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Risk analysis
C H A P T E R
13 Risk analysis O U T L I N E Introduction
453
Project cost optimization CapEx vs OpEx 453 Historic frequency of blockages based on remediation 453
Modeling dynamic behavior
454
Integration of various precipitation phenomena
454
Impact on overall planning
454
Introduction Several operator companies are migrating their project development approach from flow assurance issues prevention to issue risk probability management. This approach allows to defer cost for the facility development while possibly increasing the operating cost and difficulty.
Project cost optimization CapEx vs OpEx Projects tend to be CapEx-lean and OpEx heavy due to the uncertainty in reservoir performance. If reservoir is a strong producer and the produced commodity market is expected to be strong, then additional facilities may be developed.
Historic frequency of blockages based on remediation The risk-based approach to flow assurance relies on historic frequency of blockages to forecast the future probability of a blockage. Historic blockage frequencies and trends were presented in Chapter 5.
Handbook of Multiphase Flow Assurance https://doi.org/10.1016/B978-0-12-813062-9.00013-0
453
© 2019 Elsevier Inc. All rights reserved.
454
13. Risk analysis
Modeling dynamic behavior Probabilities of individual flow assurance issues should be tabulated along with the impact of such an event. Individual risks should be integrated in a dynamic field development model to evaluate a range of probabilistic scenarios for reaching the target profitability performance for the field. Time-dependent events such as aquifer water breakthrough or injection water breakthrough should be reflected by the increased risk to project performance. After the project starts, with time, more understanding of the relative weights and consequences for individual flow assurance risks becomes available. Risk based model should be kept updated to both optimize the risk evaluation for the existing field and to serve as probability basis for the future fields.
Integration of various precipitation phenomena All flow assurance and production chemistry issues should be evaluated simultaneously. The likelihood of one issue may increase the probability of a different issue. An example from a West African subsea tieback operation shows that a wax deposition risk was not managed and wax was allowed to deposit and remain in the pipe as it was not causing a significant hydraulic resistance to flow. A hydrate plug then formed, became solid. During pressure changes attempting to resolve the blockage, the hydrate plug became mobile and scraped wax off the pipe wall like a pig, compacting it into a secondary blockage. While hydrate could be dissociated by depressurization, the paraffin blockage could not. This caused a significant downtime to gradually dissolve the paraffin blockage with a solvent. A similar example from USA deepwater shows a flowline where asphaltene was allowed to deposit, which provided local restrictions in the pipe cross-section and promoted hydrate accumulation and blockage.
Impact on overall planning The combined field development plan should be prepared with input from and interaction with flow assurance and production chemistry specialists, as well as corrosion engineers. A systematic approach to risk analysis of the individual flow assurance issues and their integration in a field development model can be used to support investment decisions.
13 Risk analysis O U T L I N E Introduction
453
Project cost optimization CapEx vs OpEx 453 Historic frequency of blockages based on remediation 453
Modeling dynamic behavior
454
Integration of various precipitation phenomena
454
Impact on overall planning
454
Introduction Several operator companies are migrating their project development approach from flow assurance issues prevention to issue risk probability management. This approach allows to defer cost for the facility development while possibly increasing the operating cost and difficulty.
Project cost optimization CapEx vs OpEx Projects tend to be CapEx-lean and OpEx heavy due to the uncertainty in reservoir performance. If reservoir is a strong producer and the produced commodity market is expected to be strong, then additional facilities may be developed.
Historic frequency of blockages based on remediation The risk-based approach to flow assurance relies on historic frequency of blockages to forecast the future probability of a blockage. Historic blockage frequencies and trends were presented in Chapter 5.
Handbook of Multiphase Flow Assurance https://doi.org/10.1016/B978-0-12-813062-9.00013-0
453
© 2019 Elsevier Inc. All rights reserved.
454
13. Risk analysis
Modeling dynamic behavior Probabilities of individual flow assurance issues should be tabulated along with the impact of such an event. Individual risks should be integrated in a dynamic field development model to evaluate a range of probabilistic scenarios for reaching the target profitability performance for the field. Time-dependent events such as aquifer water breakthrough or injection water breakthrough should be reflected by the increased risk to project performance. After the project starts, with time, more understanding of the relative weights and consequences for individual flow assurance risks becomes available. Risk based model should be kept updated to both optimize the risk evaluation for the existing field and to serve as probability basis for the future fields.
Integration of various precipitation phenomena All flow assurance and production chemistry issues should be evaluated simultaneously. The likelihood of one issue may increase the probability of a different issue. An example from a West African subsea tieback operation shows that a wax deposition risk was not managed and wax was allowed to deposit and remain in the pipe as it was not causing a significant hydraulic resistance to flow. A hydrate plug then formed, became solid. During pressure changes attempting to resolve the blockage, the hydrate plug became mobile and scraped wax off the pipe wall like a pig, compacting it into a secondary blockage. While hydrate could be dissociated by depressurization, the paraffin blockage could not. This caused a significant downtime to gradually dissolve the paraffin blockage with a solvent. A similar example from USA deepwater shows a flowline where asphaltene was allowed to deposit, which provided local restrictions in the pipe cross-section and promoted hydrate accumulation and blockage.
Impact on overall planning The combined field development plan should be prepared with input from and interaction with flow assurance and production chemistry specialists, as well as corrosion engineers. A systematic approach to risk analysis of the individual flow assurance issues and their integration in a field development model can be used to support investment decisions.