Measuring Circumferential Metal Loss

Rates in Subsea Pipelines

Presented by

Dan Clarke

1

Dan Clarke

7 December 2012

Contents

Introduction to Corrosion Monitoring

RPCM™ Technology Overview

2

Measurement Performance

Case Studies

Inspection

Data

Introduction to Corrosion MonitoringIntegrity Management

3

Mitigation

Monitoring Data Analysis

Integrity Monitoring forms an essential part of any Integrity

Management Strategy

Introduction to Corrosion MonitoringCorrosion Modelling

4

?

S R

ProtectedExposed

x S

RPCM™ Technology OverviewElectrical Resistance Measurement Principle

5

Cumulative Corrosion (x0 – x) = f(VS / VR)

Corrosion rate = -dx / dt

VS VR

I

bl

xx0 S

RPCM™ Technology OverviewSubsea Corrosion Probe

6

Basic implementation of high resolution ER measurement.

• Full circumference corrosion and temperature measurement (8 sectors)

• CEION® technology sub-micron measurement

• Welded or flanged into pipe

• Designed for life of field (>25 years)

RPCM™ Technology OverviewKey Attributes

S1S2

S3

S8

S7

S6S5

S4

7

• Designed for life of field (>25 years)

• No diameter transition / ‘piggable’

• Typical applications: flowline spools, export pipelines, onshore

• ‘Online’ device (Modbus, Canbus)

• 18-30VDC continuous, <10W

• Qualified for subsea HTHP applications

• 15kpsi, 350F, 3000m water depth

S5

HPHT(High pressure High Temperature)

PUP PieceCustomer supplied Material

Recoverable Electronics Drop Protection Frame

RPCM™ Technology OverviewComponents

8

Inner spoolForged Reducers

PUP PieceCustomer supplied Material

RPCM™ Technology OverviewRing Pair Sensor Operation

CRA flange

Pipe rings

9

• Ceramic coated rings machined from free-issue pipe (usually carbon steel) are

retained between 2 CRA flanges.

• Sample rings inner surfaces are left uncoated.

• Ceramic provides isolation and corrosion resistance.

• Wires attached on outside of sensor rings are fed out to a non-retrievable pod via

primary and secondary HTHP penetrators.

S RS R S R

Electrical Contact

Sample Reference

IIN,0

I1,IN

12

3

6

7

8

12

3

46

7

8 Sector Metal Loss (nm)

Ref Temp (degC)

1

2

3

Ring Pair Data

I1,OUT

RPCM™ Technology OverviewMeasurement Operation

10

45

6 45

6

• Sample and Reference Rings are in series with one another and a controlled current source.

• Each Ring Pair operates independently from other Ring Pairs (allows redundancy).

• For each measurement cycle, current is injected in Mode 0 (4sec), then switched to Mode 1 (4 sec).

• Total measurement cycle is approximately 10 seconds.• Real time calculation of Metal Loss per sector

3

4

5

6

7

8

Average

IOUT,0

RPCM™ Technology OverviewRing Pair Configurations

Ring Pair Type Corrosion Type

General “Uniform”, TOL, Mesa, Pitting

Welded Preferential Weld

11

• Corrosion mechanisms measured

by changing geometry and ring

material

• 2-4 RPs is the ‘standard’

configuration but more possible.

• Typical Config: 4 RPs, 2 General, 2

Welded

CRA (e.g. Duplex) Pitting

Pre-Pitted Pitting / Crevice

High Sensitivity All

Redundant All

Measurement PerformanceThe Importance of Resolution

Corrosion Rate Time to Detection

1 micron resolution

100 microns resolution

0.1 mm / yr <4 days 1 yr

0.5 mm / yr <18 hours 73 days

12

• Resolution is defined as the smallest change that can be

detected

• High resolution enables changes in corrosion rate to be

identified quickly.

• An amount of metal equivalent to the resolution is lost before

the operator has a chance to respond.

0.5 mm / yr <18 hours 73 days

1.0 mm / yr <9 hours 37 days

Measurement PerformanceThe Importance of Resolution

1.5

2.0

2.5

3.0

3.5

Re

solu

tio

n (

mic

ron

s)RPCM Metal Loss Resolution vs Pipe Diameter

1.5

2.0

2.5

3.0

3.5

Re

solu

tio

n (

mic

ron

s)RPCM Metal Loss Resolution vs Pipe Diameter

Filter Time Constant ~ 3 hours

13

0.0

0.5

1.0

0 5 10 15 20 25 30 35 40

Re

solu

tio

n (

mic

ron

s)

Pipe Diameter

300 bar 600 bar

0.0

0.5

1.0

0 5 10 15 20 25 30 35 40

Re

solu

tio

n (

mic

ron

s)

Pipe Diameter

300 bar 600 bar

• Low pass 1st order filter with TC ~ 3 hours

• Resolution determined by magnitude of resistance

• Relatively insensitive for large pipe diameters

(inches)

400

500

600

700

800

Met

al L

oss

(M

icro

ns)

Sector 1Sector 2Sector 3

RPCM Sector Data

12

3

45

6

7

8

Measurement PerformanceTop-of-Line Corrosion Case Study

3

14

• Stratified flow / high temp

• Dissolved CO2 / H2S

• Cold spots are vulnerable

• Organic acids (acetic, HCl)

• BOL protected by inhibitor

0

100

200

300

0 100 200 300 400

Days

Met

al L

oss

(M

icro

ns)

Sector 4

Sector 5Sector 6Sector 7

5

Case StudyCoP Judy Jade North Sea 2001

15

2 x 16” Spool flanged into SSV

Case StudyCoP Judy Jade North Sea 2001

16

Performance of subsea spool after 5 years continuous

operation

• RPCMs have extensive field history

• Widely accepted technology for

subsea pipeline corrosion monitoring

• Full circumferential view

• Versatile configuration – allows

monitoring of: PWC, other alloys,

Conclusions

17

monitoring of: PWC, other alloys,

pitting etc

• Flexible platform for other

measurements

– PT

– Conductivity (EIS)

– Single Phase Flow

• Resolution circa 1 micron (near real-

time)

Thank you for your attention!

18