liner
Qualifying External Barriers
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Isolate reservoir with permanent bridge plug.
Perforate dual cemented liners in to Seal 9
Perform xLOT to verify external-most barrier to reservoir
Perform communication tests in xLOT between 30 m perforations up and down
(3 sets minimum)
• Confirms liner annulus cement
• Confirms external-most barrier
Lay cement across perforated interval and pressure test
Communication Testing in xLOT mode
CT Seal 9 Coiled Tubing P&A Strategy
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Perforated 16 zones: success every time.
Perforated two zones in one run.
Perforated casings:
• A-2, 3 zones: 5” 23,2 ppf x 7” 29 ppf cemented (0,89” of steel)
• A-19, 6 zones: 5-1/2” 45,5 ppf x 7-5/8” 33,7 ppf cemented (1,36” of steel)
• A-12, 7 zones: 5-1/2” 45,7 ppf x 7” 32 ppf cemented ((1,39” of steel)
Repeatable xLOT in every perforation at expected values.
CT Perforating Multiple Casings
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Tested numerous CT packer tools
Used Retrievable bridge plugs with memory pressure sensors under
Optimized tool selection based on tool mechanics and well status (i.e. well deformations).
3 wells with access to Seal 9
External formation integrity/cement integrity confirmed in every well.
Repeatable xLOT in every perforation at expected values.
• Attempted drawdown test to induce shale influx
Good liner annulus cement was found in three diverse well configurations and cement ‘qualities’
Developed new strategy and tool selection process to reduce risk, scope and time for further campaigns.
Communication Testing
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Conclusions:
• External formation integrity/cement
integrity confirmed in every well.
• Repeatable xLOT in every
perforation at expected values.
• Good liner annulus cement was
found in three diverse well
configurations and cement
‘qualities’
Liner Cement and External Barrier Qualification Matrix
A-2 A-19 A-12
Inner liner size 5" 23,2 ppf 5,5" 45,5 ppf 5,5" 45,5 ppf
Outer Liner Size 7" 29 ppf 7-5/8" 33,7 ppf 7" 32 ppf
liner ECPs yes - not inflated. no no
Centralisation Partial none none
Hole angle at shoe 8,1 deg 90,2 deg 93 deg
Rotation of Pipe yes no - stuck liner yes
Losses <20% 30 % 0
Top squeeze no yes no
Expected annular cement GOOD BAD GOOD
Length between
Lowermost and
uppermost perforation60 mMD 217 mMD 289 mMD
Bottom XLOT
-Leak off and
Breakdown pressures
are corresponding to
expected formation
strength
-The xLOT show expected values regarding
formation strength at the perforated depth
-It is concluded that there are sealing
material outside the casing and no hydraulic
communication to the reservoir or
permeable formations in the overburden
from this perforation
-All breakdown pressures correspond to
expected formation strength.
-Leak off pressures in lower 5 zones
indicated slight permeability.
-Upper 2 perforations leak off to expected
pressure (good liner cement)
Communication Tests
3 perf intervals, all ok. Zone 1 and 2- failed comms test.
Zone 2 and 3 - no communication.
Zone 3 and 4 - failed comms test.
Zone 4 an 5 - no communication.
Zone 5 and 6 - failed comms test.
Zone 1 and 2- failed comms test.
Zone 2 and 3 - failed comms test.
Zone 3 and 4 - failed comms test.
Zone 4 an 5 - failed comms test.
Zone 5 and 6 - no communication.
Zone 6 and 7 - no communication.
Liner Annulus Cement
XLOT And Communication Tests Summary
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Shale as an Annular Barrier: What the regulations and guidelines say
BP
BP
BP
NORSOK
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Shale as an Annular Barrier: What the regulations and guidelines say
Two casing strings exclude logging of potential
shale barrier on the outer casing
Formation integrity (LOT) and communication tests
are performed to qualify log responds
Justification to only use LOT and communication
test
• Perform extended LOT
• Testing with water
• Test sufficiently short intervals
• The test involve both the internal cement
between the casings and the shale collapse on
the outer casing
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Extended Leak Off Test and Communication Test
Perforation at 4066
Perforation at 4096
TOC 4113mMD
Plug with gauge below
Ap
plie
d p
ress
ure
Overview of the entire Extended Leak Off Test cycleOverview of the downhole configuration for
the Communication test
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xLOT and coms test between 4096 and 4066 mMD
Peak pressures ~240-260 bar
Fall off pressures ~213 bar, expected closure pressure
Surf
ace
pre
ssure
(bar)
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Gauge pressure below packerBHP pressure
xLOT and coms test between 4096 and 4066 mMD
Formation breakdown
Fracture closure pressure
Fracture propagation pressure
First cycle, sudden pressure increase when differential pressure is applied, followed by sudden flat platau
Second cycle, sudden increase followed by dropping pressure
The respond on the pressure gauge is interpreted as packer movement and not hydraulic communication due to leak
BH
P p
si
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Overview of perforations and barrier placment and in Seal 9
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Logs give contact length and variation in contact (length and circumferential)
• LOT and communication tests performed to remove uncertainty in the sealing capacity of the bonding
• Uncertainty removed if LOT test performed in an interval with weakest bond, sometime difficult to do as it may require
testing very short intervals
In the absence of logs
• Uncertainty regarding contact length and variation of the bond
• Are LOT and Communications tests of 30 m MD sufficient to qualify an interval ?
• Fluids requirement, water, brine, mud ??
Permeability responds
• Dependent on fluids
• Even ordinary LOT performed with mud show presence of permeability, how to determine acceptable levels?
Length of the barrier is about adding in a safety margin and choke effect when breached?
A barrier in the order of a few meters would be sufficient as long as it is tested and is holding formation strength
(repeatedly) and positioned at relevant depths? However, when breached the choke effect is determined by length
Discussion
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By doing the Extended Leak Off Tests and Communication Tests the consensus in the P&A team is that the method is
sufficient to demonstrate hydraulic sealing intervals
• Tests are performed with water
• Formation Integrity is demonstrated according to expected values
• Tested intervals is believed to be sufficiently short
• By adding up the tested intervals barriers are according to regulations
Conclusion