ECONOMIC FEASIBILITY STUDY OF SEVERAL UTILIZATION ALTERNATIVES FOR A STRANDED OFFSHORE GAS RESERVOIR

Floating Liquefied Natural Gas (FLNG) has been on the rise in recent years to meet growing energy demand, worldwide. As energy consumption and exploitation of onshore unconventional gas reservoirs continue to grow while gas price remains almost steady, FLNG can potentially become the winning card for operators in conventional offshore gas fields through integration of upstream and midstream processes on the spot. This thesis compares project economics of a FLNG utilization to those of onshore LNG plant, and Gas-to-Wire (GTW) processes. We primarily conducted sensitivity analysis and tornado charts to evaluate importance of various uncertain parameters associated with FLNG construction and operation. Costs for the hypothetical FLNG vessel is taken from Shell’s Prelude FLNG; while pipeline, LNG plant, and gas-to-wire costs were obtained from typical industry standards. A typical hyperbolic decline curve model is applied to model depletion flow regime of production life after 5 to 10 years constant rate plateau time. Several factors are included in the sensitivity analysis: LNG price, interest rate, initial production rate, and condensate-to-gas ratio (CGR), plateau time, distance from onshore, electricity price, natural gas price and percentage share of overnight capital cost of building a power plant to convert gas to electricity. The factors are used to gauge their effects on the net present value (NPV) of each scenario and are ranked based on their sensitivity on a tornado chart. The analysis suggest that initial production rate has the strongest effect on NPV, followed by discount rate, LNG price, CGR, and the distance from onshore when the reservoir is dry gas. Our analysis showed that, the longer the distance from onshore, the more attractive the FLNG alternative becomes. However, when gas price is low, and a subsidy from the Nigerian government can be obtained, GTW becomes attractive. This economic feasibility study will be helpful for future considerations to use FLNG to make previously considered stranded offshore gas reservoir economically viable. This will certainly play a key role in the future of natural gas industry and energy market, especially in West Africa

Gas explosion analysis of safety gap effect on the innovating FLNG vessel with a cylindrical platform

© 2016 Elsevier LtdAfter investigating gas dispersion on a cylindrical Floating Liquefied Natural Gas (FLNG) platform (Li et al, 2016), this second article focuses on assessment of gas explosion by using Computational Fluid Dynamics (CFD). Gas explosion simulations are carried out to evaluate the explosion overpressure mitigating effect of safety gap. The Data-dump technique, which is an effective tool in resetting turbulence length scale in gas explosion overpressure calculation, is applied to ensure simulation accuracy for the congestion scenario with safety gap. Two sets of different safety gaps are designed to investigate the safety gap on the cylindrical FLNG platform, the overall results indicate that the safety gap is effective in reducing overpressure in two adjacent congestions. However, for the explosion scenario where the flame is propagating through several safety gaps to the far field congestion, the safety gap mitigates overpressure only in certain explosion protecting targets. Two series of artificial configurations are modeled to further investigate the explosion scenarios with more than two safety gaps in one direction. It is concluded that the optimal safety gap design in overpressure mitigation for the cylindrical FLNG platform is to balance the safety gap distance ratio in the congested regions

Modelling an integrated impact of fire, explosion and combustion products during transitional events caused by an accidental release of LNG

In a complex processing facility, there is likelihood of occurrence of cascading scenarios, i.e. hydrocarbon release, fire, explosion and dispersion of combustion products. The consequence of such scenarios, when combined, can be more severe than their individual impact. Hence, actual impact can be only representedby integration of above mentioned events. A novel methodology is proposed to model an evolving accident scenario during an incidental release of LNG in a complex processing facility. The methodology is applied to a case study considering transitional scenarios namely spill, pool formation and evaporation of LNG, dispersion of natural gas, and the consequent fire, explosion and dispersion of combustion products using Computational Fluid Dynamics (CFD). Probit functions are employed to analyze individual impacts and a ranking method is used to combine various impacts to identify risk during the transitional events.The results confirmed that in a large and complex facility, an LNG fire can transit to a vapor cloud explosion ifthe necessary conditions are met, i.e.the flammable range, ignition source with enough energy and congestion/confinement level. Therefore, the integrated consequences are more severe than those associated with the individual ones, and need to be properly assessed. This study would provide an insight for an effective analysis of potential consequences of an LNG spill in any LNG processing facility and it can be useful for the safety measured design of process facilities

Study on the Flow and Heat Transfer Characteristics in the Tube Side of Spiral-Wound Heat Exchanger

In this article, the characteristics of hydrocarbons condensation flow and heat transfe in tube-side of spiral wound heat exchanger under static and sloshing conditions were numerically investigated based on the verified model. It is shown that at static conditions, as the vapor quality increases, the heat transfer coefficient first increases and then decreases, whereas the frictional pressure drop always increases. The pure hydrocarbon shows better flow and heat transfer performances than hydrocarbon mixture. Moreover, sloshing motions could bring about both drag reduction and heat transfer enhancement. These results are helpful to understand condensation flow in a spiral pipe. Keywords: hydrocarbons, condensation, spiral pipe, sloshing motio

Assessment of flexible operation in an LNG plant

Process industries are becoming increasingly reliant on electrical power for reasons of efficiency and sustainability. A large industrial site typically has its own power management system to distribute electricity to the process and to manage electrical contingencies such as partial loss of supply. Recent work has illustrated more flexible alternatives to load shedding whereby an industrial process plant can continue to operate at a lower level making use of available electrical power. This paper presents a way for achieving such flexibility in a Liquefied Natural Gas (LNG) plant. It analyzes the consequences for production of varying the consumed power, and assesses the maximum flexibility within the feasible operating envelope of the process. The study has been conducted by modeling and simulation of an LNG plant using the Linde process with three refrigeration cycles. The results also show the relationships between electrical power consumption and production in terms of production rate and product characteristics. They also show that the vapour-liquid equilibrium plays a crucial role in establishing the operating points and setting the boundaries in which the process has to work. Thus, through the assessment and simulation of an LNG plant, this work demonstrates that flexible operation has benefits over alternatives. It achieves more operating points and therefore adds more flexibility

Analisa Risiko Kebakaran Proses Gas Liquefaction

Potensi gas bumi yang dimiliki Indonesia berdasarkan status tahun 2008 mencapai 170 Triliun Spesific Cubic Feet (TSCF) dan lokasi jauh dari daratan, sehingga untuk mengamankan aset tersebut pemerintah Indonesia merencanakan sebuah bangunan lepas pantai yang mampu melakukan exploitasi dengan aman dan ekonomis, maka Floating Liquefied Natural Gas (FLNG) merupakan sebuah pilihan tepat. Namun instalasi tersebut merupakan sebuah teknologi instalasi lepas pantai yang sangat kompleks, sehingga dibutuhkan sebuah analisa yang tepat dalam memelihara keberlangsungan proses pengelolaan gas tersebut dengan aman. Terlebih pada proses liquefaction unit yang kondisi gasnya masih sangat rentan untuk terjadinya kebakaran yang ditimbulkan oleh gas release dan jenis pendingin yang digunakan adalah termasuk jenis chemical yang mudah terbakar. Untuk itu perlu dilakukan analisa risiko terhadap sistem tersebut. Metode penilaian risiko dilakukan berdasarkan peraturan Risk Assessment Applications for The Marine and Offshore OIL and Gas Industries. Dimana hazard identifikasi dilakukan dengan menggunakan HAZard Operability (HAZOP), analisa frekuensi gas release dengan menggunakan Fault Tree Analysis (FTA). Dari nilai tersebut ditentukan frekuensi terjadinya kemungkinan akibat dari gas release seperti Jet Fire, Flash Fire, Gas Explosion dan Gas Dispersion dengan menggunakan Event Tree Analisys (ETA). Selanjutnya dilakukan analisa Konsekuensi dengan menggunakan software ALOHA. Berdasarkan hasil analisis frequency dan consequences, maka tingkat risiko direpresentasikan dengan menggunakan f-N curve yang mengacu pada standard UK Offshore 1991 diperoleh hasil bahwa potensi yang ditimbulkan oleh jenis risiko jet fire untuk hole 50 mm berada pada kondisi (As Low As Reasonably Practicable) ALARP, Dimana kondisi ini masih berada pada kondisi risiko yang aman, namun bisa juga dilakukan mitigasi, salah satu langkah mitigasi yang dilakukan yaitu menambah komponen pengaman untuk mencegah terjadinya overpressure pada pipa serta menambah alat keselamatan para pekerja. Sedangkan untuk diameter kebocoran 100 mm dan 200 mm berada pada kondisi Acceptable artinya risiko berada pada kondisi dapat diterima. Untuk konsekuensi gas explosion kemungkinan terjadinya sangat kecil dengan nilai frekuensinya <10-6. Dan konsekuensi gas dispersion tidak dapat mengakibatkan efek beracun pada manusia karena gas yang terilis berada dibawah 50,000 ppm. =================================================================================================== The potential amount of natural gas owned by Indonesia, based on the data in 2008, reached 170 Trillion Specific Cubic Feet (TSCF) and it is located far away from the mainland. To secure this asset, the Government of Indonesia planned to build an offshore facility to be able to exploit it safely and economically, which is why the Floating Liquefied Natural Gas (FLNG) became an ideal option. However, FLNG is an offshore installation with a complex technology, so a proper analysis to maintain the continuity of the process gas safety management is a necessity. This becomes very important especially in the liquefaction unit process that is very vulnerable to fire due to gas release and inflammable type of chemical refrigerant. Therefore, risk assessment on the system must be conducted. The method of risk assessment conducted complied with the Risk Assessment Applications for The Marine and Offshore Oil and Gas Industries, in which hazard identification was carried out using Hazard Operability (HAZOP) and the analysis of gas release frequency was performed using Fault Tree Analysis (FTA). The results of these analyses were used to run Event Tree Analysis (ETA) to find out the possible frequency of gas release related cases, such as Jet Fire, Flash Fire, Gas Explosion, and Gas Dispersion. After that, consequences analysis was conducted using ALOHA software. Frequency and consequences analyses showed a level of risk indicated with f-N curve, referring to UK Offshore 1991. The results revealed that the chance for a jet fire to take place with a 50 mm hole is considered ALARP (As Low As Reasonably Practicable), which means that this is a safe condition but mitigations can still be carried out. Some of the possible mitigations that can be done are to add safety components to prevent overpressure in the pipe and provide additional safety equipment for workers. Furthermore, a leak with a diameter of 100 mm and 200 mm is considered acceptable, which means that the risk is on an acceptable level. The possibility of gas explosion to take place is also very low with a frequency value <10-6 and gas dispersion will not have a hazardous effect on human since the released gas is under 50,000 ppm

Methods for determining the optimal arrangement of water deluge systems on offshore installations

Offshore installations are prone to fire and/or explosion accidents. Fires have particularly serious consequences due to their high temperatures and heat flux, which affect humans, structures and environments alike. Due to the hydrocarbon explosions caused by delayed ignition following gas dispersion, fires can be the result of immediate ignition after gas release. Accordingly, it can be difficult to decrease their frequency, which is an element of risk (risk=frequency×consequence), using an active protection system (APS) such as gas detectors capable of shutting down the operation. Thus, it is more efficient to reduce the consequence using a passive protection system (PSS) such as water spray. It is important to decide the number and location of water deluge systems, thus the aim of this study is to introduce a new procedure for optimising the locations of water deluge systems using the water deluge location index (WLI) proposed herein. The locations of water deluge systems are thus optimised based on the results of credible fire scenarios using a three-dimensional computational fluid dynamics (CFD) tool. The effects of water spray and the effectiveness of the WLI are investigated in comparison with uniformly distributed sprays

Mooring Lines Reliability Analysis Case Study: Fso Abherka,

Floating Storage and Offloading (FSO) demands good designs. One of the design is FSO’s mooring lines. The mooring lines of the FSO would face various environmental conditions, so that they are required to have good reliability. FSO Abherka, installed in the Madura stratit, has dimensions of LOA 242.90 m, LPP 232 m, Breadth 41.6 m, Height 19.7 m, Draft 12,894 m, and a deadweight of 85829 tons. The strait has a water depth of 100 m with contour variations of ± 2 m. Each four cluster of mooring lines of FSO Abherka has three mooring ropes. This study analyzed the strength of mooring lines in intact and damaged conditions using DNV software Genie and DNV HydroD. This study models a hydrodynamic FSO. This study also measured the reliability of the mooring lines from 2 cases: 1 intact and one damage from the most dangerous conditions. This study used the mean Value First Order Second Moment method to find the reliability of these mooring lines. Based on the reliability calculation set by DNV according to DNV-OS E301, the mooring lines design meet the established reliability criteri

Greater Role of Natural Gas in the Energy Transition

The pathway to a low carbon future primarily depends on a nation\u27s availability of energy resources, economic growth, government policies, pattern of land USAge, energy diplomacy, affordability and a gradual energy transition towards cleaner fuels. In such transitions, an old energy economy shifts to a newer energy economy by switching from old fossil fuel generations to more efficient technologies, thereby increasing the energy productivity; developing alternative fuels, such as renewables and more importantly, producing and using natural gas more responsibly. DOI: 10.5281/zenodo.346012