Toxic Gas Release in Onshore Oil Platforms - Case Study Example

Note: Please just send a message if you need anything. Thanks! Toxic Gas Release (H2S) in Onshore Oil Platforms Table of Contents Contents Contents 2 1. Introduction In reality, controlling of toxic gas release hazards means preventing serious loss of containment on the one hand and dealing with the consequences of such release on the other (Mannan & Lees, p.18). However, in order to prevent serious loss of containment and handle the consequences of the subsequent disaster, one must be knowledgeable of the risk beforehand and plan ahead. Risk assessment such as QRA can help oil exploration and production companies plan ahead and are prepared for the consequences of their operation. These include assessing the risk posed to personnel as well as the community that may be affected by accidental gas release. Understanding and analysing various gas release scenarios and take them into account in the design and construction of the facility. The following sections discuss risk assessment strategies that can help reduced risk posed by onshore oil platform’s operation. These include the level and value of risk calculated through FAR, PLL, IR, and F-N, assessment of three different accidents involving oil and gas releases, and the potential use of QRA to ensure safe and environmentally responsible operation of onshore oil platforms. 2. Aim and Objectives The aim of this report is to analyse and understand how gas release scenarios are used to design and build safe processing facilities and prevent serious gas releases such as H2S or Hydrogen Sulfide, a colourless but poisonous and flammable gas. The report also aims to contribute additional information that can help decision-makers make relevant and effective decisions to ensure safe design of facilities, The objective on the other hand is to assess the role of credible gas release scenarios in facilitating a near estimate of the overall risk in relation to IR or Individual Risk and PLL or Potential Loss of Life, and facility design. 3. FAR, PLL, IR, and F-N In life safety, FAR or Fatal Accident Rate is commonly used to describe the level of risk at its value is the estimated number of fatalities per million. FAR is associated with different personnel activities such as PLL which is the estimated number of fatalities per year. On the other hand, AIR or the Average Individual Risk is the average probability of dying in an accident. Therefore, assuming n is the number of personnel exposed to a certain risk and t are the hours per year then the formula for FAR is FAR = [PLL/nt] 108 while AIR is AIR = PLL/n (Aven, 2008, p.25). These formula are often use in risk analysis in order to have a basis for choosing an alternative approach. For instance, risk analysis that will be carried out in a process where considerable modifications are being done (i.e. adding new production equipment) will often assume increase level risk for personnel that will be exposed to such activities. Similarly, adding new equipment or repair of particular part of a gas and oil production facility means additional risk as such installation or work can lead to leaks and subsequent fire and explosion (Grimvall, 2010, p.190). Therefore, the likely decision is whether to evaluated existing safety measures or install additional safety measures to protect personnel or reduce fatalities in case of leaks (p.190). According to Chavas (2004), one of the most important factors contributing to the existence and prevalence of risk is the inability to measure and control the risk (p.6). This is because risk measurement and control requires detailed knowledge of the interaction between people and their environment. For instance, conducting risk analysis in an oil and gas facility requires not only knowledge of accidental events and their consequences and statistics of failures and accidents relevant to the facility but detailed knowledge of the facility itself. For the purpose of risk analysis according to Taylor (1994), it is always important to determine if the existing protective measures of certain facility is reasonable or what modifications should be made in order to reduce the risk level. Moreover, this risk level should be in the level of general acceptability and evaluated against the immediate consequences (i.e. heat radiation, explosions, poisoning, and others) and long-terms effects to people and the environment (p.22). 4. Assessment of Bhopal Pesticide Plant Accident In December 1984, Union Carbide India Limited in Bhopal released toxic gases from its methyl isocyanate storage tank that injured hundreds of people and killed thousands of those living in Jayaprakash, a shanty town outside the plant. Investigation of the accident suggests that the temperature and pressure inside the methyl isocynate or MIC tank rose because it was contaminated by 2000 pounds of water. Since the tank was designed with safety valves to prevent over pressurization, it opened and rapidly released toxic gases into the atmosphere. The investigating body found safety standards and maintenance procedures of the plant inadequate. For instance, examination of the MIC safety systems reveal that the refrigeration system to cool the tank was shut down, temperature and pressure gauges were faulty, temperature alarm is not working correctly, the tank exceeds it capacity by 30%, and the toxic gas community alarm was triggered an hour late (Joseph et al, 2005, p.538). Result of independent study concerning the Bhopal accidents suggest management’s inattention to both safety and design, poor risk management, inability of public authorities to monitor and control private corporations and their facilities (Kasperson & Kasperson, 2005, p.5). According to Mannan et al, (2005), the Bhopal accident occurred because safety in chemical processing was never an issue before Bhopal despite several incidents like the release of cyclohexane in Flixborough in June 1974, the 1976 Seveso, Italy incident where dioxin was released, and the 1984 gas release incident involving LPG BLEVE in Mexico City (p.219). Bhopal changed how government view chemical processing and increased public environmental consciousness against toxic substances (Willey et al, 2005, p.366). 5. Assessment of BP Oil Leak in Gulf of Mexico The disastrous BP or British Petroleum oil spill occurred in 2010 as a result of an explosion from the Deepwater Horizon oil drilling rig in the Gulf of Mexico. Eleven people died from the accident while fifteen were severely injured. The accident happened when the blowout prevented failed while workers of Transocean, a contractor of BP, were temporarily closing the well. The next days, another explosion occurred that caused the Deepwater Horizon to finally sink into the ocean along with the riser pipe attached to the defective blowout preventer. Consequently, three oil leaks were discovered 5000 feet below the ocean that was estimated to be leaking around 1000 barrels of oil per day. BP attempted to install a shutoff valve but failed and the oil continually drifts toward the coast of Alabama and Florida (Hiles, 2010, p.624). In terms of safety, drilling for oil according to the National Commission (2011) on the BP Deepwater Horizon spill is always dangerous considering the heavy machineries and volatile hydrocarbons being extracted at high pressures. Moreover, oil drilling in the Gulf of Mexico alone historically claimed 60 human lives and 1,550 injured as a result of 948 fires and explosions (p.3). Investigation of BP’s safety practices suggests that it had no acceptable risk assessment and management plan. For instance, the 582 page Gulf of Mexico Plan was created by BP with the assumption that an accidental oil spill will only affect ten miles of the ocean. Aside from having no realistic prediction, BP had no plan and tools to deal with large-scale oil spill despite having poor maintenance and cutting corners practices (Hiles, 2010, p.627). 6. The Ohio Waster Treatment H2S Gas Release In December 2002, hydrogen sulphide (H2S) was accidentally released due to incorrect vessel for waste treatment. Investigation of the gas release suggest that the facility has no formal operating procedures for waste water treatment and relying on the knowledge and long experience of its workers. Consequently, the operator made a procedural mistake and instead of transferring the batch back to the treatment where it could mix and ventilated properly, he mixed the contents of the clarifier with pressurized air that accidently produce H2S as the air mixing did not totally dissolved the Na2S in the clarifier and evenly distribute the acidic PAC. Moreover, investigators found no written hazard instructions and procedures in case such event occurs (US Chemical Safety and Hazard Investigation Board, 2003, p.9). Aside from lack of formal training, the operator for the WWT area only relied on his own knowledge of waste treatment protocols and ignorant of the possible chemical reactions when he failed to mix Na2S and PAC effectively. Moreover, investigators found no hazard communication and evacuation procedure in place as everybody in the workplace assume that someone knowledgeable will inform them about the danger and facilitate an evacuation. Although there was no casualty other than the maintenance worker who entered the WWT area during the leak, report shows that about 2 pounds of H2S was released while the newly installed H2S detector failed to alarm because it has bad sensor, uncalibrated, and not properly maintained for around 3 months (US Chemical Safety and Hazard Investigation Board, 2003,p.11). Using fault tree analysis, investigators found that contributing factors to gas release include treatment of chemical in a vessel not designed for the purpose as clarifiers are commonly not equipped with agitator and scrubbers that minimizes the chances of toxic gas release, management is unaware of law prohibiting addition of Na2S, no clear safety policy and procedures, poor equipment and facility maintenance practices, and lack of effective management systems (US Chemical Safety and Hazard Investigation Board, 2003, p.12). 7. QRA in Onshore Oil and Gas Platforms A stepped process, QRA or Quantitative Risk Assessment have been instrumental to a number of risk related decisions as the US regulation of carcinogens, OSHA’s (Occupational Safety and Health Administration) lowering the benzene standards by 9 ppm in 1977, and others. According to Bate (1997) QRA possess scientific reliability and useful for setting priorities and public expectation on the numbers lives that will be save if QRA result is use to create regulations (p.84). The US National Research Council is also very keen in using QRA in risk management program as evidenced by their high regard to the 1996 review of Tooele Chemical Agent Disposal Facility where the findings of the QRA matches the interim findings in the systematization report (Bley & Eremenko, 2003, p.127). According to Bley & Eremenko (2003), QRA identifies systems, components, and activities that are risky and relevant to the business of the facility such disposal of highly toxic chemicals (p.127). The use of QRA methodology is popular among offshore facilities where it involves risky activities including exploration drilling, construction, sub-sea working, high pressures, and potential leaks. However, according to Turney & Pitblado (1996), although they share similar activities, extracting hydrocarbon fluids, and process equipment, QRA in offshore facilities is different from QRA on onshore oil platforms in a number of ways. For instance, the physical area of offshore platforms is small and congested; there is strong possibility of losing personnel as they work in the ocean, and wider focus on protective systems and emergency evacuation of personnel (p.99). Recent QRA employed by Germanischer Lloyd or GL, an assurance and consulting company for maritime and energy industries, for a Middle East onshore oil company include determining the consequences and risk associated with a number of hazards such as explosions, jet fires, smoke, pool fires, and flash fires. This QRA according to GL (2008), take into account the initial release conditions, mixture thermodynamics, transient release rates, gas cloud density, emissions, radiant heat, and others (p.4). GL’s scenario evaluation technique has been through long experience with onshore plants that include “event trees” for common major accidents scenarios and “fault tree” analysis in order to determine likely failure frequencies in the absence of historical data for such event. For instance, in order to calculate the consequences, GL take into account a wide range of release positions such as direction of pipe work, predominant direction flow of gas within the pipe, wind speed, delayed ignition times, effect of flash fire and running pool fire, and others in pipeline rupture scenarios (GL, 2008, p.5). Figure 1- GL's Overview of Risk Management Methodology Similarly, JP Kenny Limited’s QRA of the onshore section of the Corrib Field being development by Shell Ireland and Allseas Construction Contractors S.A. take into account the risk associated with operation of the pipelines. These include risk associated with the pig receiver, hazards from failing umbilical and water outfall pipeline loss containment. Generally, the purpose of QRA in this project is to determine the individual risk and potential loss of life of the public that may be affected by the onshore section of the Corrib gas pipeline. Moreover, it is being done to demonstrate that residual risks associated with the operation are reduced to acceptable level. Similar to GL, JF Kenny’s consequence analysis is typical for onshore pipelines as include hazardous gas release, release rate scenarios, jet fire and flash fire scenarios, and others (JF Kenny, 2005, p.13). QRA in the context of onshore oil and gas exploration does measure risks associated with activities in both production and processing of chemicals. It identifies almost all possible risks situations and quantifies them as events of consequences, frequency of occurrence, and compares them established and accepted criteria. It can be viewed as a means to maximize safety, a tool that can be use to develop safety models, an aid to decision making and insurance purposes, and a risk reducer at lower cost. 8. The Role of Gas Release Scenario in Facility Safety Design A negative scenario that can prevent the attainment of safety goals is a risk scenario (de Lemos et al, 2007, p.398). However, development of risk scenario and corresponding safety design and regulation requires historical knowledge or prior experience. According to Levy (2008), it is difficult to predict a risk scenario that never happened before (p.35). Similarly, fail-safe design is almost always the first consideration but it is not possible due undetectable flaws and fatigue life of materials used in construction (Kutz, 2002, p.684). Failure modes in gas release scenarios are divided into several events that were identified from both previous experience and large scale test. According to Misra (2008), each gas release scenarios were found to have an initiating event and subsequent failure events that resulted to fire and explosion and fatalities. Similarly, the frequency of occurrence is based on previous experiences showing the initiating events that led to the consequences. For instance, initiating events such failure of mechanisms that led to catastrophic hardware failures that eventually trigger instant release of gas in the presence of an ignition source is identified from previous gas releases accidents (p.712). Creating a gas release scenario based on the Bhopal catastrophe will yield several important risk information such as the danger of mixing water and MIC, cooling system failure, inaccurate gauges, failure of warning alarms, failure of safety devices, inadequately designed flare, overcapacity, failure of mitigation procedures such as water curtain, and many others (Joseph et al, 2005, p.538). Similarly, creating a risk scenario based on BP Oil Spill and Ohio H2S gas release will yield a number of potential risk such as poor maintenance and cutting corners practices, use of defective materials, underestimation of risks and their consequences, unpreparedness in the face of disaster, inadequate or absence of safety procedures, faulty alarm systems, ignorance and lack of training, hazard communication failure, and others. Companies with onshore oil processing facilities can take advantage of QRA along with realistic gas release scenario to ensure safe facility design. Assessment should be conducted in accordance with existing laws particularly those that are concerned with environmental protection and risk assessment. Since most oil companies use pipelines to transfer their products and operate in a plant, the QRA must cover all possible risk and consequences relevant to pipeline and onshore oil processing operation. Following methodologies learned earlier with GL, the steps in the risk analysis must incorporate scenario selection followed frequency and consequence assessment, risk assessment, comparison with criteria, and formulation of risk reduction approaches. Note that calculated risk should be compared to government safety criteria of the country where the onshore platform is operating. For the purpose of this report, the maximum off-site IR (the impact on individuals outside the plant) should not exceed 10 in a million per year or 1 x 10-5 per year. Similarly, supporting toxic gas release scenario may be taken previous accidents and safety systems software containing databases of risk and potential hazards in the industry such HAZOP and HAZID which were designed using actual experiences in hydrocarbon plant design and operations (GL, 2008, p.6). Scenarios that may be considered in onshore oil platforms is not limited to immediate facility but include scenarios outside the plant such ruptures and punctures of pipeline between offshore and onshore sites. Ruptures and punctures of valves stations above and below the ground, failure of process and storage vessels, small to large condensate releases, and others (see Table below for details). Table 1- Possible Scenarios in Onshore Oil Platforms (GL, 2000) Scenarios that may be considered in Onshore Oil Platforms Area Scenario # Scenario name Description Pipeline 1 Pipeline extending beyond the plant Ruptures and punctures of pipeline resulting to release of toxic gases 2 Pipeline within the plant Same as above 3 Pipeline above and below ground Rupture of pipes and valves resulting to contamination and release of chemicals Inlet 4 Inlet pipeline and slug-catcher unit Rupture of pipes resulting to release of toxic gas from the slug-catcher 5 Condensate Stabilization Failure of process vessels resulting to release of condensate Processing 6 Oil processing Failure of process vessels resulting to releases of hydrocarbon and gas 7 Liquefaction Failure of process vessels resulting to release of refrigerant and other chemicals Storage 8 Hydrocarbon storage Failure of storage vessels resulting to release of hydrocarbon materials 9 Product storage Failure of storage vessels resulting to release of oil and other chemicals Transport 10 Ships, trucks, and trains Failure of safety valves resulting to release of oil and gas 9. Conclusion Assessing the role of credible gas release scenario is essential in estimating the impact of such risk in the individual and potential loss of life in the affected community. The Bhopal gas release, the BP oil spill, and the Ohio H2S gas release are good example of these scenarios as they can be used to identify risk scenarios in similar facilities including onshore oil platforms. As evidenced by the widespread use of QRA, gas release scenarios and other risk related scenarios are taken into account in design and construction of safe processing facilities. It is impacting decisions as evidence by several legislation associated with the impact oil and gas industry in human health and environment. Gas release scenario and QRA in general is applicable to anticipated H2S and other gas release related risk in onshore oil platforms as the result will be likely compliant with international accepted risk and safety criteria as well as reducing risk levels in almost all activities of the plant. 10. 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