High Integrity Pressure Protection System Research Articles

Hazard evaluation and safety assessment for subsea HIPPS

AbstractThe safety practice of depressurization of pipelines by flare system in the hydrocarbon industry is not sufficient for pipelines in the subsea production process. There are many challenges in the subsea production process due to multiphase fluid flow. Failure of a process to arrive at its safe state could result in fatality, significant property damage, and can lead to a disastrous environment. The safe state of a process is identified through the consequence of hazard and risk assessments at critical modes of operations. A well‐designed safety instrumented function (SIF) can prevent escalation of minor malfunction into an accident. The prime objective of this work is to obtain the required safety integrity level (SIL) for subsea High Integrity Pressure Protection System (HIPPS). Based on hazard assessment (HAZOP) and risk assessment (LOPA), SIL for SIF is recommended, and finally through reliability calculations, the SIL for subsea HIPPS is determined.

A fault diagnosis method for the HIPPS of FPSO unit based on dynamic Bayesian network

The high integrity pressure protection system (HIPPS) on the Floating Production Storage and Offloading (FPSO) unit is essential for handling various emergencies. However, if the location of the fault cannot be accurately identified, proper measures may not be taken to isolate the hazard. This paper presents a fault diagnosis method for HIPPS on FPSO units based on Dynamic Bayesian network (DBN). The method considers the influence of sensor and system equipment degradation on the diagnosis results and avoids the problem of overdiagnosis in static diagnosis networks. Six fault diagnosis cases of the system are analyzed and discussed to verify the accuracy and effectiveness of the proposed method. By changing the failure rate of the faulty component, it is determined that the posterior probability of the faulty component increases with the increase of the failure rate at the same time.

Reliability and availability evaluation of subsea high integrity pressure protection system using stochastic Petri net

In this paper, a safety evaluation method of subsea High Integrity Pressure Protection System (HIPPS) based on a generalized stochastic Petri net model is proposed. Different test methods were used to detect different types of failures and to analyze the reliability of HIPPS components under the influence of common cause failures and incomplete repair. The reliability curve of a diagnostic system consisting of a transmitter system and a logic system under the influence of uncertainty over time is analyzed. The safety of HIPPS with diverse test methods were quantitatively analyzed. The results show a significant improvement in the performance of the system after testing and maintenance. Both partial-stroke testing and increased partial-stroke test coverage can be used to increase the HIPPS performance compared to traditional methods. The analysis of the Partial stroke test (PST) strategy can afford a academic basis for the selection of PST frequency and Functional test (FT) interval in practical engineering.

Modeling for evaluation of safety instrumented systems with heterogeneous components

A novel methodology for evaluation of safety instrumented systems (SISs) with heterogeneous components based on multi-stage dynamic Bayesian networks (MDBNs) is proposed. The unified evaluation model for M-out-of-N architectures based on MDBNs is constructed. An automatic modeling method of conditional probability tables for time-slice and inter-slice transitions is established. Average probability of failure on demand (PFDavg) and probability of failing safety (PFS) of the structure can be calculated by the established model. A method for calculating the life-cycle cost of SISs is presented by using the results of system evaluation and specific cost details. A high-integrity pressure protection system (HIPPS) is adopted to demonstrate the application of the proposed approach. A MDBNs-based evaluation and cost analysis software of heterogeneous redundant structure is developed by using MATLAB graphical user interface. The analysis of system evaluation results and life-cycle cost can help the designer determine the configuration of the heterogeneous redundant structure.

High integrity pressure protection system (HIPPS) usage justification from safety and reliability point of views

High integrity pressure protection system (HIPPS) usage justification from safety and reliability point of views

Reliability and availability modeling of Subsea Autonomous High Integrity Pressure Protection System with partial stroke test by Dynamic Bayesian

Subsea Autonomous High Integrity Pressure Protection System is used in the subsea production process to lower the pressure level of downstream equipment and pipelines and to protect low-pressure pipelines and equipment. Once failure occurs, it will cause serious environmental damage and huge economic losses. In this article, a method of Dynamic Bayesian networks is proposed based on different failure types detected by different test methods. The reliability and availability of HIPPS with different detection methods were analyzed quantitatively. The results show that the performance of the system is improved significantly after inspection and maintenance. Compared with traditional methods, the performance of HIPPS is improved after the partial stroke test is introduced. Through sensitivity analysis, it is found that failure rates have a greater impact on the reliability of HIPPS valves. Increasing partial stroke test coverage can improve HIPPS performance. To improve the reliability of HIPPS, it is necessary to improve the reliability of the execution unit, especially the HIPPS valves. The analysis of the PST strategy can provide a theoretical basis for selecting the frequency of partial stroke test and functional test interval in actual projects.

Transient Wellbore-Pressure-Buildup Correlation Helps Engineers To Ensure HIPPS Safe Operation

Summary The objective of this study is to develop a correlation for transient wellbore-pressure buildup and relate it to the high-integrity pressure-protection system (HIPPS) response time in multiphase flow. The developed correlation gives an accurate estimate of the pressure buildup with time under shut-in conditions. It provides guidelines to set the HIPPS activation pressure considering different reservoir and wellbore parameters to ensure the safety and timely response of HIPPS. The correlation was developed by performing transient simulations to calculate the wellbore-pressure-buildup time under shut-in conditions accounting for different reservoir and wellbore parameters. The input data were gathered from three oil fields with various fluid properties, reservoir pressures, productivity indices (PIs), depths, and shut-in wellhead pressures (SIWHPs). Before feeding the data to the dynamic flow simulator, the reservoir data were tuned to match the well-flow conditions. After completing the transient simulation for every well, the pressure-buildup data as a function of time were collected and used as input to develop a correlation using the nonlinear-regression method. The results of this study show that the most influential parameters on the pressure-buildup behaviors are fluid compressibility, PI, flowing wellhead pressure (FWHP), and well measured depth (MD). In addition, we observed that there is a strong relationship between the fluid compressibility at FWHP condition and the time it takes to pressurize the wellbore to maximum pressure. The higher the fluid compressibility, the longer it takes the system to pressurize. The newly developed correlation provides a guideline for setting the HIPPS activation pressure and ensuring the wells’ safe operation.

Reliability modeling of subsea SISs partial testing subject to delayed restoration

Subsea oil and gas production has always involved the challenging task of determining the overall reliability of safeguarding systems, such as safety instrumented systems (SISs). Partial testing and delayed restoration of SISs are the main issues in operation and maintenance activities. This paper proposes a novel reliability-modeling methodology for subsea SISs subject to partial testing and delayed restoration. The proposed methodology incorporates an increasing failure rate in conjunction with dangerous undetected failures for the final elements. Approximation formulas for evaluating the average probability of failure on demand are derived for SISs in the low-demand operating mode. In addition, the effects of degradation are modeled by following Weibull rules in different subsequent partial testing intervals. In contrast to previous works, the present research accounts for delayed restoration after detecting failures and also considers the repair time for different scenarios. The proposed formulas are compared with the existing ones for partial verification. A case study on the shutdown valves of a subsea high-integrity pressure protection system is presented to illustrate the feasibility of the proposed methodology. It is also proven that the proposed approximation offers a robust opportunity for testing strategy optimization and performance improvement of SISs.

Reliability assessment for final elements of SISs with time dependent failures

Reliability assessment for safety-instrumented systems (SISs) plays a vital role in improving the design of SISs. Traditional methods for SIS reliability assessment that assume constant failure rates are, however, not realistic for many final elements of SISs, e.g. electro-mechanical and hydraulic/mechanical actuators that are subject to degradation. This paper presents an approach for reliability assessment of SIS final elements with time dependent failure rates. Different operational issues, such as partial and full testing, are investigated for their effects on reliability of SISs. Approximation formulas for evaluation of average probability of failure on demand (PFDavg) involving degradation are developed within different subsequent proof testing intervals, and Weibull distributions are adopted to model the degradation processes of the final elements. The corresponding numerical results of PFDavg from the set of the derived formulations are validated by Petri nets models that are developed for different scenarios. Shutdown valves installed as part of a high integrity pressure protection system are analyzed as the case, to illustrate the feasibility of the proposed approach, and also demonstrate that the approximation can provide possibilities for testing strategies design and optimization.

Dealing with uncertainty in effect analysis of test strategies on safety instrumented system performance

In this paper, we have attempted to show the effect of test strategies on the performance of safety instrumented system (SIS) in a fuzzy parameter environment. Two types of test strategies are considered: simultaneous and staggered tests. As a relevant parameters of SIS, common cause failure factor and diagnostic coverage ( $$DC$$ ) rate are modeled by triangular fuzzy numbers and are injected into the fuzzy Markov model to calculate the fuzzy PFD of SIS. Sensitivity analysis is carried out to show the effect of fuzzy beta and $$DC$$ variation on average fuzzy PFD of the SIS. An application case focused on a high integrity pressure protection system is carried out.

A three-stage scenario based operational performance test approaches for production capacity enhancement: Case study on the 5th refinery of South Pars Gas Complex in Iran

In this work, the possibility of capacity enhancement in the South Pars Gas Complex of Iran has been studied. Mass balance is studied and data validation and reconciliation have been carried out in 5th refinery of South Pars Gas Complex in order to achieve the reliable data of the plant. Then the possibility of capacity increase has been studied, taking into account the important parameters such as alteration of the plant pressure profile. Calculation of the key parameters for different equipment at higher feed rate, specified the unit of operations which may have trouble during the capacity enhancement. The performance of export gas compressors, dehydration unit and High-Integrity Pressure Protection System (HIPPS) has been anticipated to be the obstacle of this project according to the results of design basis review. In order to increase the feed rate the operation at constant inlet pressure is considered while the final stage pressure decreases as it is safe procedure for the plant. Then performance test has been carried out to monitor the changes in the plant. Three methodologies were designed and evaluated for implementing the performance test, and the stepwise procedure has been carried out successfully. During the performance test, the feed rate has been increased in three consecutive steps by 4.5%, 3% and 2.5% respectively. The operation of key equipment such as turbo expanders, exports and refrigerant compressors, dehydration beds, columns and filters, have been examined by taking samples from inlet–outlet streams such as feed gas, acid gas, lean and rich amine, LPG product. Following the step wised feed rate increase, the performance test was operationally successful and the production capacity of sweet gas in South Pars has been increased about 10%.

Handling Uncertainties in Fault Tree Analysis by a Hybrid Probabilistic–Possibilistic Framework

Fault tree analysis is a method largely used in probabilistic risk assessment. Uncertainties should be properly handled in fault tree analyses to support a robust decision making. While many sources of uncertainties are considered, dependence uncertainties are not much explored. Such uncertainties can be labeled as ‘epistemic’ because of the way dependence is modeled. In practice, despite probability theory, alternative mathematical structures, including possibility theory and fuzzy set theory, for the representation of epistemic uncertainty can be used. In this article, a fuzzy β factor is considered to represent the failure dependence uncertainties among basic events. The relationship between β factor and system failure probability is analyzed to support the use of a hybrid probabilistic–possibilistic approach. As a result, a complete hybrid probabilistic–possibilistic framework is constructed. A case study of a high integrity pressure protection system is discussed. The results show that the proposed method provides decision makers a more accurate understanding of the system under analysis when failure dependencies are involved. Copyright © 2015 John Wiley & Sons, Ltd.

HIPPS-Based No-Burst Design of Flowlines and Risers

Summary A methodology is proposed for design of subsea flowlines and risers coupled with a subsea high-integrity pressure protection system (HIPPS) for fields with high shut-in tubing pressure (SITP). The proposed approach uses a design pressure that is lower than the SITP while maintaining a high reliability against burst failure. This approach enables an inherently safer design and ensures that the system integrity is not compromised in the unlikely event that HIPPS valves fail to close upon demand. The proposed design methodology is supported by a combination of analytical and experimental results. Further, an example is provided for demonstration purposes.

Integrating RAMS engineering and management with the safety life cycle of IEC 61508

This article outlines a new approach to reliability, availability, maintainability, and safety (RAMS) engineering and management. The new approach covers all phases of the new product development process and is aimed at producers of complex products like safety instrumented systems (SIS). The article discusses main RAMS requirements to a SIS and presents these requirements in a holistic perspective. The approach is based on a new life cycle model for product development and integrates this model into the safety life cycle of IEC 61508. A high integrity pressure protection system (HIPPS) for an offshore oil and gas application is used to illustrate the approach.

Subsea HIPPS: A Way To Develop High-Pressure Subsea Fields

Summary One of the challenges for the development of high-pressure oil and gas prospects in ultradeep water is the high capital-expenditure (CAPEX) cost of subsea flowlines and risers. Installing a high integrity pressure protection system (HIPPS) in the subsea system allows the flowline to be designed to just above well flowing pressure instead of well shut-in pressure. On the basis of flow simulations, pipeline design, and economic analysis, this paper demonstrates that installing subsea HIPPS results in the following: Lower installed cost of flowlines and risers. Early payback with incrementally higher flow of oil and gas. Secondary benefits including higher flowing wellhead and flowline temperatures. Another important benefit of using subsea HIPPS is that the weight of the risers hanging off at the host facility can be reduced substantially. Otherwise, heavy-walled risers may restrict the tie-in of the deepwater prospect to host facilities. With pressure decline over time, the thick-walled flowlines become overkill and tend to restrict the well flow rate. With subsea HIPPS, the larger flow area in the subsea flowlines will allow the field to be abandoned at a lower reservoir pressure. This means that that the total recoverable reserves from the field can be increased. The major finding of this paper is that for high-pressure reservoirs in ultradeep water, installing HIPPS subsea accelerates cash flow and increases the project net present value. These benefits will be illustrated on the basis of the analysis of a deepwater field-development design case.

High Integrity Pressure Protection Systems For Production Applications

Abstract Through the use of a High Integrity Pressure Protection System (HIPPS) the flare capacity of a wellhead platform can be reduced to the flowrate required for depressurisation. The HIPPS may also be used to reduce the flare capacity of a process plant. By the use of HIPPS, the discharge of hydrocarbons or carbon dioxide due to venting/flaring is reduced. This paper describes the development of HIPPS for the Sleipner B-platform offshore Norway. A 20" multiphase pipeline is protected against overpressure by two 20" quick acting shut down valves (QSV) installed in series, instead of pressure safety valves. The valves have been qualified for operation in wellstream at a shut-in pressure of 336 bar, and have a closing time of 2 seconds. Each of the QSVs has independent, fail safe instrumentation cirquits. A parallel train of QSVs has been installed due to the testing requirements. The estimated saving using HIPPS on SLB was $ 25 mill. The paper also discuss existing and new applications of the HIPPS.