Experiences of internal inspection of pipelines in

the Ekofisk Field

Tananger: 09.12.2009.

AGENDA

•What is needed to keep aging pipelines

healthy

•Cleaning pig types used

•Inspection technologies

•Data Quality and reporting

Internal Maintenance and Monitoring

programs

Continous treatment with biocide and corrosion

inhibitor

Monitoring with coupons and probes.

Product Sampling

Control of BS&W.

Batch treatment with chemicals

Regular cleaning pig programs.

Types of cleaning pigs used at Ekofisk

Foam pig for light

cleaning, stuck pigs, and

verification of pigability.

BI-DI for removal of wax,

biofilm, scale build up.

Types of cleaning pigs used at Ekofisk

Pit-Boss – more aggressive

cleaning, hard wax, more

scale

Pencil brush pig.

Tiger Tools

Agressive cleaning,

Hard scale, corrosion products

Cleaning pig Interval

• Weekly

• Bi-Weekly

• Monthly

• Yearly

• Extra cleaning prior to internal inspection

Regular Internal Inspections

• Base case is internal inspection every 5th year

• Inspection results are used to optimize program

(risk based)

• Intervals from every 3rd month to every 10th

year

Use of different technologies for internal

inspections.

• Every 5th year – MFL

• Gasslines – MFL

• Three Phase lines – MFL

• When features above 70%wt loss – UT

• Water Injection lines - UT

• Pipelines of extreme importance / significant risk

UT alternating with MFL

Dual inspections/alternating years

MFL – Magnetic Flux Leakage

Spec: 10% +/- on measurement accuracy, 85%

confidence level

Qualitative analysis

Can be used in almost all piggable lines

Excellent automatic screening system, handles huge

amount of data, no threshold

Speed range from 0.4 – 4m/s

Superior on small pittings

MFL – Magnetic Flux Leakage

Less efficient on thick wall pipes

Speed limitations

Gas pipelines with low pressure causes problems

Difficulties with channeling corrosion

UT- Ultrasound Pig

Spec: +/- 0.2mm on measurement accuracy, 95%

confidence level

Direct measurements/analysis

Good quality on data in thick walled pipelines

No problems with findings

under extra sleeves

Speed range from

0.1 – 4.5m/s

Superior on

channeling

corrosion

Combined wt and crack detection

pig

Crawler, Tethered tool.

Same spec as UT pig.

Ultimate choice for unpiggable pipelines.

lack of launchers/receivers

Dual diameter pipelines with large difference in

dia.

Restrictions in pipeline

Requires – liquid filled lines

Limitation on length of tether/wire

Quality of inspection data

• Data quality is dependent on equipment,

cleaning and speed

• MFL – needs less cleaning than UT.

Tolerates some level of wax and scale

Flow between 0.4m/s and 4.0m/s

• UT needs pristine clean pipeline

No gas bubbles

Scale < 1mm

Experience wax problems well before MFL.

Analysis

• Automatic analysis not enough – needs manual sizing in

addition

•Only manual sizing reduces the number of reported features

due to time/cost

•Vendor needs a strong analysis team with lots of experience.

•Need good basis in verifications of findings (dig-ups& pull

through)

•No good with good analysis and poor reporting.

Reporting.

• Standard reporting:

> 10% wt, automatic sizing / threshold of 10%, 10 features pr km.

• Copsas require ALL defects to be reported – on a best endavour basis

•Requests runcom reports for all lines.

• Manual sizing of the most serious ML from last run, and any new

significant ML (deep, ERF, rapid growth)

• No requirement of number of defects to be reported for runcom

• Decision based on pipeline, defects, growth etc.

Conclusion

•MFL first choice for untroubled pipelines/low level

corrosion

•Gas and multiphase pipelines

•Pipelines with pitting corrosion

•UT first choice for pipelines with deep corrosion

•With channeling corrosion

•Un-piggable pipelines

•For pipelines of extreme importance/very high corrosion

rate

•DUAL INSPECTIONS

Ready for Inspection