OLI Simulation Conference 2016

Conference organization by

Autoclaves Approximating test vessel compositions defined in NACE/ISO corrosion testing standards

AJ Gerbino

Topics

• NACE Standards – general overview • Read up on standards to see what clients were preparing

in lab

• Significant discretion in formulating experiment

• Algebraic method to calculate H2S and CO2 loading • Fixed application range

• Software approach to calculate H2S and CO2 loading • Reduce or eliminate limits to gas loading

• Address flexibility limits to accommodate experiments

ANSI/NACE/ISO test methods Highlights of each method presented

• TM0185 -

• ANSI/NACE TM0284 -

• NACE TM0296 -

• NACE TM0198 -

• ANSI/NACE TM0177 -

• ANSI/NACE MR0175/ISO15156-2 -

TM0185 - Evaluation of internal plastic coatings for corrosion control of tubular goods by autoclave testing

• No autoclave specifications

• Test T/P left to the investigator

• At least 25% oil, water, and gas in vessel

• Oil is 50/50 toluene/kerosene

• Water is fresh or brine

• Gas is single or multicomponent

• 3-page document, few details, no apparatus image

TM0284 - Evaluation of pipeline and pressure vessel steels for resistance to H-induced cracking

• Not an Autoclave test – ambient P and T

• Four water options • A: NaCl + HAc + H2S bubbling – 2.7 to 3.2pH

• B: Synthetic Seawater +H2S bubbling – 4.8 to 5.4pH

• C: NaCl + NaAc +H2S/CO2 bubbling – target pH

• D: TM0177 solution B

• Minimum liquid volume per sample area

• H2S or H2S/CO2 bubbled continuously to maintain constant PP

• 27-page document, very detailed regarding sample and analysis

TM0296 - Evaluating Elastomeric materials in sour liquid environments

• Fixed volume ratios • Water=5%

• Oil=60%

• Sample <4%

• Gas = balance

• Water composition not defined

• Three HC compositions (alkanes, kerosene)

• Two Gas mixtures (H2S up to 20%)

• Test T 100-175C, Test P 6.75MPa

• O2 purging (all standards describe this)

• Autoclave required

TM0198 – Slow strain rate test method for screening CRA for stress corrosion cracking in sour oilfield services

• No specified water composition.

• Water is 80% of volume

• Gas mixture of CO2,H2S, N2, Ar, or CH4

• No test T and P defined

TM0177- Lab testing for resistance to SSC and SCC in H2S environments

• Four test solutions

• Test gas usually mixture; H2S, CO2, Ar, N2

• Test gas replenished to maintain PH2S

• Continuous gas bubbling an option at test T/P

• <75% liquid volume

MR0175 - Petroleum and material gas industries - materials for use in H2S-containing environments

• Initial publication 1975 • Provides estimates for determining PH2S and pH

Annex C – determining PH2S Annex D – determining pH

YH2S,ppmV

PT,

MPa

Summary of method limitations, uncertainties • Major limitations –

• Setting target properties at elevated T and P when loading is performed at ambient conditions

• Minor limitations – • Liquids loading effects on gas partitioning

• Formulated water properties

• Remaining headspace composition following N2 purging

Algebraic method to load a sealed autoclave Approach for resolving the major limitation of achieving target H2S and CO2 at HPHT

J.L. Crolet and M.R. Bonis. 2000. How to pressurize Autoclaves for Corrosion testing under CO2 and H2S Pressure. Corrosion 56(2) pp. 167-182

Crolet/Bonis method

• Defines SH2S, SCO2 (mmol/L-bar) • a “Physical Solubility” term

• Units of molar gas concentration in water per partial pressure

• Also referred to as an inverse Henry’s constant

• Defines a similar term SG for each component • Gas concentration in gas (mmol/Lgas-bar)

• Computes total moles H2S/CO2 in vapor and water

• Includes an adjustment for Gas-Liquid loading ratio

SH2S, SCO2 (mmol/l-bar) physical solubility coefficient

SH2S at 38C SCO2 @ 100C

y = 68.2*PH2S (mmol/L-bar)

0

400

800

1200

1600

2000

0 10 20 30

H2

S, m

mo

l/l

PH2S, bar

y = 10.5*PCO2 (mmol/L-bar)

0

50

100

150

200

250

0 5 10 15 20 25

CO

2, m

mo

l/L

PCO2, bar

S values are obtained from linear fit of solubility data

Ref #1 Ref #2

0.0

100.0

0 200 0

100

0 200

S_H2S (fug)

T-dependent SH2S , SCO2 , and SG

AQ Fwk MSE Fwk

SCO2 and SH2S units are mmol/L-bar SG units are mmol/L(vapor)-bar = same for all gases

SH2S

SCO2

SG

SH2S

SCO2

SG

SH2S (OLI)

SH2S (OLI)

SCO2 (OLI)

SCO2 (OLI)

SG (=1000/RT)

H2S/CO2 Loading using Crolet and Bonis’ algebraic method

Total moles H2S in

autoclave

moles H2S in Liquid

moles H2S in vapor

= = “Physical solubility” (mol/l-bar)

“Gas solubility” based on gas law (1/RT)

Gas-Liquid volume ratio

Case T SH2S SG PH2S VL VG GLR MH2S,L MH2S,V XH2S*

C mmol/l-bar bar L L mmoles mmoles mmol/L

1 30 75 39.7 0.01 0.5 0.5 1.0 0.4 0.2 0.6 2 60 35 36.1 0.003 0.8 0.2 0.3 0.1 0.0 0.1

3 100 21 31.4 0.04 0.3 0.7 2.3 0.3 0.9 1.1

4 150 18 28.4 0.7 0.2 0.8 4.0 2.5 15.9 18.4

Example application, H2S loading in 1L autoclave vessel with different GLR

* Authors define XH2S as dissolved H2S in

water Similar equation for CO2 loading

Algebraic method transitioning to OLI calculations • Method for PCO2 and PH2S. Carrier gases are omitted.

• SH2S, SCO2 values based on linear portion of solubility curve. Solubility is non-linear at higher pressures

• Method excludes H2S/CO2 partitioning to oil phase

• Any aqueous reactions are ignored

H2S (mmol/L) = 40*PH2S

0

500

1000

1500

2000

2500

3000

0 20 40 60 80 100

H2

S, m

M

PH2S (bar)

93C data

Ref #3

OLI Studio and Flowsheet ESP on Standard methods Incorporating Mass balance & phase-partitioning to fill the void from the algebraic method limit

Specifications/Requirements

• Tool must enable • Water, oil and gas formulations

• Water and oil loading volumes

• Sample loading volume

• Tool must calculate • target pH before loading or after H2S bubbling

• PN2 in headspace following purge step

• target PH2S, PCO2, at test

• target CH2S, CCO2 at test (client specific)

• Target PH2S, PCO2 after test depressurizing (client specific)

• PH2S,ambient and PCO2,ambient to achieve target PH2S and PCO2 at test

Complications

• Reagent and Test procedure is multi-step

• Some steps are cyclical, requiring iterations

• Some steps are not easy to create in a simulator tool

Option #1 - Single-Point Autoclave

• Accomplishes • Final PCO2, PH2S, loading

• Does not accomplish • H2S and CO2 loading pressure

• Individual phase volume

• Individual phase composition

• Sample volume

• OLI Studio Analyzer. Single Point Calculation type

OLI Studio – Basic Autoclave calc.

Option #2 Flowsheet • Configuration

• Four Flow controllers - Four valves • Six mixers (7th for measurement only) • Three pressure controllers

• Accomplishes • PH2S and PCO2 loading pressures • individual phase compositions

• more complicated software is required

Specifications VT=0.5L VL=0.4L CaCl2 Vspecimin=not included PH2S,depressurized=15% PCO2,depressurized=9% Ptest=2000psia Ttest=149

TMO198 Stress testing in CaCl2 brine

View Software

Flowsheet ESP approach

Option #3 - OLI Studio Mixers in series • Configuration

• Six mixers, one for each autoclave charging and heating step

• Flowsheet pressure controllers are replaced by new isochoric calculation

• Manual iterations to converge case • Autoclave Step 6 (mixer) is calculated • H2S, CO2, N2 inflows (multipliers) in Steps

3, 4, and 5 mixers adjusted manually until pp targets in Step 6 are met

• Accomplishes • PH2S and PCO2 loading pressures

• individual phase compositions

• Does not accomplish • The user is the flow controller • Mixer inflows are limited to multipliers, not

volume View Software

OLI Studio – Cascading Mixers

Summary

• NACE documents appear to be more guidelines than specific instructions, and clients have experimental latitude

• Apply electrolyte software to address limits to achieving target properties in ANSI/ASTM/NACE methods and user-modified methods

• Single-point Autoclave application range is limited

• Complete simulation possible using Flowsheet software

• Using the mixers in OLI Studio with isochoric calculation expands the OLI Studio range

Acknowledgement

• Brent Sherar, Blade Energy

• Rudy Hausler, Blade Energy

• Tracey Jackson, Baker Hughes

• Pilan Esteban, Tubacex

• George Winning, Element

Partial list of clients/colleagues that have provided advice, information, or direction on developing a better autoclave simulation application in OLI software

References Slide Ref # Reference

4 TM0185 - Evaluation of internal plastic coatings for corrosion control of tubular goods by autoclave testing

5 ANSI/NACE TM0284 - Evaluation of pipeline and pressure vessel steels for resistance to Hydrogen-induced cracking

6 NACE TM0296 - Evaluating Elastomeric materials in sour liquid environments

7 NACE TM0198 - Slow strain rate test method for screening CRA for stress corrosion cracking in sour oilfield services

8 ANSI/NACE TM0177 - Laboratory testing of metals for resistance to sulfide stress cracking and stress corrosion cracking in H2S environments

9 ANSI/NACE MR0175/ISO15156-2 - Petroleum and material gas industries – materials for use in H2S-containing environments in oil and gas production. Part 2: cracking-resistant carbon and low-alloy steeps and the use of cast iron

11 1 Selleck F. T., et al, "Phase Behavior in the H2S - Water System", Ind. and Eng. Chem., 44, (9), 2219-2226, 1952 (plus two additional sources). Gillespie P. C., Owens J. L., Wilson G. M., "Sour Water Equilibria Extended to High T and with Inerts Present", AIChE Winter National Mtg Atlanta, 1984.

11 2 Muller G., et al., “VLE in the Ternary System NH3– CO2–H2S at High Water Contents in the Range 373 K to 473 K", Berichte der Bunsen Gesellschaft fur Physik. Chm., 92(2), 148-160, 1988.

14 3 Gillespie P. C., Owens J. L., Wilson G. M., "Sour Water Equilibria Extended to High Temperatures and With Inerts Present", AIChE Winter National Meeting Atlanta, 1984.