Seal 9 barrier verification by xLOT and

Communication testP&A Forum 18th Oktober 2017

Daniel Tomczak and Roar Flatebø

2

Valhall overview and P&A Strategy

Qualifying External Barriers

Coil Tubing Operation

Regulations

Leak Off and Communication test

Field example, result

Discussion

Conclusion

Content

3

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

4

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)

14

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

15

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