blowout preventer (bop) maintenance schedule for...
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Blowout Preventer (BOP) Maintenance Schedule
for Optimal Cost and Reliability
Yang-Denis Su-Feher
PhD Student, Chemical Engineering
Mary Kay O’Connor Process Safety Center
Outline
• Motivation
• Methodology
• Results
• Conclusion
• Acknowledgement
• References
2
Motivation
3
Deepwater Horizon Blowout (2010)1,2
4
• 11 fatalities
• 17 injuries
• $40 billion loss
Location Incidents3,4
Macondo Prospect, USA Deepwater Horizon, 2010
Santa Barbara Channel, USA Union Oil, 1969
North Sea, UK Ocean Odyssey, 1988
North Sea, Norway
Ekofisk B, 1977
West Vanguard, 1985
Snorre A, 2004
Gullfaks C, 2010
Campos Basin, Brazil Enchova, 1984
Frade, 2011
Bay of Campeche, Mexico Ixtoc, 1979
5
Blowout Preventer5
6
Statistics of BOP failure
• 292 blowouts from 1980 to 20146
• Corrective maintenance downtime:
– Approximately 1-2 weeks per corrective maintenance7
– 2% offshore rig operational time lost8
7
Methodology
8
9
Components List 19
10
Serial Number Category of Component Components
1
BOP Stack
Annular Preventer
2 LMRP Connector (LMRPC)
3 Shear Ram
4 Pipe Ram
5 Test Ram
6 Wellhead Connector
7
Surface Control System
Hydraulic Power Unit (HPU)
8 Uninterruptible Power Supply (UPS)
9 MUX Cable Reel
10 Rigid Conduit & Hotline System
11 100 HP Pumps
12 Driller Control Panel
13 Rig Manager Control Panel
14 Central Control Console (CCC)
Components List 29
11
Serial Number Category of Component Components
15
Subsea Control System
Subsea Engineer Panel (SEP)
16 Subsea Electronic Module (SEM)
17 Subsea Electrical Power
18 LMRP Stack Accumulators
19 Power Distribution Panel
20 Choke/Kill System
Choke/Kill (CK) Lines
21 Choke/Kill (CK) Valves (8)
Assumptions
• Preventative maintenance is performed before each drilling job is started, and not during jobs
• Preventative maintenance downtime is negligible compared to the time between drilling jobs
• Overall reliability of the BOP system should be kept above a minimum threshold
• Constant failure rate
• It is possible to replace components at any time in between drilling jobs
• Maintenance fully restores component reliability to a value of one
• All components will either fail or work perfectly
• Components will be replaced on time by the beginning of the next drilling job
12
Pareto-Optimal Multi-Objective Optimization10
13
• minimize𝑥 𝐶𝑜𝑠𝑡 𝑥
• 𝑠. 𝑡. −𝑅𝑒𝑙𝑖𝑎𝑏𝑖𝑙𝑖𝑡𝑦 ≤ 𝜖
• 𝑔 𝑥 ≤ 0
• ℎ 𝑥 = 0
Results
14
Test Parameters
• BARON solvers
• 32-27 inch HP systems
• 3.2 GHz quad Xeon-E3 processors and
8GB RAM running Windows 7
• Maintenance Horizon: 1 year
– Mean computation time: 2.61 Hours
• Drilling jobs take 61 days
15
Maintenance Schedules
16
Sr No. Job 2 Job 3 Job 4 Job 5 Job 6 Job 7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
17
Rlow=0.600
18
Rlow=0.700
Sr No. Job 2 Job 3 Job 4 Job 5 Job 6 Job 7
1
2
3
4
5
6
7
8
9
10
11 1
12
13 1
14
15 1
16
17
18
19
20
21
19
Rlow=0.800
Sr No. Job 2 Job 3 Job 4 Job 5 Job 6 Job 7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
20
Rlow=0.900
Sr No. Job 2 Job 3 Job 4 Job 5 Job 6 Job 7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
21
Rlow=0.950
Sr No. Job 2 Job 3 Job 4 Job 5 Job 6 Job 7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Rlow=0.980
Sr No. Job 2 Job 3 Job 4 Job 5 Job 6 Job 7
1 1 1 1 1 1 1
2 1 1 1
3 1 1 1 1 1 1
4 1 1 1 1 1 1
5 1 1 1 1 1 1
6 1 1 1
7 1 1 1 1 1 1
8
9 1 1 1 1 1 1
10
11 1 1 1 1 1 1
12 1 1 1
13 1 1 1 1 1 1
14 1 1 1 1 1 1
15 1 1 1 1 1 1
16 1 1 1 1 1 1
17
18 1 1 1
19 1 1 1
20 1 1 1 1 1 1
21 1 1 1 1 1 1
Findings
23
Model Reduction
• From 𝑹𝒍𝒐𝒘 = 𝟎. 𝟔𝟎𝟎 to 𝑹𝒍𝒐𝒘 = 𝟎. 𝟗𝟗𝟎:
– UPS (8), rigid conduit & hotline system (10),
and subsea electrical power (17) components
were never maintained in this one-year period
– Except at 𝑹𝒍𝒐𝒘 = 𝟎. 𝟗𝟔𝟎, the LMRP stack
accumulators (18) were never maintained
24
Model Reduction
• From 𝑹𝒍𝒐𝒘 = 𝟎. 𝟔𝟎𝟎 to 𝑹𝒍𝒐𝒘 = 𝟎. 𝟗𝟗𝟎: – Choke/kill valves (21) were maintained for every
time step
• From 𝑹𝒍𝒐𝒘 = 𝟎. 𝟖𝟓𝟎 to 𝑹𝒍𝒐𝒘 = 𝟎. 𝟗𝟗𝟎: – Choke/kill lines (20) were maintained for every
time step
• From 𝑹𝒍𝒐𝒘 = 𝟎. 𝟗𝟐𝟎 to 𝑹𝒍𝒐𝒘 = 𝟎. 𝟗𝟗𝟎: – 100 HP pumps (11), rig manager control panel
(13), and CCC (14) were maintained for every time step
25
Trends
• Hydraulic components were maintained
more than electric components
• Although subsea control elements are the
most likely to cause incidents1, they are
not maintained as often because of the
high associated cost
26
Reliability vs Time
27
28
Rlow=0.600
29
Rlow=0.980
Cost vs Minimum Reliability
30
With a given budget, you can choose your
desired reliability
31
Incremental Cost for Risk-Efficient Decision
Making
32
Conclusions
• An optimization formulation has been developed for BOP maintenance scheduling that can: – Minimize overall maintenance cost
– Maintain reliability above a required threshold
– Generate maintenance schedules that prioritize components that are cost-efficient to maintain
– Allow decision-makers to determine the optimal maintenance schedule based on the cost and the minimum reliability.
– Allow decision-makers to determine the cost-effectiveness of changing minimum reliability.
33
Acknowledgements
• Nilesh Ade
• Dr. Mannan
• Dr. Koirala
• Dr. Liu
• Dr. Rogers
• Captain James Pettigrew
• Leon Schwartz
• Ms. Valerie Green
• Alanna Scheinerman
• All members of the MKOPSC
• All members of the OESI Advisory Committee
34
References
35
1) American Bureau of Shipping and ABSG Consulting Inc. , 2013. Blowout preventer reliability, availability
and maintainability analysis for Bureau of safety and environmental enforcement, s.l.: s.n.
2) J. Witthaus, "https://www.bizjournals.com/houston/morning_call/2016/07/bp-estimates-total-cost-of-
deepwater-horizon.html," BP estimates total cost of Deepwater Horizon disaster at $61.6B, 15 July 2015.
3) J. Vinnem and J. Erik, Offshore Risk Assessment, 3rd ed., Springer, 2014.
4) Arnold & Ipkin LLP, "Major Offshore Accidents of the 20th and 21st Century," 2017. [Online]. Available:
http://www.oilrigexplosionattorneys.com/Oil-Rig-Explosions/History-of-Offshore-Accidents.aspx.
[Accessed 23 July 2017].
5) R. Almeida, "BOP Blowout! $4.5 Billion Surge in Orders for 400-Ton Subsea Failsafe," gCaptain, 10
August 2012. [Online]. Available: http://gcaptain.com/blowout-4-5-billion-surge-orders/. [Accessed 2017
July 21].
6) SINTEF, SINTEF Offshore Blowout Database, 2013.
7) E. Draegebo, "Reliability Analysis of Blowout Preventer," Norwegian University of Science and
Technology, Department of Marine Technology, Trondheim, 2014.
8) Holand, "Reliability of Subsea BOP Systems for Deepwater Application & Fault tree analysis," SINTEF,
Trondheim, 1997.
9) American Bureau of Shipping and ABSG Consulting Inc., 2013. BLOWOUT PREVENTER (BOP)
FAILURE EVENT AND MAINTENANCE, INSPECTION AND TEST (MIT) DATA ANALYSIS FOR THE
BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT (BSEE), s.l.: Bureau of Safety and
Environmental Enforcement.
10) "What Is Multiobjective Optimization?," Mathworks, 2017. [Online]. Available:
https://www.mathworks.com/help/gads/what-is-multiobjective-optimization.html. [Accessed 20 July 2017].
Backup Slides
37
Objective Function
minimize𝑅 𝑐𝑜𝑠𝑡 = 𝑐𝑖,𝑡 ∗ 𝑥𝑖,𝑡 ∗ 𝑚𝑖
𝑛
𝑖=1
𝑇
𝑡=1
𝑐𝑖,𝑡: Cost of maintenance for component i at time t ($)
xi,t: Binary variable used to determine which, if any, component i is maintained at time t
i: Index of component
t: Time step (days)
𝑚𝑖: Number of parallel components of component i
38
Reliability at each Time Step
𝑅𝑖,𝑡 ≤ 𝑒− 𝜆𝑖𝑅𝑖,𝑡−1 + 𝑥𝑖,𝑡𝑀 ∀ 𝑖, 𝑡
𝑅𝑖,𝑡 ≥ 𝑒−𝜆𝑖𝑅𝑖,𝑡−1 − 𝑥𝑖,𝑡𝑀 ∀ 𝑖, 𝑡
𝑅𝑖,𝑡 ≤ 1 + 1 − 𝑥𝑖,𝑡 𝑀 ∀ 𝑖, 𝑡
𝑅𝑖,𝑡 ≥ 1 − 1 − 𝑥𝑖,𝑡 𝑀 ∀ 𝑖, 𝑡
39
𝑅𝑖,𝑡: Reliability of component, i, at time t
𝜆𝑖: Failure rate of component i xi,t: Binary variable used to determine which, if any,
component i is maintained at time t M: Big M formulation constant; M = 1
Reliability of Parallel Components
𝑅𝑝,𝑖,𝑡 = 1 − 1 − 𝑅𝑖,𝑡𝑚𝑖 ∀ 𝑖, 𝑡
𝑚𝑖: Number of parallel components of
component i
Rp,i,t: Reliability of parallel subsystem of
component i at time t
𝑅𝑖,𝑡: Reliability of component, i, at time t
40
Reliability of BOP Stack (Series)
𝑅𝑠,𝑡 = 𝑅𝑝,𝑖,𝑡
𝑛
𝑖=1
∀ 𝑡
Rp,i,t: Reliability of parallel subsystem of
component i at time t
Rs,t: Reliability of BOP system at time t
41
Reliability Constraint
𝑅𝑙𝑜𝑤 ≤ 𝑅𝑠,𝑡 ≤ 1 ∀ 𝑖, 𝑡
0 ≤ 𝑅𝑖,𝑡 ≤ 1 ∀ 𝑖, 𝑡
Rlow: Minimum reliability threshold of BOP
system (epsilon constraint)
𝑅𝑖,𝑡: Reliability of component, i, at time t
42