A safety barrier-based accident model for offshore drilling blowouts

Blowout is one of the most serious accidents in the offshore oil and gas industry. Accident records show that most of the offshore blowouts have occurred in the drilling phase. Efficient measures to prevent, mitigate, and control offshore drilling blowouts are important for the entire offshore oil and gas industry. This article proposes a new barrier-based accident model for drilling blowouts. The model is based on the three-level well control theory, and primary and secondary well control barriers and an extra well monitoring barrier are established between the reservoir and the blowout event. The three barriers are illustrated in a graphical model that is similar to the well-known Swiss cheese model. Five additional barriers are established to mitigate and control the blowout accident, and event tree analysis is used to analyze the possible consequence chains. Based on statistical data and literature reviews, failures of each barrier are presented. These failures can be used as guidance for offshore drilling operators to become aware of the vulnerabilities of the safety barrier system, and to assess the risk related to these barriers. The Macondo accident is used as a case study to show how the new model can be used to understand the development of the events leading to the accident. The model can also be used as an aid to prevent future blowouts or to stop the escalation of events.     

Associations between risk perception and safety

The relationship between perception of risk and involvement in accidents is receiving increasing attention in the offshore oil industry. A self-completion questionnaire survey was carried out among employees on twelve offshore oil installations in 1994.¹ The number of respondents were 1138. Employee evaluations of the status of safety and contingency measures were affected by physical working conditions, attitudes towards safety and accident prevention work as well as management commitment and involvement in safety promotion. These factors were also related to job stress, perceived risk and risk behaviour. There was a significant positive correlation between perceived risk and risk behaviour, but risk perception was not found to predict risk behaviour. Risk behaviour affected accidents as well as near-misses. The possibility that safety cannot be improved by changing individual risk perception is discussed.     

Revised fire consequence models for offshore quantitative risk assessment

Offshore oil and gas platforms are well known for their compact geometry, high degree of congestion, limited ventilation and difficult escape routes. A small mishap under such conditions can quickly escalate into a catastrophe. Among all the accidental process-related events occurring offshore, fire is the most frequently reported. It is, therefore, necessary to study the behavior of fires and quantity the hazards posed by them in order to complete a detailed quantitative risk assessment. While there are many consequence models available to predict fire hazards-varying from point source models to highly complex computational fluid dynamic models—only a few have been validated for the unique conditions found offshore.

In this paper, we have considered fire consequence modeling as a suite of sub-models such as individual fire models, radiation model, overpressure model, smoke and toxicity models and human impact models. This comprehensive suite of models was then revised by making the following modifications: (i) fire models: existing fire models have been reviewed and the ones most suitable for offshore conditions were selected; (ii) overpressure impact model: a model has been developed to quantify the overpressure effects from fires to investigate the possible damage from the hot combustion gases released in highly confined compartments; (iii) radiation model: instead of a point/area model, a multipoint grid-based model has been adopted for better modeling and analysis of radiation heat flux consequences. A comparison of the performance of the revised models with the ones used in a commercial software package for offshore risk assessment was also carried out and is discussed in the paper.     

Using lagging and leading indicators for the evaluation of occupational safety and health performance in industry

Improvement of occupational safety and health (OSH) management is closely related to the development of OSH performance measurement, which should include OSH outcomes (e.g., occupational accidents), OSH inputs (including working conditions) and OSH-related activities. The indicators used to measure the OSH outcomes are often called lagging indicators, and the indicators of inputs and OSH activities are leading indicators. A study was conducted in 60 companies in order to determine what kinds of indicators were used for OSH performance measurement by companies with different levels of OSH performance. The results reveal that the indicators most commonly used in all of the companies are those related to ensuring compliance with the statutory requirements. At the same time, the leading indicators are much more often adopted in companies with a higher performance level. These companies also much more often monitor on a regular basis the indicators adopted for the evaluation of their OSH performance.     

An Overview of the Nature of Hydrocarbon Jet Fire Hazards in the Oil and Gas Industry and a Simplified Approach to Assessing the Hazards

High pressure jet fires pose a serious hazard to offshore installations operated by the oil and gas industry as demonstrated by the Piper Alpha incident. Following the Piper Alpha incident a major initiative by the offshore oil and gas industry operators led to the production of Interim Guidance Notes which provided guidance to operators on how to assess jet fire hazards. However, many areas of uncertainty were identified where no data was available. Areas of particular concern identified in the Interim Guidance Notes were two-phase jet fires, the effect of confinement on jet fires and their behaviour with water deluge. Since that time a considerable body of experimental research has been undertaken. Based on this recent data, this paper reassesses jet fire hazards in an offshore environment and provides updated guidance on the hazards they pose, including tabulated data and simple calculation techniques for predicting jet fire hazards.     

Associations between sleep,risk and safety climate: A study of offshore personnel on the Norwegian continental shelf

The demands and constraints of the offshore working environment can have adverse effects on health, particularly the quality of sleep. Perceived risk and safety are significant psychological stress factors which may interfere with and deteriorate the sleep quality of offshore personnel. The present study explores the relationship between risk perception, safety climate and sleep quality. Data were collected under the auspices of the Petroleum Safety Authorities in Norway using a cross-sectional design. A total of 9601 offshore workers from 52 offshore installations on the Norwegian continental shelf participated in the study. Our findings indicate that both risk perception and safety climate are significantly related to sleep quality. The results of the present study suggest that risk perception and safety climate not only are important aspects of safety performance in the offshore industry, but also have an impact on sleep quality.     

Hydrocarbon releases on oil and gas production platforms: Release scenarios and safety barriers

The main objective of this paper is to present and discuss a set of scenarios that may lead to hydrocarbon releases on offshore oil and gas production platforms. Each release scenario is described by an initiating event (i.e., a deviation), the barrier functions introduced to prevent the initiating event from developing into a release, and how the barrier functions are implemented in terms of barrier systems. Both technical and human/operational safety barriers are considered. The initiating events are divided into five main categories: (1) human and operational errors, (2) technical failures, (3) process upsets, (4) external events or loads, and (5) latent failures from design. The release scenarios may be used as basis for analyses of: (a) the performance of safety barriers introduced to prevent hydrocarbon releases on specific platforms, (b) the platform specific hydrocarbon release frequencies in future quantitative risk analyses, (c) the effect on the total hydrocarbon release frequency of the safety barriers and risk reducing measures (or risk increasing changes).     

Risk perception by offshore workers on UK oil and gas platforms

This paper reports the first investigation of risk perception by workers on offshore oil and gas installations on the UK Continental Shelf, following changes in offshore safety legislation in the wake of the Piper Alpha disaster in 1988. The Offshore Safety Case regulations (Health and Safety Executive, 1992, A Guide to the Offshore Installations (Safety Case) Regulations) put the onus on the operator to identify the major hazards and to reduce the risks to As Low As is Reasonably Practicable (ALARP). The regulations specifically state that Quantitative Risk Assessments (QRA) must be used when preparing the Safety Case. However, people do not use QRA when making everyday judgements about risk; they make subjective judgements known as risk perceptions, which are influenced by a number of different factors. This study was designed to complement the extensive QRA calculations that have already been carried out in the development of Safety Cases. The aim was to measure subjective risk perception in offshore personnel and examine how this relates to the more objective risk data available, namely accident records and QRA calculations. This paper describes the Offshore Risk Perception Questionnaire developed to collect the data and reports on UK offshore workers' perceptions of the risks associated with major and minor hazards, work tasks and other activities aboard production platforms.     

Learning organisations for major hazards and the role of the regulator

A learning organisation is one that not only values and encourages learning from its own experiences, but also looks beyond itself for lessons, and avoids complacency. To be a learning organisation is a key part of the safety culture of any organisation involved with major hazard processes. It facilitates learning which can reduce the risk from major accident hazards. The paper provides a learning organisation toolkit which synthesises, from various literature sources, an understanding of what a learning organisation is and how to begin to develop one within an organisation. The paper illustrates how the regulator can be a learning organisation for major hazards, using the example of HSE's offshore fire, explosion and risk assessment team.     

基于BP神经网络的河南省火灾风险评价

采用火灾发生起数、死亡人数、受伤人数、直接经济损失、烧毁面积、受灾户数及人口火灾发生率7项指标构建河南省火灾风险评价综合体系,并用BP神经网络对该省份的18个地级市行政区的火灾风险进行评价,评价结果显示,该方法不但可以体现各地区的火灾风险相对水平,而且还可避免传统方法的主观性,具有较强的可行性和可靠性,对控制火灾风险、客观地反映各地区的消防工作现状具有一定的指导意义。     

Fire and explosion at mutual major hazard installations: review of a case history

In industry, it is common that there are independent but related major hazard installations which compliment each other. The link between the major hazard organizations is an interface between the installations. This interface is a critical area for the mutual major hazard installations. Examples of such organizations are chemical cargo ships and their terminal storage yard, the supply vessels and platforms, floating storage tanks at offshore areas and oil tankers, two offshore platforms tied together etc. This paper summarizes the major accident at M. T. Choon Hong III Ship and Tiram Kimia Sdn. Bhd. (TKSB), and also discusses the causes which led to this major accident. It was found that the lack of integrity is the main cause behind the escalation of the fire and explosion at the Choon Hong III Ship and the TKSB. It was noted that the disaster which involved mutual major hazard installation was preceded by two incubation periods.     

Developing safety indicators for preventing offshore oil and gas deepwater drilling blowouts

An important question with respect to the Macondo blowout is whether the accident is a symptom of systemic safety problems in the deepwater drilling industry. An answer to such a question is hard to obtain unless the risk level of the oil and gas (O&G) industry is monitored and evaluated over time. This article presents information and indicators from the Risk Level Project (RNNP) in the Norwegian O&G industry related to safety climate, barriers and undesired incidents, and discusses the relevance for deepwater drilling. The main focus of the major hazard indicators in RNNP is on production installations, whereas only a limited number of incident indicators and barrier indicators are related to mobile drilling units. The number of kicks is an important indicator for the whole drilling industry, because it is an incident with the potential to cause a blowout. Currently, the development and monitoring of safety indicators in the O&G industry seems to be limited to a short list of “accepted” indicators, but there is a need for more extensive monitoring and understanding. This article suggests areas of extensions of the indicators in RNNP for drilling based on experience from the Macondo blowout. The areas are related to schedule and cost, well planning, operational aspects, well incidents, operators’ well response, operational aspects and status of safety critical equipment. Indicators are suggested for some of the areas. For other areas, more research is needed to identify the indicators and their relevance and validity.     

Shift schedules on North Sea oil/gas installations: A systematic review of their impact on performance,safety and health

Continuous production processes on North Sea installations necessitate extended work schedules; 2-week offshore tours (alternating with shore breaks), 12 h shifts and rapid day/night shift changes are inherent features of offshore work. These intensive rosters, worked in a demanding physical and psychosocial environment, are potential sources of fatigue and impaired performance among offshore personnel. This article focuses on offshore working time arrangements, and presents a systematic review of studies which examine offshore day/night shift patterns in relation to operational safety and individual health risks. Of the 53 studies retrieved, 24 met the review criteria.Field study findings are generally consistent in showing that sleep, alertness and performance are relatively stable across day-shift tours; initial night shifts are adversely affected by circadian disruption, but full physiological and psychological adaptation occurs within 5–6 days; re-adaptation to day shifts is slower, and varies widely across individuals; the offshore environment is conducive to night-shift adaptation, but interventions to facilitate re-adaptation have proved only modestly effective. Analyses of survey data and accident/sickness records identify offshore night work as a risk factor for impaired sleep, health problems, and injuries, but little is known about the long-term health effects of different offshore shift rotations.In conclusion, research methodology and findings, and working time issues of current concern to the offshore oil/gas industry, are discussed. Aspects of offshore work schedules that have been not been widely studied (e.g. overtime, irregular work patterns) are also highlighted, and research areas that would merit further attention are noted.     

Risk assessment in the offshore industry

This paper describes the implementation and use of risk assessment in the offshore industry in relation to safety aspects — safety to people's life and health, as well as environment and property. Although risk assessments may be based on both qualitative and quantitative methods, the main focus here will be on quantitative risk assessments (QRA). The development of offshore QRA has been lead by a mutual influence and interaction between the regulatory authorities for the UK and Norwegian sectors of the North Sea as well as the oil companies operating here. The experience from this area has been the main basis during the writing of this paper.     

Safety climate and hydrocarbon leaks: An empirical contribution to the leading-lagging indicator discussion

Hydrocarbon (HC) leaks are important initiating events for major accidents in the oil and gas industry. This study explores the extent to which a safety climate indicator from a survey on working conditions undertaken in an oil and gas company (n = 2188) can be used as a leading and/or lagging indicator in relation to HC leaks on 28 offshore installations. It was found that more negative safety climate scores were associated with increasing numbers of HC leaks over a 12-month period following the survey. The safety climate indicator explained more of the variance in HC leaks than technical indicators. HC leaks in the 12-month period preceding the survey did also correlate significantly with the safety climate indicator. More HC leaks during this period were associated with worse scores on the safety climate indicator. Thus, the results support that the safety climate measure could serve as leading and lagging indicator for HC leaks. The results and their possible implications are discussed.     

Evaluation of the Risk OMT model for maintenance work on major offshore process equipment

Operational safety is receiving more and more attention in the Norwegian offshore industry. Almost two thirds of all leaks on offshore installations in the period 2001–2005, according to the Risk Level Project by the Petroleum Safety Authority in Norway, resulted from manual operations and interventions, as well as shut-down and start-up. The intention with the Risk OMT (risk modelling – integration of organisational, human and technical factors) program has been to develop more representative models for calculation of leak frequencies as a function of the volume of manual operations and interventions. In the Risk OMT project a generic risk model has been developed and is adapted to use for specific failure scenarios. The model considers the operational barriers in event trees and fault trees, as well as risk influencing factors that determine the basic event probabilities in the fault trees. The full model, which applies Bayesian belief networks, is presented more thoroughly in a separate paper. This paper presents the evaluation of the model. The model has been evaluated through some case studies, and one important aspect is the evaluation of the importance of each risk influencing factor. In addition some risk-reducing measures have been proposed, and the paper presents how the effect of these measures has been evaluated by using the model. Finally, possible applications and recommendations for further work are discussed.     

Acoustic analysis of blast waves produced by rapid phase transition of LNG released on water

Massive offshore and onshore storage of fuel have led the international community to raise questions about the hazards on the surrounding installations and people. Among the possible accidental scenarios when cryogenic gas as liquefied natural gas (LNG) is spilled on water at a very fast rate, the phenomenon of rapid phase transition (RPT) may occur: large amounts of energy are released during phase transition which can generate explosions. The related consequences should be added to the possible consequences of fire in terms of flash fire, fireball, pool fire, and vapour cloud explosion for confined and congested geometry surrounding the release point.In this paper, the analysis of RPT of LNG has been studied from the point of view of blast wave production, through ab initio acoustic analysis for monopole source. Maximum overpressures, as calculated at the source point and along the blast pathway are compared with results of large scale experiments. Safety distances are given for the sake of comparison with threshold distances reported in the open literature.     

Quantitative risk analysis of fire and explosion on the top-side LNG-liquefaction process of LNG-FPSO

Since the massive use and production of fuel oil and natural gas, the excavating locations of buried energy-carrying material are moving further away from onshore, eventually requiring floating production systems like floating production, storage and offloading (FPSO). Among those platforms, LNG-FPSO will play a leading role to satisfy the global demands for the natural gas in near future; the LNG-FPSO system is designed to deal with all the LNG processing activities, near the gas field. However, even a single disaster on an offshore plant would put the whole business into danger. In this research, the risk of fire and explosion in the LNG-FPSO is assessed by quantitative risk analysis, including frequency and consequence analyses, focusing on the LNG liquefaction process (DMR cycle). The consequence analysis is modeled by using a popular analysis tool PHAST. To assess the risk of this system, 5 release model scenarios are set for the LNG and refrigerant leakages from valves, selected as the most probable scenarios causing fire and explosion. From the results, it is found that the introduction of additional protection methods to reduce the effect of fire and explosion under ALARP criteria is not required, and two cases of the selection of independent protection layers are recommended to meet the SIL level of failure rate for safer design and operation in the offshore environment.     

Advanced multi-perspective computer simulation as a tool for reliable consequence analysis

Major accidents involving hazardous materials are a crucial issue for the chemical and process industries. Many accidental events taken place in the past showed that dangerous substances may pose a severe threat for people and property. Aiming at loss prevention, a series of actions have been instituted through international regulations concerning hazardous installations safety preparedness. These actions involve efficient land-use planning, safety studies execution, as well as emergency response planning drawing up. A key factor for the substantial consideration of the above is the effective prediction of possible accident forms and their consequences, for the estimation of which, a number of empirical models have been developed so far. However, (semi-)empirical models present certain deficiencies and obey to certain assumptions, thus leading to results of reduced accuracy. Another approach that could be used for this purpose and it is discussed in this work, is the utilization of advanced computational fluid dynamics (CFD) techniques in certain accident forms modeling. In particular, composite CFD-based models were developed for the simulation of several characteristic accident forms involving isothermal and non-isothermal heavy gas dispersion, confined and unconfined explosion in environment of complex geometry, as well as flammable cloud fire. The simulation cases were referred to real-scale trials allowing us to conclude about the validity of the quantitative results. Comparisons of the computational predictions with the experimental observations showed that obtained results were in good agreement with the experimental ones, whereas the evaluation of statistical performance measures proved the simulations to be statistically valid.     

Combustion products toxicity risk assessment in an offshore installation

Products of a hydrocarbon fire accident have both chronic and acute health effects. They cause respiratory issues to lung cancer. While fire is the most frequent phenomenon among the offshore accidents, predicting the contaminants’ concentration and their behavior are key issues. Safety measures design, such as ventilation and emergency routes based only on predicted contaminants’ concentration seems not to be the best approach. In a combustion process, various harmful substances are produced and their concentration cannot be added. The time duration that any individual spends in different locations of an offshore installation also varies significantly. A risk-based approach considers the duration a person is exposed to contaminants at various locations and also evaluates the hazardous impacts. A risk-based approach has also an additivity characteristic which helps to assess overall risk.Through the current study, an approach is proposed to be used for risk assessment of combustion products dispersion phenomenon in a confined or semi-confined facility. Considering CO, NO₂ and CH₄ as the contaminants of concern, the dispersion of the substances over the layout of the facility after a LNG fire is modeled. Considering different exposure times for three major parts of the facility including the processing area, office area and the accommodation module, the risk contours of CO, NO₂ and CH₄ over the entire facility are developed. The additivity characteristic of the risk-based approach was used to calculate the overall risk. The proposed approach helps to better design safety measures to minimize the impacts and effective emergency evacuation planning.