Suncor Firebag Wellhead Integrity Discussion
Suncor Firebag Wellhead Integrity Discussion Trent Pehlke – Suncor Energy In-Situ Production Engineer Nov 3, 2014
Table of Contents • • • • •
10
Introduction Wellhead and Gate Valve Design Operating Conditions Failure Analysis Recommendations and Going Forward
Introduction – Firebag • Operating for 11 years • 140 producing wells – 35 “Infill” wells • Producing ~ 180,000 bbl/d – Average 930m3/d per well • Injecting ~ 75,000m3/d steam
10
Introduction – Wellhead Integrity • Integrity Definition – Application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well • Firebag Wellhead Integrity Issue: – Wellhead gate valves passing (leaking) internally during workovers • Unable to isolate/kill the well until it is replaced • Safety concerns • Maintenance procedure concerns 10
Wellhead Design
Gate Valves
Gate Valve Design
Gate Valve Design – Positions Gate Open
Gate Closed
Gate Travelling
Component Materials • Gate Face: – AISI 4130 Alloy Steel with Nitride hardened surface – AISI 4130 Alloy Steel with Deloro-40 Hard Face (Nickel based) surface
• Stem: – AISI 4140 Alloy Steel
• Seat Face: – AISI 4130 Alloy Steel Hard Faced with Stellite (Cobalt-based)
Well Operating Conditions (Typical Ranges) • Injector: – Pressures: 2000-3500KPa – Temperatures: 240C
• Producer: – Pressures: 800-1400KPa – Temperatures: 100-200C
• Fluid/Gas Components: – CO2: 20-30% – H2S: 2-10% – Cl: 85ppm
2S6 External Images Failure Analysis – Visual Valve Assembly Gate Guides
Grease Packing
Upper and lower grease ports
10
2S6 Gate Images – Visual Gate Assembly Failure Analysis
Surface Corrosion
11 Gate Assembly
8P11 Images Failure Analysis – Visual Stem and Bearing
12
Failure Analysis – Ludwigs Visual Analysis • Gate Face: – Varying thickness pale-bronze scale – After cleaning, corrosion was observed on the surface • Deloro-40 HF thickness reduced from 0.062” to 0.015”
• Seat: – No scale or corrosion found on the face – Corrosion and scale deposits noted in the bore and sealant groove
• Stem: – Dark/tarnished appearance – Rust scale – Pitting
Failure Analysis – Scale • Energy Dispersive X-Ray (EDX) Analysis – Gate: Ni 41%, O 14%, C 13%, Fe/S 12%, Cr 7% – Seat: Fe 36%, C 30%, O 22%, S 4%, Ca/Mo 3% – Stem: C 41%, O 27%, Fe/Si 6%, S 4%, Cr/Mg/Mo 3%
• X-Ray Diffraction (XRD) Analysis – Gate: 𝑁𝑖𝑆, 𝑁𝑖3 𝑆2 , 𝐹𝑒𝐶𝑟2 𝑂4 , 𝑁𝑖7 𝑆6 , 𝐹𝑒3 𝑂4 – Seat: 𝐹𝑒3 𝑂4 ,Ca𝐶𝑂3 , Mo𝑆2 , Fe𝑆2 , 𝐴𝑙2 𝑆𝑖2 𝑂5 (𝑂𝐻)4 – Stem: 𝐹𝑒3 𝑂4 , Ca𝐶𝑂3 , Mo𝑆2 , 𝐴𝑙2 𝑆𝑖2 𝑂5 (𝑂𝐻)4
Failure Analysis – Corrosion Analysis • Corrosion Analysis – Gate Face: • Aqueous H2S corrosion • Nickel and nickel-rich alloys can be susceptible to H2S attack – Seat: • Seat face exhibited no corrosion or wear • Aqueous H2S/CO2 corrosion and aqueous oxidation (pitting) found on the seat bore and in the sealant groove – Promoted by crevice corrosion – Stem: • Aqueous H2S/CO2 corrosion
Failure Analysis – Conclusions • Maintenance Procedure Concerns • Unexpectedly high concentrations of produced CO2/H2S compared to initial beliefs • Stellite finished components found not corroding
Recommendations and Going Forward • Improve maintenance procedures • Select alternative gate face materials – AISI 4130 Alloy Steel treated with Stellite HF (Cobalt-based)
• Install corrosion coupons for material and corrosion analysis • Valve body fluid sampling
Questions?
Acid Gas Sources
Acid Gas Sources • Hydrocarbon biodegradation – Microbes + hydrocarbon + nutrients CH4 + CO2 + Other Products (Pyrite)
• Aquathermolysis – Decarboxylation CO2 – Hydrolysis H2S
• TSR (Thermochemical Sulfate Reduction) – Breakdown of anhydrite (CaSO4) scales at high temps
• Microbe Bacteria – Sulfate Reducing Bacteria (SRB), and Acid Producing Bacterial (APB)
Acid Gas Corrosion
Aqueous Acid Gas Corrosion • H2S – When H2S is dissolved in water it is a weak sulphuric acid and is corrosive – Forms a protective scale (FeS) at low temps, deteriorates >120C – At higher temps the scale is cathodic in relation to the casing and galvanic corrosion occurs
• CO2 – – –
Corrosive when dissolved in water Must first hydrate to carbonic acid (H2CO3) before it becomes acidic Protective scale >150C
Acid Gas Corrosion
Aqueous Acid Gas Corrosion • Dominant mechanism and rate depend on: – CO2:H2S – Temperature – Pressure – pH
Failure Economics • 83 valve failures in 2013 • •
•
•
– Cost: $245K 57 valve failures in 2014 YTD – Cost: $120K Average repair costs: $2,000/valve – NOT including lost rig time % of valves checked with issues – 2013: 26% – 2014 YTD: 17% Approximate cost of upgrading: $1,550-$3,700/valve
Legal • Suncor Energy Inc. and its affiliates (collectively "Suncor") do not make any express or implied representations or warranties as to the accuracy, timeliness or completeness of the statements, information, data and content contained in this presentation and any materials or information (written or otherwise) provided in conjunction with this presentation (collectively, the "Information"). The Information has been prepared solely for informational purposes only and should not be relied upon. Suncor is not responsible for and is hereby released from any liabilities whatsoever for any errors or omissions in the Information and/or arising out of a person’s use of, or reliance on, the Information. 10
Table of Contents • • • • •
10
Introduction Wellhead and Gate Valve Design Operating Conditions Failure Analysis Recommendations and Going Forward
Introduction – Firebag • Operating for 11 years • 140 producing wells – 35 “Infill” wells • Producing ~ 180,000 bbl/d – Average 930m3/d per well • Injecting ~ 75,000m3/d steam
10
Introduction – Wellhead Integrity • Integrity Definition – Application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well • Firebag Wellhead Integrity Issue: – Wellhead gate valves passing (leaking) internally during workovers • Unable to isolate/kill the well until it is replaced • Safety concerns • Maintenance procedure concerns 10
Wellhead Design
Gate Valves
Gate Valve Design
Gate Valve Design – Positions Gate Open
Gate Closed
Gate Travelling
Component Materials • Gate Face: – AISI 4130 Alloy Steel with Nitride hardened surface – AISI 4130 Alloy Steel with Deloro-40 Hard Face (Nickel based) surface
• Stem: – AISI 4140 Alloy Steel
• Seat Face: – AISI 4130 Alloy Steel Hard Faced with Stellite (Cobalt-based)
Well Operating Conditions (Typical Ranges) • Injector: – Pressures: 2000-3500KPa – Temperatures: 240C
• Producer: – Pressures: 800-1400KPa – Temperatures: 100-200C
• Fluid/Gas Components: – CO2: 20-30% – H2S: 2-10% – Cl: 85ppm
2S6 External Images Failure Analysis – Visual Valve Assembly Gate Guides
Grease Packing
Upper and lower grease ports
10
2S6 Gate Images – Visual Gate Assembly Failure Analysis
Surface Corrosion
11 Gate Assembly
8P11 Images Failure Analysis – Visual Stem and Bearing
12
Failure Analysis – Ludwigs Visual Analysis • Gate Face: – Varying thickness pale-bronze scale – After cleaning, corrosion was observed on the surface • Deloro-40 HF thickness reduced from 0.062” to 0.015”
• Seat: – No scale or corrosion found on the face – Corrosion and scale deposits noted in the bore and sealant groove
• Stem: – Dark/tarnished appearance – Rust scale – Pitting
Failure Analysis – Scale • Energy Dispersive X-Ray (EDX) Analysis – Gate: Ni 41%, O 14%, C 13%, Fe/S 12%, Cr 7% – Seat: Fe 36%, C 30%, O 22%, S 4%, Ca/Mo 3% – Stem: C 41%, O 27%, Fe/Si 6%, S 4%, Cr/Mg/Mo 3%
• X-Ray Diffraction (XRD) Analysis – Gate: 𝑁𝑖𝑆, 𝑁𝑖3 𝑆2 , 𝐹𝑒𝐶𝑟2 𝑂4 , 𝑁𝑖7 𝑆6 , 𝐹𝑒3 𝑂4 – Seat: 𝐹𝑒3 𝑂4 ,Ca𝐶𝑂3 , Mo𝑆2 , Fe𝑆2 , 𝐴𝑙2 𝑆𝑖2 𝑂5 (𝑂𝐻)4 – Stem: 𝐹𝑒3 𝑂4 , Ca𝐶𝑂3 , Mo𝑆2 , 𝐴𝑙2 𝑆𝑖2 𝑂5 (𝑂𝐻)4
Failure Analysis – Corrosion Analysis • Corrosion Analysis – Gate Face: • Aqueous H2S corrosion • Nickel and nickel-rich alloys can be susceptible to H2S attack – Seat: • Seat face exhibited no corrosion or wear • Aqueous H2S/CO2 corrosion and aqueous oxidation (pitting) found on the seat bore and in the sealant groove – Promoted by crevice corrosion – Stem: • Aqueous H2S/CO2 corrosion
Failure Analysis – Conclusions • Maintenance Procedure Concerns • Unexpectedly high concentrations of produced CO2/H2S compared to initial beliefs • Stellite finished components found not corroding
Recommendations and Going Forward • Improve maintenance procedures • Select alternative gate face materials – AISI 4130 Alloy Steel treated with Stellite HF (Cobalt-based)
• Install corrosion coupons for material and corrosion analysis • Valve body fluid sampling
Questions?
Acid Gas Sources
Acid Gas Sources • Hydrocarbon biodegradation – Microbes + hydrocarbon + nutrients CH4 + CO2 + Other Products (Pyrite)
• Aquathermolysis – Decarboxylation CO2 – Hydrolysis H2S
• TSR (Thermochemical Sulfate Reduction) – Breakdown of anhydrite (CaSO4) scales at high temps
• Microbe Bacteria – Sulfate Reducing Bacteria (SRB), and Acid Producing Bacterial (APB)
Acid Gas Corrosion
Aqueous Acid Gas Corrosion • H2S – When H2S is dissolved in water it is a weak sulphuric acid and is corrosive – Forms a protective scale (FeS) at low temps, deteriorates >120C – At higher temps the scale is cathodic in relation to the casing and galvanic corrosion occurs
• CO2 – – –
Corrosive when dissolved in water Must first hydrate to carbonic acid (H2CO3) before it becomes acidic Protective scale >150C
Acid Gas Corrosion
Aqueous Acid Gas Corrosion • Dominant mechanism and rate depend on: – CO2:H2S – Temperature – Pressure – pH
Failure Economics • 83 valve failures in 2013 • •
•
•
– Cost: $245K 57 valve failures in 2014 YTD – Cost: $120K Average repair costs: $2,000/valve – NOT including lost rig time % of valves checked with issues – 2013: 26% – 2014 YTD: 17% Approximate cost of upgrading: $1,550-$3,700/valve
Legal • Suncor Energy Inc. and its affiliates (collectively "Suncor") do not make any express or implied representations or warranties as to the accuracy, timeliness or completeness of the statements, information, data and content contained in this presentation and any materials or information (written or otherwise) provided in conjunction with this presentation (collectively, the "Information"). The Information has been prepared solely for informational purposes only and should not be relied upon. Suncor is not responsible for and is hereby released from any liabilities whatsoever for any errors or omissions in the Information and/or arising out of a person’s use of, or reliance on, the Information. 10
