www.ptc.as

www.ptc.as

New Solutions

for

Annulus Pressure Management

to

Avoid Premature Failure in ESP Wells

Joe Allan PTC

www.ptc.as

Agenda

• The Challenge

– Impact or Annulus Pressure Management on ESP Run

Life/power cable integrity

• Current Solutions

– Manual/Sub Optimal

• New Solutions

– Description / Performance Simulation / Actual Results

• Conclusions

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ESP Completion

Wellhead

BOV

ESP

Pkr

ESP

Cable

Hanger

Annulus

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Annulus Pressure Management: Challenges

• Following well start up

– Well temperature increases

– A Annulus pressure increases

• Annulus Pressure, if not managed carefully can:

– Collapse tubing or burst casing

– Explosively Decompress Power Cable insulation

• 50 psi/min maximum bleed off rate

• Reduce by 50% then hold for 30 min

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Annulus Pressure Management:

Existing Approach

• Subsea wells

– Utilises subsea tree x over valves

• Requires monitoring-human factor

• Difficult to control bleed off rate

• Platform / Land Wells

– Utilises annulus line gate valve

• Requires monitoring-human factor

• Difficult to control bleed off rate

• Remote location

• Might this be a factor in ESP power cable failures?

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Annulus Pressure Management

in Practice

0.06 bbl(2.5 gal)~50 psi

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Annulus Pressure Management (Subsea Wells)

An Automatic, Controlled Solution • Bleed Off Valve(BOV)

• Reconfiguration of existing field proven technology

• Automatic pressure relief valve with bleed off rate control

– Bleeds from “A” Annulus > Tubing

– Preferably installed just below tubing hanger

– Set to open/close at pre-set annulus pressure (P*ann)

– Bleed off rate controlled to protect ESP cable

• Also incorporates

– Well barrier accredited check valve

• Prohibits tubing > annulus flow

• Closes once Pann<= P*ann

• Metal / metal seal

– IPO stem/seat provides backup check valve

– Annulus debris protection

• BOV set shallow with inlet lowermost(gravity separation)

• Shearable filter allowing by-pass in event of blockage

– Shear module to facilitate annulus PT

• tested to +/- 5 %

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Annulus Pressure Management (Subsea Wells)

An Automatic, Controllable Solution

• Technology heritage

– Shear open device with reference chamber

– Labyrinth restrictors

– IPO gas lift valve

• Well barrier check valve assures well integrity

• IPO stem provides secondary barrier

• Bellows controls opening and closing pressures

– Shearable filter

• Dimensions – 9.3” OD (10.75” csg, but can reduce for smaller csg sizes)

– 2 power cable slots

– 2 CL slots

– 5.5” VAM connections

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Well Completion and Production Phases

• Two distinct modes of operation:

– Completion phase(constant temperature):

• Annulus PT required to confirm completion integrity

– Tool initially pinned closed

– Tool sheared immediately after annulus test

– Production phase(increasing temperature):

• When well is put on production, Pann will increase as

consequence of T increase

• The BOV will control rate of pressure bleed-off during

both phases

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BOV Simulator

• Used during product development

– Integrate mechanical design with fluid mechanics

– Type and location of restrictors

– IPO specs

• Used during completion design phase

– Determine specification

• To ensure bleed off rate is < 50 psi/ min

• Unsteady state in time/location

• Models production phase from startup to stabilised

production

– Temperature Increase

– Associated Annulus Pressure increase

– Flow processes through the BOV

• Models initial shear during completion phase

𝑑𝑉

𝑑𝑡=𝜕𝑉

𝜕𝑇∗𝑑𝑇

𝑑𝑡+𝜕𝑉

𝜕𝑃∗𝑑𝑃

𝑑𝑡

𝑑𝑉

𝑉= 𝐶𝑇 ∗ 𝑑𝑇

𝑑𝑉

𝑉= 𝐶𝑃 ∗ 𝑑𝑃

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Simulator-Product Development

Mechanical

Design

BOV Simulator Manufacture

Determine BOV specification

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Simulator Verification

• Test well used to check BOV operation

– Temperature effect mimicked by injecting fluid into annulus

• Simulator used to design test/BOV setup

• Initial problems re location of shear sub resolved

• Tool sheared at correct pressure

• Bleedoff rate as expected

• Held pressure as expected

• The tool successfully catered for both the initial shear

and post shear periods

• Actual and simulated performance demonstrated good

correspondence

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Simulation Example

• Vann=100 m3(630 bbl)

• dP/dt< 50 psi/min

• Total fluid bled off~1.2 m3(7.3 bbl)

• 5 off 225 LOHM resistors required

• Pdome~38 bar

• Shear setting 250 bar

-300

-200

-100

0

100

200

300

0

50

100

150

200

250

300

0 5000 10000 15000 20000

dP

/dt(

psi/m

in)

Pan

n(b

ar)

, Tan

n(°

C),

Q(m

3/d

)

Time (sec)

Example Well - Annulus Pressure Bleed-off

Q

Pann

Tann

dP/dt

dP/dt=50 psi/min

Initial shear pressure

Annulus temperatureincrease due to ESP start-up

Annulus pressure increase due to ESP start-up

ESP start-up

Auto bleed-off at 38 bar

Completion Phase Production Phase

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Annulus Pressure Management (Dry Tree Wells)

An Automatic and More Controllable Solution

• Existing Scenario:

– Bleeding off through manual gate valve

• Enhanced Scenario:

– Surface Annulus Safety Valve (M SAS)

• Check valve buried in VR profile

• Hydraulic Actuated to open

– Local hand pump or

– Remote control hydraulics

– In response to P Ann> MAASP

• Choke in actuator flow tube

– Sized to control bleed off rate

• Can install actuator in modified gatevalve(MSAS G)

– Eliminates surface pipework mods

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Conclusions

• ESP Lifted Well Annulus Pressure Management Guidelines – Max Bleed off rate < 50 psi/ min

– Very difficult to achieve with existing technology

• Sub Sea Xmas tree x-over valves

• Dry tree annulus line valves

– May be a factor in premature ESP failures

• Explosive decompression of power cable insulation?

– Solutions to automate and control the process been developed

• Reconfiguration of existing field proven technology

– Simulator developed to model the tool performance

• Good history match achieved with test data

www.ptc.as

PTC Standard Sales Conditions

GENERAL LIABILITY

In lieu of any warranty conditions or liability implied by law, the Seller’s

liability in respect of any defect in or failure of the goods supplied or from any

loss, injury or damage attributable thereto is limited to making good by

replacement or repair defects which under proper use appear therein and arise

wholly from faulty design, material or workmanship within a period of 12

months after the goods have been dispatched providing always that the such

defective goods are promptly returned free to the Seller’s works unless

otherwise arranged. The repaired or new parts will be supplied ex works by the

Seller.

In the case of goods not manufactured by the Seller the Buyer is entitled only

to such benefits as the Seller may receive under any guarantee to the Seller in

respect thereof.

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Test Results (Test2-I/R/S)

• Put shear sub at bottom to protect IPO

• Sheared OK

• Pann decreased to ~1300 psi and held (pumping small pmp throughout)

• Test successful

29/11/12-Test2(I/R/S)

0

500

1000

1500

2000

2500

3000

3500

4000

29/11/2012 12:00 29/11/2012 14:00 29/11/2012 16:00 29/11/2012 18:00 29/11/2012 20:00

Time

P(p

sig

)

Ptbg_corr AKER-PSI

Pann_corr AKER-PSI

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Test Results (Test4-R/S)

• Redressed shear sub and rerun(R/S)

• Sheared OK

• Pumping at max rate of 12 l/min(109 b/d) to test restrictor

• Good correspondence theory vs actual

30/11/12-Test4(R/S)

0

500

1000

1500

2000

2500

3000

3500

4000

30/11/2012 12:00 30/11/2012 14:00 30/11/2012 16:00 30/11/2012 18:00

Time

P(p

sig

)

Ptbg_corr AKER-PSI

Pann_corr AKER-PSI

Test

0

500

1000

1500

2000

2500

3000

3500

4000

30/11/2012 09:36

Time

P(p

sig

)

Ptbg_corr AKER-PSI

Pann_corr AKER-PSI

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Matching Restrictor Performance

• Setup : R/S

• Krest=20.8 via matching(cf catalogue value of 20)

30/11/12-Test4(R/S)

0

100

200

300

400

500

600

700

800

900

1000

30/11/2012 16:48 30/11/2012 17:06 30/11/2012 17:24

Time

PR

ES

S(p

sig

)

0

5

10

15

20

25

30

35

40

Kre

st,

DP

Ptbg_corr AKER-PSIG

Pann_corr AKER-PSIG

DP(psi)

Krest

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Vary Ptbg