A study on the application of modern corrosion resistant alloys in the upstream oil and gas

industry – Cost optimization

Presenter : Kukuh W. Soerowidjojo Company : Sandvik Materials Technology SEA

16th – 18th August 2016

INTRODUCTION Background: • A push from the industry to have more efficient process, cost

efficient and in the same time keep the safety as paramount. • Developed understanding of fabrication, welding and

availability of duplex stainless steel family. • New grades in duplex family Contents: • Corrosion resistant materials and its mechanical and corrosion

properties • Alloying element price and cost index • Case study • Summary

OPPORTUNITY OF COST SAVING IN CRA SELECTION

Cost saving

potentials

Mechanical properties

Design change by Utilizing higher

strength

Thinner wall, less material and possibly less costly

Better CAPEX

Corrosion properties

Longer life cycle Less maintenance

Less loss of production Less operation cost

Better Present Value

with Less OPEX

Alloy selection based on alloying element

selection

Less expensive alloying element

cost Possible less costly alloy Better CAPEX

CHEMICAL COMPOSITIONS OF CRA’S

UNS # Main alloying elements

PRE Ni Cr Mo N

UNS S30403 8.0 - 12.0 18.0 - 20.0 max 0.1 20 UNS S31603 10.0 -14.0 16.0 - 18.0 2.0 - 3.0 max 0.1 25 UNS S32304 3.0 - 5.5 21.5 - 24.5 0.05 - 0.60 0.05 - 0.20 25 UNS S32101 1.35 - 1.70 21.0 - 22.0 0.10 - 0.80 0.20 - 0.25 27 UNS N08904 23.0 - 28.0 19.0 - 23.0 4.0 - 5.0 >35 UNS S32205 4.5 - 6.5 22.0 - 23.0 3.0 - 3.5 0.14 - 0.20 >35 UNS S31254 17.5 - 18.5 19.5 -20.5 6.0 - 6.5 0.18 - 0.22 >40 UNS S32750 6.0 - 8.0 24.0 - 26.0 3.0 - 5.0 0.24 - 0.32 >40 UNS N06625 min. 58 20.0 - 23.0 8.0 - 10.0 >50 UNS S32707 5.5 - 9.5 26.0 - 29.0 4.0 - 5.0 0.30 - 0.50 >50 UNS S33207 6.0 - 9.0 29.0 - 33.0 3.0 - 5.0 0.40 - 0.60 >50

PREN = % Cr + 3.3 x % Mo + 16 x %N

COMMON CORROSION AT CRA IN OIL AND GAS OFFSHORE ENVIRONMENT

OTHER POSSIBLE CORROSION FORMS

• MIC – microbiological Induced Corrosion • Mercury stress cracking • TOL (top of line) corrosion • Erosion corrosion • Fatigue corrosion • Under insulation corrosion • Etc.

STRESS CORROSION CRACKING

CREVICE AND PITTING

0

10

20

30

40

50

60

0

20

40

60

80

100

120CCT and CPT versus PRE graph

CCTCPTPRE

Tem

pera

ture

o C (o F

)

PRE

(68)

(104)

(140)

(176)

(212)

(248)

ASTM G48 method E and F

MECHANICAL PROPERTIES

Duplex family has much higher yield strength than austenitic SS family

MECHANICAL PROPERTIES

Normal Design pressure calculation based on ASME B31.3 Temperature 40°C 40°C 40°C 40°C Grade 316/316L Alloy825 SAF2205 SAF2507 Allowable stress 20.00 23.3 30 38.7 Wall thickness tolerance % 10.0% 10.0% 10.0% 10.0% OD (mm) 12.7 12.7 12.7 12.7 Wall thickness (mm) 1.65 1.65 1.65 1.65 Allowable internal pressure (ksi) 5.160 6.011 7.740 9.984 Allowable internal pressure (bar) 356 414 534 688

Test pressure (ksi)* 7.740 9.017 11.610 14.976 Test pressure (bar)* 533.6 621.7 800.5 1,032.6 Barlow equation Burst pressure (ksi) 17.539 19.878 20.010 26.110 Burst pressure (bar) 1,209.3 1,370.5 1,379.6 1,800.2 API 5C3 Collapse pressure (ksi) 6.589 7.218 14.527 16.474 Collapse pressure (bar) 454.3 497.7 1,001.6 1,135.8

ALLOYING ELEMENTS PRICE AND COST INDEX

• Alloying elements price fluctuate over the time especially nickel and molybdenum.

• Nickel has high percentage in CRA and Molybdenum is the most expensive alloying element in CRA.

• Alloying cost index could be used as the first step of financial analysis of material selection.

• Cost of alloying element 50% -70%

CASE STUDY

A case study was conducted to propose material for : • 2 ½” (outer diameter 73.0.3 mm) drilling riser hydraulic line for 6000 psi and 8000 psi internal

pressure with austenitic UNS S31603 as the base. • Alternatives by considering both mechanical and corrosion properties. • Wall thicknesses selected are standard wall thicknesses available. • Selected materials acquire the same level or higher corrosion resistance than austenitic UNS

S31603 in seawater environment. • Lean duplex UNS S32304, duplex UNS S32205 and super duplex UNS S32750. • Other austenitic grades are not included since they all have higher alloying element cost indices.

PRESSURE CALCULATION AND PRICE INDEX

DISCUSSION

• It is necessary to combine the evaluation of engineering and financial analysis to reach a conclusion of financial benefit to choose a certain grade of material.

• Alloying elements keep changing overtime hence corrosion resistance materials price as well.

• Material with higher PRE has a higher resistance to marine environment corrosion, hence it is necessary to specify minimum PRE number in the material specification.

• Although the corrosion resistance of duplex family is well known, a few producers took more preventive action to coat high alloyed stainless steel pipes.

• In the case study, there is no standard size available for grade 316L for 8,000 psi rated system. Hence, the size is specially designed for the equipment and that may increase the price significantly.

SUMMARY • Cost saving could be reviewed from 3 different parameters i.e.

corrosion resistance, mechanical properties and alloying elements. • Alloying element prices contains 50-70% in the cost structure of end

products. • This case study only calculates the saving CAPEX by considering

both corrosion resistance and mechanical strength. • Pressure calculations are based on ASME B31.3 (2002) and it has

revealed that duplex and super duplex grades can save significant weight and could lead to cost saving.

• If there is any other additional corrosion protection in the system, it should be taken into consideration to add in the cost of acquisition.

• Finally, it is important to have life cycle calculation to justify the material selection.