blowout preventer (bop) maintenance schedule for...

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

denis@tamu.edu

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].

36

Questions?

Comments? denis@tamu.edu

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