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首页> 外文会议>IAEE international conference;International Association for Energy Economics >ENVIRONMENTAL FOOTPRINT OF GAS TRANSPORTATION: LNG VS. PIPELINE
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ENVIRONMENTAL FOOTPRINT OF GAS TRANSPORTATION: LNG VS. PIPELINE

机译：天然气运输的环境足迹：液化天然气与天然气。管道

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OverviewThe share of natural gas has been steadily growing in the European energy mix: from 17,8% in 1990 to 23,2% in 2013 (Eurostat, 2015). Natural gas attracts increasing attention because of higher efficiency and a low CO_2 impact in comparison to coal and oil. In May 2015, Norway overtook the Russian position of the main gas supplier to Western Europe. Most of the Norwegian gas is transported via an extensive export pipeline system to Europe, and a small fraction (less than 4%) is exported in liquid form (LNG) by special ocean-going tankers to the US, Europe, Japan, etc. The need for new gas transport infrastructure on the Norwegian continental shelf (NCS) and strict environmental policy targets justify a study of the environmental performance of alternative modes of gas transportation. The aim of this study is to estimate emissions of CO_2 and NOx caused by processing and transportation of a unit of dry gas in either a gaseous form via a pipeline, or as LNG with ships from the NCS to relevant markets.MethodologyDue to the fact that the wellstream to a certain extent is processed on platforms the processing related emissions cannot be fully separated from the production related emissions. Therefore, this study also includes the emissions related to production, excluding emissions related to the drilling of production wells. Exploration (seismic surveys by special ships, exploration drilling) and support activities provided by supply vessels and helicopters are also excluded from the analysis, based on the assumption that these activities are common to the pipeline and LNG chains. The emissions of pipelines chains are estimated through adding up emissions from production, processing, and pipeline transportation segments. The analysis of the LNG chain includes emissions from production, processing, liquefaction, sea-shipping, and regasification. The analysis is based on publicly available industry data, mainly annual reports of the operators on the NCS to the Norwegian Ministry of Climate and Environment (2014). It gives this study an advantage of using field- and facility-specific emission factors and values measured at site, instead of theoretical parameters. The estimates are adjusted for the associated oil and condensate production.In order to perform a reasonable comparison, we consider seven pipeline chains (Table 1), because technologies of the pipeline gas processing are not uniform on the NCS. The differences are determined by numerous factors such as the composition of the gas, the type of well, the distance from the shore, sea depth, and transportation solutions available. At the Åsgard, Statfjord, Troll, Kvitebjørn, and Aasta Hansteen fields, the water and parts of natural gas liquids (NGLs) are separated from the wellstream at the offshore platform, the remaining rich gas is transported via rich gas pipelines to onshore facilities for further processing. When the remaining NGLs are removed, dry gas (methane and some ethane) is transported via dry gas pipelines to Europe. At the Sleipner Øst field, the wellstream is processed offshore, dry gas is sent directly to the continental Europe via the transmission pipelines, while NGLs and condensate are shipped by vessels. The Ormen Lange field does not have any processing steps offshore – the unprocessed wellstream is directly sent via a field-dedicated multiphase pipeline to the processing facility onshore. Some fields (Ormen Lange and partially Troll) are connected to the main electricity network onshore, the majority use gas turbines for power generation. All processing plants (Kollsnes, Nyhamna, and Kårstø) use power from the main grid; however, the Kårstø plant uses gas turbines for export compression.There is only one LNG chain on the NCS, which produces gas from the Snøhvit field. As the estimates are sensitive to the distance over which LNG is shipped, we consider two existing shipping routes: to the Iberdrola terminal in Spain and to the Cove Point terminal on the western USA; and one hypothetical route to Zeebrugge in Belgium (which represents a close comparison to the pipeline alternative).ResultsThe description of the considered chains and total specific CO_2 and NOx emissions are presented in Table 1. Generally, pipeline transportation outperforms LNG supply chains with respect to emissions. An exception is theStatfjord pipeline chain. The comparatively high specific emissions for this chain are due to the offshore productionsegment. 85,1% of the CO_2 and 96,8% of NOx emissions are related to this activity. This can be explained by the ageof the field – it is one of the oldest on the NCS, with much lower energy efficiency compared to newer fields. At theoffshore production stage, 82,1% of CO_2 and 94,5% of NOx emissions are attributed to the power generation by gasturbines. Similar considerations are related to the other fields connected to the Kårstø plant, the Åsgard chain:offshore production causes 66,4% of the CO_2 and 80,8% of the NOx emissions, most of which are due to the powergeneration. Such proportions are explained by the high energy requirements of the gas transportation over the longdistances to the processing plant. The other pipeline chains, which include the Kollsnes plant, show significantlybetter results. The fields are rather close to the shore, requiring less power for transportation to the processing plant.Another reason is that gas compression for export to Europe is driven by energy from the main grid, as opposed tothe Kårstø plant, where export compressors are driven by gas turbines. The «cleanest» of the pipeline supply chainsis the Ormen Lange chain. It is due the proximity of the field to the shore and a technology with a subsea installation,which allowed avoiding any processing offshore. The Nyhamna plant uses the hydroelectric power from the maingrid, producing emissions only due to gas flaring for the safety reasons and some gas combustion in processingequipment. However, this chain is rather an exception. Another field connected to the Nyhamna plant is AastaHansteen, a mid-size field, which comes on stream in 2017. Because of the distance from the shore, it requiresenergy production on site, which causes 94,2% of CO_2 and 93,1% of NOx emissions.The Hammerfest LNG facility, which receives the unprocessed wellstream from the Snøhvit field, produces powerfor processing and liquefaction by gas turbines. For the Cove Point chain, this segment causes 55,3% of CO_2 and25,7% of NOx, shipping for the 4072 nautical miles adds 37% of CO_2 and 38% of NOx, the remaining 7,7% of CO_2and 36,3% of NOx are due to regasification.ConclusionsSeveral important aspects are left out of the scope of this paper. Among them are the differences of the CO_2 contentin the dry pipeline gas and LNG, which lead to different emission intensities of the combustion for the final use.Another aspect is the indirect emissions associated with construction and decommissioning of the infrastructure,which, however, might be negligible because of a long life-time of the facilities and high production volumes. Theobtained results represent the main picture and allow drawing some conclusions. Though a pipeline itself does notproduce any emissions during normal operations, as opposed to the LNG shipping, the environmental impacts of thepipeline transportation are not negligible. The scale of environmental advantages of the pipeline transportation overthe LNG strongly depends on the location of the field, technology applied, and the energy source used for exportcompression. Though, according to the regulation, each project on the NCS is assessed for the opportunity to getpower from the main grid, in many cases it is either technologically not possible or economically not viable due tothe distances to the shore, leading to considerable emissions from both for the pipeline and the LNG transportationalternatives.
机译：概述 天然气在欧洲能源结构中的份额一直在稳步增长：从1990年的17.8％到2013年的23.2％（欧盟统计局，2015年）。与煤和石油相比，天然气由于具有更高的效率和较低的CO_2影响而引起了越来越多的关注。 2015年5月，挪威取代了俄罗斯成为西欧主要天然气供应商的位置。挪威的大部分天然气都是通过广泛的出口管道系统输送到欧洲的，而一小部分（不到4％）是由特种远洋油轮以液态（LNG）的形式出口到美国，欧洲，日本等的。挪威大陆架（NCS）上对新的天然气运输基础设施的需求以及严格的环境政策目标证明了对替代天然气运输方式的环境绩效进行研究的合理性。这项研究的目的是估计由处理和运输单位形式的干气以气态形式通过管道或以液化天然气的形式从NCS到相关市场的运输所引起的CO_2和NOx排放。 方法 由于井流在一定程度上是在平台上进行处理的，因此与处理相关的排放不能与生产相关的排放完全分开。因此，本研究还包括与生产有关的排放，不包括与钻探生产井有关的排放。基于假设这些活动是管道和LNG链共同的假设，分析中也排除了供应船和直升机进行的勘探（特种船的地震勘测，勘探钻探）和支持活动。管道链的排放量是通过将生产，加工和管道运输部门的排放量相加来估算的。 LNG链的分析包括生产，加工，液化，海运和再气化的排放。该分析基于公开的行业数据，主要是NCS运营商向挪威气候与环境部提交的年度报告（2014年）。它为这项研究提供了一个优势，即使用特定于现场和设施的排放因子和现场测量的值，而不是理论参数。估计值针对相关的石油和凝析油产量进行了调整。 为了进行合理的比较，我们考虑了七个管道链（表1），因为在NCS上管道气体处理技术并不统一。差异取决于许多因素，例如天然气的成分，井的类型，与海岸的距离，海深和可用的运输解决方案。在Åsgard，Statfjord，Troll，Kvitebjørn和Aasta Hansteen气田，水和部分天然气液体（NGL）在海上平台与井流分离，剩余的富气通过富气管道输送到陆上设施以供使用进一步处理。除去剩余的NGL后，干燥气体（甲烷和一些乙烷）通过干燥气体管道输送到欧洲。在SleipnerØst油田，井流在海上进行处理，干气通过传输管道直接输送到欧洲大陆，而NGL和冷凝液则通过船运。 Ormen Lange油田在海上没有任何处理步骤-未处理的井流通过专用于现场的多相管道直接发送到陆上的处理设施。一些领域（Ormen Lange和部分Troll）连接到陆上主要电网，大部分使用燃气轮机发电。所有加工厂（Kollsnes，Nyhamna和Kårstø）都使用主电网的电力。但是，Kårstø工厂使用燃气轮机进行出口压缩。 NCS上只有一条LNG链，可从Snøhvit气田生产天然气。由于估算值对液化天然气的运输距离很敏感，因此我们考虑了两条现有的运输路线：去往西班牙的Iberdrola码头和去至美国西部的Cove Point码头;一条假想的通往比利时Zeebrugge的路线（与管道的替代方案进行了比较）。 结果 表1中列出了所考虑的链条以及总的特定CO_2和NOx排放量的描述。通常，在排放方面，管道运输的表现优于LNG供应链。一个例外是 Statfjord管道链。该链的特定排放量较高是由于离岸生产 部分。此活动与85.1％的CO_2和96.8％的NOx排放有关。这可以用年龄来解释 它是NCS中最古老的领域之一，与新领域相比，其能源效率要低得多。在 离岸生产阶段，天然气发电产生了82.1％的CO_2和94.5％的NOx排放 涡轮机。类似的考虑也与连接到Kårstø工厂的其他领域（Åsgard链）有关： 离岸生产原因66，CO2的4％和NOx排放的80.8％，其中大部分是由于电力 一代。长期以来，天然气运输对能源的高要求解释了这种比例 到加工厂的距离。其他的管道链，包括科尔斯内斯工厂，也显示出了显着的优势。 更好的结果。这些田地离海岸很近，运输到加工厂所需的电力更少。 另一个原因是出口到欧洲的天然气压缩是由主电网的能源驱动的，而不是 在Kårstø工厂，那里的出口压缩机由燃气轮机驱动。管道供应链中“最清洁”的 是Ormen Lange连锁店。这是由于田野靠近海岸以及具有水下安装技术的缘故， 这样可以避免在海上进行任何处理。 Nyhamna工厂使用来自主电厂的水力发电 电网，出于安全原因，仅由于气体燃烧而产生排放，并且在处理过程中会燃烧一些气体 设备。但是，该链条是一个例外。与Nyhamna工厂相关的另一个领域是Aasta Hansteen是中型油田，将于2017年投入生产。由于距海岸较远，因此需要 现场产生的能源，造成94,2％的CO_2和93,1％的NOx排放。 Hammerfest液化天然气设施从Snøhvit油田接收未经处理的井流，可发电 用于燃气轮机的加工和液化。对于Cove点链，此段会导致55.3％的CO_2和 25.7％的NOx，在4072海里的运输中增加了37％的CO_2和38％的NOx，其余的7.7％的CO_2 36.3％的NOx归因于再气化。 结论 几个重要方面不在本文的讨论范围之内。其中有CO_2含量的差异 干管道中的气体和液化天然气会导致最终用途的燃烧排放强度不同。 另一方面是与基础设施的建设和退役相关的间接排放， 但是，由于设备使用寿命长和产量高，可以忽略不计。这 获得的结果代表了主要情况，并可以得出一些结论。虽然管道本身不 与液化天然气运输相反，在正常运行期间产生任何排放， 管道运输不可忽略。规模以上管道运输的环境优势 液化天然气在很大程度上取决于油田的位置，所应用的技术以及用于出口的能源 压缩。不过，根据规定，NCS上的每个项目都会经过评估，以获得获得 主电网供电，在许多情况下，由于以下原因，这在技术上是不可能的，或者在经济上是不可行的 到海岸的距离，导致管道和液化天然气运输产生大量排放物 备择方案。

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