Fatigue Performance of High Strength Riser Materials
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Fatigue Performance of High Strength Riser Materials RPSEA Project No. DW 1403 TAC Quarterly Meeting June 2, 2009 Houston, Texas Presented by Stephen J. Hudak, Jr. Materials Engineering Department Southwest Research Institute. Research Partnership to Secure Energy for America.

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Fatigue Performance of High Strength Riser Materials

RPSEA Project No. DW 1403

TAC Quarterly Meeting

June 2, 2009

Houston, Texas

Presented by

Stephen J. Hudak, Jr.

Materials Engineering Department

Southwest Research Institute

Research Partnership to Secure Energy for America


Project objective
Project Objective

  • Assess the fatigue resistance of new high strength HPHT riser materials in representative environments

  • Fatigue Crack Growth Rates (FCGR)

  • Classical S-N fatigue life

  • Environments

    • Air (baseline)

    • Sour brine

    • Seawater


Materials
Materials

MaterialYS, ksiSourStatus

1 114 ksi yes Specimens machined; frequency-scan tests complete

2 131 ksi yes Specimens machined; frequency-scan tests complete

3 ~125 ksi yes Awaiting material

4 132 ksi no Specimens machined; frequency-scan tests complete

5 156 ksi no Specimens being machined

6 ~120 ksi yes Awaiting material


Environments
Environments

  • Lab air (baseline): 70-75°F, 40-60% RH

  • Seawater: ASTM D1141 substitute ocean water open to the air with cathodic protection: - 1050mv vs. Saturated Calomel Electrode

  • Sour Brine: Production brine with oxygen below 10 ppb and 35% H2S + 65% CO2


Task 1 fcgr testing
Task 1: FCGR Testing

  • Frequency scan (FS) tests at Constant-DK to determine optimum cyclic loading frequency for subsequent testing

  • FCGR testing as a function of DK to determine cracking kinetics that can be used in fracture mechanics design and/or fitness-for-service assessments



Task 1 fcgr test matrix
Task 1: FCGR Test Matrix

  • Total FCGR tests 10 15 9+3 Grand Total: 34+3

    • Orange = tests completed

    • Red = tests not in current SOW

* Materials in-hand


Frequency scan testing
Frequency Scan Testing

Seawater

  • Corrosion fatigue performance sensitive to loading frequency

  • Fatigue crack growth rates at constant-DK used to characterize frequency effect in frequency scan (FS) tests

13x


Seawater vs sour brine
Seawater vs. Sour Brine

Seawater

YS = 114 ksi

Sour Brine

6X

24X


Seawater vs sour brine1
Seawater vs. Sour Brine

Seawater

YS = 131 ksi

SourBrine

15X

250X


Material environment interactions
Material-Environment Interactions

Corrosion-Fatigue Acceleration* vs. Air Baseline

Yield Strength, ksi

114 131 132

Environment:

Sour Brine

Seawater

24X 250X ---

6X 15X 15X

* At DK= 20 ksi√in. R=0.5 and Frequency = 0.01 Hz


Frequency response vs ys
Frequency Response vs. YS

Sour Brine

Seawater

Air Baseline

Air Baseline


Last quarter progress
Last-Quarter Progress

  • Procured four of six test materials – at no cost to project

  • Completed specimen machining on three of six materials

  • Specimen machining on fourth material is in-progress

  • Completed frequency scan tests on 62% of material-environment combinations

  • Analyzed frequency-scan data and identified the importance of material strength level on corrosion-fatigue resistance

  • Determined that saturation frequency likely depends on material-environment combination

  • Machined grips for baseline air tests to be performed at NETL-Albany, Oregon

  • Initiated air S-N testing at SwRI to assess inter-laboratory reproducibility with NETL

  • Took receipt of ConocoPhillips Ti-alloy data base



Costs
Costs

RPSEA Contract Amt $800K

BP Cost Share $200K

Total Contracted Amt $1,000K

Costs to Date $218K

Balance $782K


Next quarter plan
Next-Quarter Plan

  • Procure remaining two test materials

  • Machine remaining specimens

  • Complete frequency-scan tests

  • Meet with PWC to select optimum test frequencies

  • Complete air S-N tests at SwRI

  • Initiate air S-N tests at NETL

  • Initiate seawater S-N tests

  • Initiate sour brine S-N tests

  • Initiate air FCGR tests

  • Initiate seawater FCGR tests

  • Initiate sour brine FCGR tests


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