【作者】 李山；

【导师】 张荣；

【作者基本信息】 重庆大学 ， 应用经济学， 2021， 博士

【摘要】 走进厨房,点燃天然气灶,开始准备做饭,这是千家万户日常生活中很平常的事,偶尔遇上停气,供气公司也会提前告知并尽快恢复供气,人们似乎不用担心没有天然气可以使用。然而,由于全球天然气生产、消费存在明显的地区不平衡,许多国家的天然气消费严重依赖进口,这使得看似稳定可靠的天然气供应背后却常常伴随着天然气进出口大国博弈。我国自2006年开始天然气净进口,于2018年超过日本成为世界最大的天然气进口国,到2020年天然气对外依存度已超过42%。尽管我国通过投资和独特的外交手段获得了大量的海外天然气资源,但由于天然气进出口国在经济、政治、文化、宗教等方面的差异,使得天然气出口国对不同的天然气进口国可能表现出不同的出口偏好,这种与地缘政治等相关的出口国偏好成为影响天然气供应安全的重要因素之一。而另一方面,为了保障天然气供应的可靠性,进口国经常以天然气储备作为应对天然气供应中断的重要手段,近年来国内外天然气市场的不确定性使得天然气储备备受关注,而进口国的这种储备行为的变化也会对天然气市场产生重要影响。基于此,本文主要从天然气出口国偏好和进口国储备的视角,从理论上分析不同信息结构下天然气贸易博弈。首先从进出口国单纯追求利润最大化的角度出发,构建并分析了天然气贸易多国动态博弈模型,然后将出口国偏好这一重要因素引入天然气贸易动态博弈,分析其对进出口国均衡策略的影响,最后通过构建两个博弈模型,从理论上分别分析了进口国储备以及储备偏好对天然气进出口均衡策略的影响。具体分析和结果包括以下四个方面:第一、纯利润目标影响下的天然气进出口博弈。构建了单纯追求利润最大化的天然气进出口大国动态博弈模型,求解了模型在同时博弈以及出口国作为主者的主从博弈这两种不同信息结构下的状态反馈均衡解。结果表明,在两种不同信息结构下,该模型均存在唯一的状态反馈均衡解;天然气贸易市场集中度越高,出口国天然气开采收敛速度越慢;与同时博弈相比,主从博弈下进口国的总福利更小,出口国的总利润反而更大,进出口国的福利总和也更大;在主从博弈下,随着进口国数目的增加,出口国将失去其作为主者的先行优势,整个市场更接近同时博弈的情形。第二、出口偏好和供应不足风险下的天然气进出口博弈。考虑到天然气出口国国内也可能面临天然气供应不足的风险,将出口国天然气供应不足风险和出口偏好纳入统一的动态博弈模型,分析了同时博弈以及主从博弈这两种不同信息结构下的状态反馈均衡策略及其政策含义。研究发现,供应不足风险会削弱主从博弈主者的优势同时减少从者的劣势,而出口偏好则会强化主从博弈主者的优势同时加大从者的劣势;天然气开采收敛速度随供应不足风险的增加而降低,随出口国偏好的增加先上升然后再下降;从天然气进出口国福利总和的角度来看,同时博弈优于主从博弈。第三、进口储备及开采技术投资影响下的天然气进出口博弈。基于天然气进口国为了经济利益和供应安全对天然气进行储备和价格管制,而追求经济利益最大化的天然气出口国对天然气开采进行技术投资,构建了天然气进出口国的动态博弈模型,并运用最优控制理论分析了进口国最优天然气消费与储备路径以及出口国最优技术投资与最优出口路径。研究表明,出口国投资效率和投资成本系数以及进口国储备偏好和销售价格对天然气进出口策略有重要影响,进口国储备稳态效用和总效用与销售价格之间均呈倒“U”型关系,且前者达到最大值时的销售价格低于后者;政府对天然气市场不适当的价格管制可能会使得天然气储备功能与预期存在偏差,甚至导致与预期完全相反的结果。研究还发现,虽然出口国可以通过垄断势力规避天然气进口国因价格管制等带来的不利影响,但同时也可能因此失去进口国因其储备偏好变化而增加的市场份额。第四、进口国储备偏好影响下中国与欧盟天然气进口博弈。鉴于中国目前是世界第一大天然气进口国,但与欧盟相比,天然气储备水平依然很低。为了应对各种不确定性以保障天然气的稳定供应,中国天然气储备水平未来将会有明显提升。中国天然气储备水平的变化将引起天然气进口需求的变化,进而通过中俄管道天然气的贯通影响欧盟天然气的进口策略。为了从理论上分析中国天然气储备偏好变化对不同信息结构下天然气进口博弈的潜在影响,构建了中国与欧盟在俄罗斯天然气市场上的进口博弈模型。研究表明,当只有中国调整储备偏好时,中国在同时博弈中所获得的利润可以达到在主从博弈中主者的利润水平,此时欧盟的利益会受到损害;而当中国和欧盟均可以调整储备偏好时,中国和欧盟的均衡利润可能因为过度储备反而降低,俄罗斯则可能因此而获得更多的生产者剩余。随着我国经济增长和碳排放等环境压力的增大,天然气有望成为未来数十年增长最快的化石能源,供需缺口可能还会继续增大,进口依存度还可能进一步上升。本文主要从出口国偏好和进口国天然气储备的视角对天然气贸易博弈进行了一定理论分析,这有助于理解和完善天然气贸易博弈理论,同时也有助于为进出口国保障天然气供应安全提供一定借鉴。更多还原

【Abstract】 Walking into the kitchen,lighting the natural gas stove and preparing to cook,which is a very common thing for thousands of families in the daily life.When the natural gas supply is cut off occasionally,the gas supply company will inform us in advance and restore the gas supply as soon as possible.People do not seem to worry about there is no gas to use.However,due to the obvious regional imbalance in the global production and consumption of natural gas,many countries rely heavily on the import of natural gas,which makes the seemingly stable and reliable natural gas supply often accompanied by the natural gas import and export game among big powers.China has become a net importer of natural gas since 2006,and surpassed Japan in2018 to become the world’s largest natural gas importer.And China’s external dependence on natural gas has exceeded 42% by 2020.Although China has obtained a large amount of overseas natural gas resources through investment and unique diplomacy.However,due to the differences in economic,political,cultural,religious and other aspects between natural gas importers and exporters,the natural gas exporters may show distinct export preferences to different natural gas importers.The export preference related to geopolitics has become one of the important factors affecting the reliability of natural gas supply.On the other hand,in order to ensure the reliability of natural gas supply,the importers often use the natural gas reserve as an important means of coping with gas supply interruptions.In recent years,the uncertainty of the global natural gas market makes the natural gas reserve attract much attention.Moreover,such a change in the gas reserve behavior of importers will have an important impact on the natural gas market.From this,this paper mainly analyzes the natural gas trade game under different information structures from the perspective of the natural gas exporter’s export preference and importer’s gas reserve.Firstly,from the perspective of the importers and exporters simply pursuing profit maximization,a multi-country dynamic game model of natural gas trade is constructed and analyzed.Then,the export preference as an important factor is introduced into the dynamic game of natural gas trade,and its influence on the equilibrium strategy of importers and exporters is analyzed.Finally,by constructing two game models,the effects of importer’s gas reserve and reserve preference on natural gas import and export equilibrium strategy are analyzed theoretically.The specific analysis and results include the following four aspects:Firstly,the natural gas import and export game under the influence of a pure profit target.In this part,a dynamic game model in which the importers and exporters simply pursue profit maximization is constructed,and the state feedback equilibrium solution of the model is solved under two different information structures: a simultaneous game and a Stackelberg game in which exporter is the leader.Results show that,under these two different information structures,this model has a unique state feedback equilibrium solution.The higher the concentration degree of the natural gas trade market,the slower the convergence rate of exporter’s gas exploitation.Compared with the simultaneous game,the total welfare of the importer is smaller,but the total profit of the exporter is larger,and the sum of the welfare of the importer and exporter is also larger.In the Stackelberg game,as the number of importers increases,the exporter will lose its advantage of being the leader,and the whole trade market is closer to the situation of the simultaneous game.Secondly,the natural gas trade game with export preference and insufficient supply risk.Considering that the natural gas exporter may face the risk of insufficient natural gas supply at home,this paper integrates the exporter’s insufficient supply risk and export preference into a unified dynamic game model,and analyzes the state feedback equilibrium strategy and its policy implications under two different information structures: a simultaneous game and a Stackelberg game.The study finds that the insufficient supply risk can weaken the advantage of the leader in the Stackelberg game and reduce the disadvantage of the follower,while the export preference can strengthen the advantage of the leader and increase the disadvantage of the follower.The convergence rate of natural gas exploitation decreases with the increase of insufficient supply risk,and it rises first and then falls with the increase of export preference.From the sum of the welfare of the importer and exporter aspect,the simultaneous game is better than the Stackelberg game.Thirdly,import and export strategy under natural gas reserve and exploitation technology investment.Based on the natural gas importer carries out reserve and price control for the sake of economic benefit and supply safety,while the natural gas exporter invests in exploitation technology to maximize economic benefit.Under this condition,a dynamic game model of an importer and an exporter is presented.The optimal control theory is used to analyze the optimal natural gas consumption and reserve of the importing country,as well as the optimal technology investment and export quantity of the exporting country.The research shows that the investment efficiency and the investment cost coefficient,as well as the reserve preference and selling price,have an important influence on the import and export strategy.The steady-state utility of reserve and the total utility of the importer are both inverted “U”with the selling price.And when the former reaches the maximum,the selling price is lower than that of the latter.The importer’s price control may cause the reserve to deviate from its initial purpose,and even lead to a result completely opposite from the expected.The study also finds that,while the exporter could use its monopolistic power to avoid the adverse effects generated by the gas importer,such as price controls,it may also lose the potential increase in market share due to changes in the importer’s reserve preference.Fourthly,game of natural gas import between China and the EU under reserve preferences.China is currently the world’s largest natural gas importer,but its gas reserves are relatively low compared with the European Union.To ensure its reliable gas supply,China will raise its gas reserves significantly in response to uncertainties in the future.A change in China’s natural gas reserve level will change the global natural gas market demand.And this will also affect the EU’s gas import strategy because now Russia’s pipeline natural gas is connected to China.To theoretically analyze the potential impact of China’s natural gas reserve on different gas import games with different information structures,an import game model between China and the EU in the Russian natural gas market was established.The research shows that when only China can adjust its reserve preference,its benefit in a simultaneous game could reach that of the leader in a Stackelberg game,but the EU’s benefit will shrink.If both China and the EU are allowed to adjust their reserves,both profits may fall due to excessive reserves,but Russia’s producer surplus will rise.With the increase of China’s economic growth and increasing environmental pressure such as carbon emissions,natural gas is expected to be the fastest-growing fossil energy source in the coming decades.Therefore,the gap between China’s gas supply and demand may continue to increase,and the gas import dependence is likely to rise further.This paper makes a theoretical analysis of the natural gas trade game from the perspective of the natural gas exporter’s export preference and importer’s gas reserve,which is helpful to understand and perfect the natural gas trade game theory,and it also helps to provide some reference for importers and exporters to guarantee the security of natural gas supply.更多还原