Autoclaves Approximating test vessel compositions defined in - PowerPoint PPT Presentation

Autoclaves Approximating test vessel compositions defined in NACE/ISO corrosion testing standards AJ Gerbino OL OLI Simulati ation on Conf nfer eren ence ce 2016 Conference organization by

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 H 2 S and CO 2 loading • Fixed application range • Software approach to calculate H 2 S and CO 2 loading • Reduce or eliminate limits to gas loading • Address flexibility limits to accommodate experiments

• TM0185 - • ANSI/NACE TM0284 - • NACE TM0296 - • NACE TM0198 - • ANSI/NACE TM0177 - • ANSI/NACE MR0175/ISO15156-2 - ANSI/NACE/ISO test methods Highlights of each method presented

TM0185 - Evalu luation of in internal l pla lastic ic coatin ings for corrosion control of tubula lar goods by y autoclave testin ing • 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 - Evalu luation of pip ipelin line and pressure vessel l steels ls for resis istance to H-in induced crackin ing • 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 • H 2 S or H 2 S/CO 2 bubbled continuously to maintain constant PP • 27-page document, very detailed regarding sample and analysis

TM0296 - Evalu luatin ing Ela lastomeric materia ials in in sour liq liquid id envir ironments • 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 – Slo Slow str train in rate tes est method for r screening CRA for r str tress corr rrosion cracking in in so sour oilf ilfield se serv rvices • No specified water composition. • Water is 80% of volume • Gas mixture of CO 2 ,H 2 S, N 2 , Ar, or CH 4 • No test T and P defined

TM0177- Lab testin ing for resis istance to SSC and SCC in in H 2 S envir ironments • Four test solutions • Test gas usually mixture; H2S, CO2, Ar, N2 • Test gas replenished to maintain P H2S • Continuous gas bubbling an option at test T/P • <75% liquid volume

MR0175 - Petrole leum and materia ial gas in industries - materials ls for use in in H2S-containing envir ironments • Initial publication 1975 • Provides estimates for determining P H2S and pH Annex D – determining pH Annex C – determining P H2S P T ,MPa Y H2S ,ppmV

Summary ry of f 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

J.L. Crolet and M.R. Bonis. 2000. How to pressurize Autoclaves for Corrosion testing under CO 2 and H 2 S Pressure . Corrosion 56(2) pp. 167-182 Alg lgebraic method to lo load a sealed autoclave Approach for resolving the major limitation of achieving target H2S and CO2 at HPHT

Crolet/Bonis method • Defines S H2S , S CO2 (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 S G for each component • Gas concentration in gas (mmol/L gas -bar) • Computes total moles H 2 S/CO 2 in vapor and water • Includes an adjustment for Gas-Liquid loading ratio

S H2S , S CO2 (m (mmol/l-bar) physical solu lubility coefficient S values are obtained from linear fit of solubility data S H2S at 38C S CO2 @ 100C 2000 250 y = 68.2*PH2S (mmol/L-bar) y = 10.5*PCO2 (mmol/L-bar) 1600 200 CO2, mmol/L H2S, mmol/l 1200 150 800 100 400 50 Ref #1 Ref #2 0 0 0 10 20 30 0 5 10 15 20 25 PH2S, bar PCO2, bar

T-dependent S S H2S , , S CO2 , , and S G AQ Fwk MSE Fwk 100.0 100 S H2S S H2S S CO2 S CO2 S G S G S H2S (OLI) S CO2 (OLI) S H2S (OLI) S G (=1000/RT) S CO2 (OLI) 0.0 0 0 200 0 200 S_H2S (fug) S CO2 and S H2S units are mmol/L-bar S G units are mmol/L(vapor)-bar = same for all gases

H 2 S/CO 2 Loading using Crolet and Bonis’ algebraic method “Gas moles moles Total moles “Physical Gas-Liquid = = solubility” H2S in H2S in solubility” volume H2S in based on gas Liquid vapor (mol/l-bar) ratio autoclave law (1/RT) Example application, H 2 S loading in 1L autoclave vessel with different GLR Case T S H2S S G P H2S V L V G GLR M H2S,L M H2S,V X H2S * 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 * Authors define X H2S as dissolved H 2 S in Similar equation for CO2 loading water

Algebraic method transitioning to OLI calculations • Method for P CO2 and P H2S . Carrier gases are omitted. • S H2S , S CO2 values based on linear portion of solubility curve. Solubility is non-linear at higher pressures • Method excludes H 2 S/CO 2 partitioning to oil phase • Any aqueous reactions are ignored 3000 H2S (mmol/L) = 40*PH2S 2500 2000 H2S, mM 1500 93C data 1000 500 Ref #3 0 0 20 40 60 80 100 PH2S (bar)

OLI I Studio and Flo lowsheet 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 H 2 S bubbling • P N2 in headspace following purge step • target P H2S , P CO2 , at test • target C H2S , C CO2 at test (client specific) • Target P H2S , P CO2 after test depressurizing (client specific) • P H2S,ambient and P CO2,ambient to achieve target P H2S and P CO2 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 P CO2 , P H2S , loading • Does not accomplish • H 2 S and CO 2 loading pressure • Individual phase volume • Individual phase composition • Sample volume • OLI Studio Analyzer. Single Point Calculation type

OLI Studio – Basic Autoclave calc.

Option #2 Flo lowsheet TMO198 Stress testing in CaCl2 brine • Configuration Specifications • Four Flow controllers - Four valves V T =0.5L • Six mixers (7 th for measurement only) V L =0.4L CaCl2 • Three pressure controllers V specimin =not included P H2S , depressurized =15% • Accomplishes P CO2 , depressurized =9% • P H2S and P CO2 loading pressures P test =2000psia • individual phase compositions T test =149 • more complicated software is required View Software

Flowsheet ESP approach

Option #3 - OLI I Studio Mix ixers in in seri ries • 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 • H 2 S, CO 2 , N 2 inflows (multipliers) in Steps 3, 4, and 5 mixers adjusted manually until pp targets in Step 6 are met • Accomplishes • P H2S and P CO2 loading pressures • individual phase compositions • Does not accomplish • The user is the flow controller • Mixer inflows are limited to multipliers, not View Software volume

OLI Studio – Cascading Mixers

Summary ry • 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 Partial list of clients/colleagues that have provided advice, information, or direction on developing a better autoclave simulation application in OLI software • Brent Sherar, Blade Energy • Rudy Hausler, Blade Energy • Tracey Jackson, Baker Hughes • Pilan Esteban, Tubacex • George Winning, Element