THE SNØHVIT DESIGN REFLECTS A SUSTAINABLE ENVIRONMENTAL STRATEGY LE PROJET GNL SNØHVIT TRADUIT UNE STRATEGIE ENVIRONNEMENTALE DURABLE

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1 THE SNØHVIT DESIN REFLECTS A SUSTAINABLE ENVIRONMENTAL STRATEY LE PROJET NL SNØHVIT TRADUIT UNE STRATEIE ENVIRONNEMENTALE DURABLE Roy Scott Heiersted Sigbjørn Lillesund Svein Nordhasli eir A Owren Kirsti Tangvik Statoil ASA, Norway ABSTRACT The Snøhvit LN Development Project is a milestone project, for Statoil and for the Norwegian Continental Shelf, as the first natural gas development project in the Norwegian part of the Barents Sea. This area is housing one of the most important fishing grounds in the world, thus it is zero tolerance for untreated effluents to the sea. Strict requirements also apply for effluents to air, due to restrictive regulations from the Norwegian authorities. In the development of the Snøhvit project, Statoil corporate philosophy on HSE issues is ranked very high when setting criteria for technology selection. The project is utilizing international guidelines, referred as Best Available Techniques, in the approach to selecting technical concepts. This is in compliance with the Statoil HSE philosophy, for developing a sustainable oil and gas industry. In order to further improve the Snøhvit project environmental profile, and contribute to the governmental requirements according to the Kyoto Protocol, the carbon dioxide removed from the feed gas will be recompressed, dried and injected via a pipeline to an offshore formation for disposal. This concept utilizes experience and technology developed by Statoil for the Sleipner field in the North Sea, where carbon dioxide is removed from the gas, dried and injected into a huge reservoir, before sales gas export to Europe. RESUME Le projet NL Snøhvit est une première, tant pour Statoil, que pour le plateau continental norvégien, étant le premier projet de développement de gaz naturel dans la partie norvégienne de la Mer de Barents. Cette région héberge une des plus importantes pêcheries du monde; signifiant une «tolérance zéro» pour le rejet en mer d effluents non traités. Des conditions requises strictes, s appliquent aussi aux effluents rejetés dans l atmosphère, à cause des strictes règlementations imposées par les autorités norvégiennes. Dans le développement du projet Snøhvit, Statoil a placé très haut ses critères de sélection de technologie dans le domaine sécurité et environnement. Le projet se sert des directives internationales, connues sous le nom de «Best Available Techniques» dans la démarche pour sélectionner les concepts techniques. Ceci est conforme à l approche PS5-4.1

2 sécurité et environnement de Statoil dans le cadre du développement durable de l industrie pétrolière et gazière. Pour améliorer le profil environnemental du projet Snøhvit et pour contribuer aux conditions requises par la règlementation, conformément au protocole de Kyoto, le CO 2 extrait du gaz d alimentation sera recomprimé, séché et injecté à travers un gazoduc dans une formation en mer. Ce concept utilise l expérience et la technologie développées par Statoil pour le champ de Sleipner en Mer du Nord, où, après extraction et réinjection du CO 2 dans une formation réservoir, le gaz est exporté vers l Europe Continentale. SNØHVIT LN PROJECT The Snøhvit fields located in the Barents Sea The Snøhvit area is part of the Norwegian Continental Shelf at 71 o North in the Tromsøflaket West province of the Barents Sea. The gas fields are located kilometres offshore in meters water depth. The gas and condensate resources were discovered in the early 1980s, and are located in three different fields, Askeladd, Albatross and Snøhvit. All three fields is part of the Snøhvit LN Development Project. The resources in place are in excess of 300 billion cubic meters of gas and additionally 20 million cubic meters of condensate. The Snøhvit license partners made their final commitment to commercialize the gas and condensate reserves of the Snøhvit area in September The Norwegian Parliament approved the plan for development and operation of the Snøhvit area in March PS5-4.2

3 2002. The Snøhvit LN chain will provide the first LN base load production in Europe. Commitments in gas sales agreements are based on firm deliveries from October 1, Statoil is operator of the Snøhvit LN Development Project, having the overall responsibility from reservoir to marketing, securing focus and consistency in the entire value chain. The Snøhvit partners are Statoil ASA, PETORO, Total Norge AS, Norsk Hydro Production AS, RWE-DEA Norge AS, Amerada Hess Norge AS, Svenska Petroleum Exploration and az de France Norge AS. Hammerfest LN Plant The Snøhvit LN Project is a milestone project, for Statoil and for the Norwegian Continental Shelf, as the first natural gas development project in the Norwegian part of the Barents Sea. There is a very high environmental attention on the impacts regarding emissions to air and sea. However, there is no oil production and only minimal amount of formation water produced from the reservoirs. The development is gas production only, which makes the environmental challenge more easily to control. The Snøhvit fields are commercialized through a grass roots LN development. The LN plant will be built in the vicinity of the city of Hammerfest, on the northernmost coastline of Norway. To maximize the net present value for the owners, the project aims at cost efficiency in all aspects of the project development, being in the fore-front of technology and execution methods to obtain the lowest unit production costs. Compared to conventional PS5-4.3

4 LN plant executions, the project has changed the philosophy from on-site, stick-built solutions to yard prefabrication, placing focus on maximum work executed in fabrication yards. Among the most fundamental project decisions is to install the pre-treatment and liquefaction processes and the power and heat system of the LN plant in a compact layout on a purpose built barge, thereby minimising construction work on site. The process barge is pre-fabricated in Spain and transported to site on the Norwegian coast of the Barents Sea in the summer of The prefabricated process, including the barge as foundation, weighs totally tons in transportation. Regarding the optimal capacity taking all relevant risks into consideration, the Snøhvit project decided an LN production capacity of 4.3 million tons per annum (mtpa) in the single train plant. The capacity of the chain is based on a field production of 6.9 Sm3/year, resulting in three products (LN, LP and condensate) totaling 6.0 Sm3/year. The result of the project s environmental strategy is that the overall energy need in the offshore transportation and the onshore processing and liquefaction, up to products shipment, are covered by a fuel consumption of less than 6% of the feed flow. REULATORY REQUIREMENTS IN NORWAY The European Union (EU) sets common rules on permitting for industrial installations in IPPC (Integrated Prevention Pollution Control) directive of 1996.The IPPC directive is about minimizing of pollution from various point sources. In Norway, similar strict requirements apply for effluents both to air and water, due to restrictive regulations from the Norwegian authorities. In the process of obtaining the permission to develop and operate the LN chain, several formal concessions are required for the Snøhvit LN Development Project, both before and after the governmental approval. Upfront of the approval of the Plan for Development and Operations (PDO) by the Norwegian Parliament, the comprehensive Environmental Impact Assessment (EIA) report must be approved in a public hearing. The report describes the project, the consequences of the project on the environment and alternative development concepts. After the PDO approval, the project has applied for the permit of discharges to sea, emissions to air, waste handling and noise, which is issued by the Norwegian Pollution Control Authority (SFT). The legal basis for SFT is the Pollution Control Act, which establishes the principle that pollution is prohibited unless special permission has been granted, either by law, by regulation or as an individual permit. The evaluation and decision criteria are the BAT definitions and the IPPC directive and national regulations (the othenburg Protocol i.e. European Agreement on Reduction of acidification, eutrophication and ground level ozone, 1999). The othenburg Protocol commits Norway to reduce the NOx-emission by 29% in 2010, in relation to emissions in Since the project includes gas fueled power production this system should be approved by Norwegian Water Resources and Energy Directorate (NVE). NVE is subordinated to the Ministry of Petroleum and Energy, and is responsible for the administration of the nation's water end energy resources. PS5-4.4

5 Together with the approval of the overall thermal efficiency and the emissions, the selection of the power and heat system concept itself is subject to formal approval by the named authorities. In 2003, NVE has granted the Snøhvit project the concession to install and operate 230 MW of electric power production and 210 MW of recovered thermal heat in the first gas fueled power plant of this magnitude in Norway. STATOIL CORPORATE ENVIRONMENTAL STRATEY Statoil s corporate objectives in health, safety and the environment (HSE) are to accomplish the exploration, construction and operation with zero harm to people or the environment, and with zero accidents or losses. The zero harm to the environment is defined as: Conserving of biodiversity Limiting emissions and discharges Limiting land use Restore and clean used areas when activity is completed Conserve landscape and cultural heritage. Statoil s corporate targets and minimum standards are: Achieve, by the year 2010, an annual reduction of 1.5 million tons of CO2 equivalent on equity basis. Results will be calculated by assessing the amount that would have been released if no special measures had been taken, and by comparing that figure against actual performance. Eliminate use and discharge of hazardous substances (substances or groups of substances that are toxic, persistent and liable to bio-accumulate). Chemicals containing hazardous substances may only be used if technical or safety performance is jeopardized, still the environmental risk should be minimized. Best Available Techniques shall generally be applied. Operating units/projects shall document their specific choice of BAT. uidelines for selection of BAT may be found in NORSOK S-003, World Bank guidelines (onshore and offshore) and EU IPPC BREF document. Permanent production flaring i.e. continuous flaring for gas disposal is not accepted. BAT for the Snøhvit LN Plant The definition of Best Available Techniques contains an element of judgement related to costs involved. Therefore, in the Snøhvit LN Project, systems involving emission have been compared and selected based on economical robustness in life cycle cost comparisons involving potential quota purchases in the future. The most significant BAT contributions in the design of Snøhvit LN chain are: Statoil have taken a pro-active role in the CO2 sequestration. Snøhvit is the first land based industry development that uses technology for CO2 sequestration involving offshore reservoirs. The CO2 re-injection is tons per year. The Snøhvit reservoir area comprises a subsea field development and the gas wells are connected to shore by a multiphase pipeline. No harmful effluent PS5-4.5

6 releases or emissions occur from the offshore system. All well streams are routed to the land based facility for processing. All effluents and emissions from the reservoir production are treated, handled and released in a controlled manner at the LN plant. First priority in BAT is maximizing the thermal efficiency of the gas processing and liquefaction to reduce demand for fuel. For the LN process in particular, the selection of the Mixed Fluid Cascade process (MFC ) represents the state-of-theart in thermodynamic design of the industry. With the selection of the gas treatment processes, involving amdea for the CO2 removal, the overall heat demand is optimized for minimum emissions to air and sea. The gas turbine selection primarily addresses high mechanical (electrical) efficiency, as this is the constraint relative to fuel gas consumption. At the same time the waste heat from the flue gas provides all process heat demands, due to the heat balance, without installing additional gas fired furnace capacity. To produce the total need for power and heat in the plant, aero-derivative gas turbines is combined with flue gas heat recovery units based on hot-oil. This provides a high performance utility system, which is equally efficient to gas- and steam turbine based combined heat and power systems. Electric motors, provided with variable speed features, driving the refrigeration compressors, are part of BAT and contribute to optimal operations modes related to capacity balancing. Dry low NOx burners for the gas turbines are applied to guarantee an overall emission level of 25 ppm while maintaining high combustion efficiency. Further, the project will prepare implementation of future commercially viable technology, which would reduce emissions. When the end-flash process of LN liquefaction is not relevant, fuel gas to the selected aero-derivative gas turbines is taken from the gas feed to the LN facility instead of taking processed gas or LN as fuel. This saves an increase to plant design capacity by six per cent of gas processing and cooling duty demand. The Snøhvit plant, as the first in the industry, will fully process return gases from loading of LN and LP carriers at the facility. Snøhvit management systems shall contribute to achieving good environmental performance. Management policy and commitment is built into the operations procedures and involves training of all staff to be aware of implications for the environment of their work. SEQUESTRATION OF CORBON DIOXIDE PRODUCED Beyond the Norwegian authority concessions conditions, Statoil will, when Snøhvit comes on stream, operate two large storages for CO2. One of the storages has been in operations for several years at the Sleipner field in the North Sea. However, for Snøhvit, it is the first time such CO2 technology is applied in the land based hydrocarbon industry. PS5-4.6

7 Statoil is of the opinion that such storages are contributing to the solving of the greenhouse gas problem and contributing to the governmental requirements according to the Kyoto Protocol. Treated as to LN process Acid Off as (CO2) CO2 compression Absorber Stripper Feed as Water Water Water Acid gas removal Amine regeneration Inlet separator Driers CO2 drying CO2 drying (regen. lines not shown) CO2 condensing subcooling and pumping CO2-product to pipeline for reinjection The process for removal of the reservoir CO2, with the drying and pressurization before exported for sequestration From the well stream content of 6-8 mol%, the CO2 in the gas feed to the LN process is reduced to 50 ppm, in order to have a margin towards freeze-out in the cryogenic section. This concept is conventional as for the absorption and stripping part. However, the CO2 stream from the stripper is, instead of being vented to atmosphere, further treated for re-injection into an offshore reservoir. When the water-saturated CO2 is leaving the stripper section of the removal unit, the pressure is close to atmospheric. The pressure is lifted up to 60 bars in a three-stage integral gear compressor. Between the 2nd and 3rd stage, CO2 is taken out for drying in an adsorption bed. In order to have a margin towards the solubility of water in the CO2, the drying specification is set to 50 ppm. Potential corrosion in the CO2 export line is very sensitive to water and free water in the CO2 may also lead to hydrate formation. After pressure increase to 60 bars, cold seawater is used to condense and sub-cool the CO2 before it is further lifted to the required export pressure by use of pumps, normally around 200 bars. The offshore CO2 injection system comprises of an eight inch pipeline over 160 kilometers to a manifold on one of the wellhead templates. Further the CO2 passes the choke module and the sub-sea control module, before passed down the re-injection well. PS5-4.7

8 FEED AS PRE-TREATMENT PROCESSES Before entering the liquefaction process, the feed gas must undergo stringent purification stages: CO2 removal De-hydration Mercury removal. When selecting technology for these units, high attention was given to environmental issues. Water removal Lean amin Feed as Water (regen. Lines not shown) Demin. water Wash water Treated gas Wash column CO2 absorber Rich amin Molecular Sieve Driers Molecular sieve Outlet filter CO2 removal Mercury Removal Mercury Adsorber outlet filter Feed to cryogenic units Conceptual solutions for feed gas purification CO2 removal With a content of up to 6 8 mol% CO2 in the feed gas and a requirement of 50 ppm CO2 in the purified stream, amine wash processes was identified as the most suitable design. Based on an overall lifecycle evaluation, the BASF amdea amine wash process was selected as the process for CO2 removal. Selection criteria for the process were: Environmental considerations Life cycle cost Energy consumption. PS5-4.8

9 In summary the benefits with the amdea process compared to normal solvents are: High process flexibility Low energy requirement High acid gas purity Low maintenance cost Low solvent losses Low/non toxic, biodegradable. The thermal heat for regeneration of amdea is provided by the flue gas heat recovery of the gas turbines, distributed via a hot oil system. Dehydration As the gas becomes water saturated in the amine wash unit, the de-hydration unit is located after the CO2 removal unit. Drying of the gas is performed by flow through a bed of water adsorbent agent. Two adsorption beds are operating, while one bed is regenerated by use of hot purified CO2, heated by a hot oil heat exchanger. Mercury removal Due to detectable traces of mercury (Hg) in the feed stream, a removal unit is installed as a protection. Double design margins is applied to maintain the integrity of the critical equipment made of aluminum in the cryogenic part of the plant, which otherwise can be threatened due to potential corrosion caused by accumulated mercury. The mercury guarding bed is located as close as possible to the units which it is protecting just upstream the low temperature units of the plant. THE LN LIQUEFACTION PROCESS In 1997 the Snøhvit project requested three contractors and LN process licensors to carry out conceptual designs for the base load LN plant located in Northern Norway. The licensed technologies evaluated were the propane pre-cooled mixed refrigerant process (C3MR), the optimized version of the classic cascade process (CCP) and finally the mixed fluid cascade process (MFC). The Hammerfest LN plant will be first reference for the Statoil-Linde developed LN process, named the Mixed Fluid Cascade (MFC ). An inherent characteristic of this process is low specific compressor power requirement. PS5-4.9

10 N Pre-cooling Section E1A E1B C1 CW1 Liquefaction Section E2 C2 CW 2A/B Sub-cooling Section E3 LN X1 C3 CW 3A/B The MFC process for Hammerfest LN plant The Snøhvit LN project, using the MFC process, will, from 2006, operate a very power efficient LN process. The refrigeration power input is 127 MW at a rated LN production of 4.3 mtpa. The specific power consumption is 0.23 kwh per kilogram LN produced. A reason for the efficient design is the low cooling water temperature and low air temperature over the year in Northern Norway. In the MFC process for train one of the Hammerfest LN plant, the compressor power is distributed 40% - 20% - 40% for the pre-cooling, liquefaction and sub-cooling respectively. In future development of the LN process, more optimized symmetric power distributions will be evaluated. A symmetric version will have a capacity of more than 7.5 mtpa of LN production, providing a good alternative for train expansion projects. enerally, there are three different ways of providing refrigeration for the liquefaction and sub-cooling, considering different licensed processes: 1. The first illustration is showing how the liquefaction and sub-cooling is arranged in both the C3MRC and DMR processes. This solution is limited to use equal boiling pressure for the liquefaction and the sub-cooling part. The refrigerant mixtures are created by the phase separation in a flash drum. The adaptation of optimal refrigerant mixture is limited to the selection of the MR for the whole cycle. The optimal operation will not occur before phase equilibrium is established in the flash drum. PS5-4.10

11 2. The MFC process, second illustration, does also use a constant refrigerant composition throughout the cycles, but can select individual refrigerant mixture and boiling pressure for the liquefaction part and the sub-cooling part. 3. The third illustration is showing a design, which is specifically adapted to the use of plate and fin heat exchangers. It is using the same constant refrigerant composition for the liquefaction and the sub-cooling part, but at different boiling pressures. The process does not rely on phase separation to provide optimal refrigerant composition. The comparisons between liquefaction and sub-cooling part in the MFC process and the two variations of dual mixed refrigerant (DMR) processes. POWER AND HEAT UTILITY SYSTEM Located in Norway, a country traditionally rich on, clean and green, hydro electric power, the evaluation of a possible provision of electric power to the LN plant from the national grid was mandatory. However, due to the remote location, including the general lack of robustness in the national grid in the northernmost regions, it was soon realized that a hydro electrical powered process was not feasible. It would require huge investments in the national power grid in order to supply the plant with reliable power according to the n-1 philosophy. However, the Hammerfest LN plant concept is an all-electric design, including the drivers of the liquefaction compressors. This concept eliminates the constraints of the individual sizing between liquefaction compressors and gas turbines in a mechanical drive configuration. The power and heat system is designed to provide a reliable, fully self-sufficient supply to the offshore transportation and the onshore processing and liquefaction of the PS5-4.11

12 gas and condensate production. The national grid is providing a certain backup of electricity to the LN plant. Aero-derivate gas turbines are selected for their high electrical power efficiency and the balance with heat demand in the plant, resulting in an excellent overall thermal efficiency for the LN plant. Electric motors, based on variable speed drive will contribute to an efficient use of power. Cold box Unit 25 Cycle compression and seawater cooling Unit 25 Electric power generation waste heat recovery, hot oil cycle Unit 81 and 50 N Electric Power ener. 5 x E LM 6000 T with waste heat recovery Plate Fin Heat Exchangers Precooling Cycle Sea water cooling M Air Fuel gas Spiral Wound Heat Exchangers enerator Liquefaction Cycle Subcooling Cycle PCC Compressor LCC Compressor M Hot oil cycle LN Expander/ enerator LN SCC Exp./ ener. SCC Compressor M Electric Power from the rid Process heat consumers The energy system and the LN process for the Hammerfest LN plant The selected energy system provides a condition of stable operation to the LN plant, improving the revenues by increased on-stream days. For the Snøhvit design, the availability of the all-electric concept is approximately ten on-stream days more per year than for a mechanical drive, industrial heavy-duty based concept, with gas- and steam turbines. This configuration of the energy system of the Hammerfest LN plant provides in normal operation, an electricity efficiency of 41% and an overall thermal efficiency of 71%, using hot-oil for the waste heat recovery system. The power and heat generation of the LN plant discharge tons per year of CO2 and 650 tons per year of NOx. The environmental consequences of these emissions have a high focus in the project. However, will an electrical efficiency of 41%, emissions PS5-4.12

13 are reduced to the minimum. Taking into account that the electrical power demand is the design parameter and that heat generation provides a certain surplus, no additional gas fired heater is demanded for operational purpose. Energy system design The energy system is a significant part of the Snøhvit project, and is optimized according to operational design criteria for a utility system with the requirements of high on-steam days per year. The selected concept includes five LM 6000 turbo-generators, at site rated capacity 46 MW each, providing electric power to an internal grid supplying the three variable speed motors of the refrigeration compressors. The gas turbines are equipped with hot-oil waste heat recovery system in the exhaust stacks. The five gas turbine-generators provide the electric power to the refrigeration compressors and other users, and the process heat required in the process plant. Installed power is 230 MW of electricity and 210 MW of recovered thermal heat. The average electrical load demand for the LN plant summarizes to 195 MW, together with a thermal heat demand of 167 MW. This gives full redundancy for the heat generation system without using additional firing or stand by boilers. Operations strategy During normal operation of the plant the five gas turbines will balance the power and heat demand of the plant. Normally, both turbines and waste heat recovery units will operate on part load, shearing the load equally. The gas turbines have a backup from the national electricity grid at a capacity of 50 MW. Under a fault condition, such as loosing one gas turbine, the grid has the capability to accept a step-load of 50 MW without disturbing either the internal or external grid parameters. Regarding the waste heat recovery, the remaining four units will pick up load and cover the plant demand. The access to power is therefore based on the strategy of 5 out of 6 units in operation. With the power as the governing design factor, the waste heat recovery system, equivalently, fulfills the strategy of 4 of out 5 units in operation. Power demand scenario The power and heat system configuration gives a good balance with respect to: Plant power and heat demand Seasonal changes in ambient condition Aging of gas turbines, leading to reduced power output Aging of the process, leading to increase in power demand Back-up in the power and thermal generation. PS5-4.13

14 MW Power Production and Demand Ambient temperature ref T90% Max Power eneratio Power demand WITH margin Power demand NO margin Power balance NO margin Power balance WITH margin -50 Month 1 is October Electric power load scenario For power demand, a minimum and maximum load scenario has been established: 1. Power demand with no margins represents the plant in up-and-running operation. 2. Power demand with guarantee margins represents the plant in normal operation, including process design margins and API margins in machinery design. Power and heat balances in summer and winter are evaluated based on the two power scenarios, including the aging factors and ambient conditions. For the ambient, the temperatures of 90% probability of not to be exceeded (T90) are used, as this would represent a conservative scenario, without installing too much over-capacity for the summer season. As the figure shows, there is a difference of approximately 10 MW between the two load scenarios. As the actual load for the plant is still unknown, it is expected that the operational load will be between the two curves. The system for power generation is designed in such a manner that the high load scenarios are covered. COST RELATED TO THE ENVIRONMENTAL STRATEY Stringent authority requirements combined with the environmental strategy of the project are setting frame conditions, which means additions investment costs. Some of the implemented techniques reflect life cycle cost robustness versus future trading of emission quota others do not. PS5-4.14

15 The cost of sequestration of the produced CO2 is USD 200 million, a significant part of overall EPC for the Snøhvit project development. Related to a potential cost level of international quota, the investment reflects years pay back, pointing at the Statoil corporate focus on immediate actions related to the environment. The investment in the electric generation and drive concept, balances in revenue at ten extra on-stream days per year. With the designed flexibility of the system, such operation should be fully obtainable. With the selection of the amdea, the requirement of heat is less than recovered from the gas turbines, eliminating the need for auxiliary firing, providing a cost efficient concept. The no-flare philosophy applied for the return gas from the LN carriers during loading is a cost increasing design. Investments in additional compressors and increased process capacity, is USD 7 million. Due to the intermittent operation and limited emissions, a pay back of 30 years reflects this investment. REFERENCES CITED W Förg, W Bach, R Stockmann, Linde and R S Heiersted, P Paurola, A O Fredheim, Statoil: A New LN Baseload Process and Manufacturing of the Main Heat Exchangers. LN 12 Conference, Perth, May R S Heiersted, R E Jensen, R H Pettersen, S Lillesund, Statoil: Capacity and Technology for the Snøhvit LN Plant. LN 13 Conference, Seoul, May PS5-4.15