天然气水合物开采过程能源效率的关键影响因素及提高能效的方法

The exploitation of natural gas hydrate, a large-scale alternative energy resource, has been included in the national medium and long term science and technology development plan. However, to improve energy efficiency in production process remains one of the key issues concerning the commercial exploitation of natural gas hydrate. In this project, with respect to the three production modes, i.e., thermal stimulation-depressurization, flue gas purging-displacement, cycling production-steam reformation-CO2 + H2 injection-production, systematic multi-scale (multi-dimensional) simulations will be carried out for the process of gas recovery from hydrates. This would in turn reveal the behaviors of energy and mass transfer, phase change, separation of components as well as multiphase flow in reservoir in this process. Accordingly, mathematical models and measures of numerical stimulation can be developed. Next, thermodynamics concepts including exergy production, effective exergy production and effective exergy consumption will be introduced to evaluate the energy efficiency in recovery process of natural gas. Meanwhile, in order to improve the effective exergy production (i.e. energy efficiency) of the whole process, production is integrated with the disposal of harmful emissions from other processes in chemistry or energy industry. Finally, based on physical modeling and numerical simulations, methods for technological and economic assessment of production process could be developed using ratios of net exergy production/exergy consumption and effective exergy production/exergy consumption as indicators. In this approach, crucial factors affecting the technological and economic aspects of different production methods could be identified. Furthermore, process parameters for each unit in production procedures could be optimized with regard to reservoirs with different characteristics. The above work would give an answer to the generally concerned problem of the maximum potential of natural gas hydrate possible for energy use.

天然气水合物作为大规模接替能源，其开发利用列入国家中长期科技发展规划，提高开采过程能效是实现水合物商业开采的关键之一。本项目针对注热-降压开采、注烟道气吹扫-置换开采、天然气蒸汽转化和注CO2+H2联合循环开采三种模式，开展系统的水合物开采过程的多尺度（维度）模拟，揭示开采过程的能量/质量传递、相转变和组分分离、多相流体渗流规律，建立相应的数学模型和数值模拟手段。将㶲产、当量㶲产、㶲耗等热力学概念引入到水合物开采过程能源效率的评估，并将水合物开采过程和其它化工和能源过程的有害排放物的处置结合起来提高开采过程的当量㶲产即能源效率。建立基于物理模拟和数值模拟、以净㶲产/㶲耗和当量㶲产/㶲耗比为指标的水合物开采过程技术经济性评价方法，确定影响不同水合物开采模式技术经济性的关键因素、针对不同特征的矿藏进行各开采过程单元的工艺参数优化，回答天然气水合物最大可能的能源利用潜力这一被普遍关心的问题。

天然气水合物作为大规模接替能源，其开发利用已列入国家中长期科技发展规划，研发安全高效的开采方法、提高开采过程能效是实现水合物商业开采的关键。本项目针对注热-降压开采、注CO2混合气吹扫-置换开采天然气水合物两种模式，开展了系统的多尺度（维度）实验模拟研究，揭示了开采过程的能量/质量传递、相转变、组分分离和多相流体渗流规律，探究了提高天然气开采效率的方法手段，表明注CO2混合气吹扫-置换方法可显著提高甲烷采出效率；建立了注含CO2混合气开采天然气水合物的相关数学模型，开发了注气开采过程数值模拟方法，并成功用于注气开采过程数值模拟，结果也显示注气开采和传统降压或注热开采相比，甲烷的采出速率和累计产量均大幅提高；建立了考虑开采过程水合物储层形变的热-流-固耦合数值模拟方法，并成功用于降压开采过程数值模拟，模拟结果显示了考虑储层形变的十分重要性；建立了基于净㶲（有效能）产量、㶲效比的热力学分析方法及㶲产、㶲耗、废盐水和CO2埋存当量㶲的计算方法；进行了注CO2、烟道气、注热盐水开采甲烷水合物的综合能效分析，确定了影响能效的关键参数，提出了优化方案；完成了注H2+CO2混合气开采甲烷水合物耦合水蒸气重整制氢和CO2海底封存的全周期能效分析，表明CO2埋存能显著提高整个耦合过程的当量㶲效比；提出了高效分离CO2的新方法，开发了多种高效脱碳工作介质及相应的脱碳工艺技术，并推进了其工业应用。本项目研究丰富了天然气水合物开采相关的基础数据和规律性认识，为综合评价了不同水合物开采模式提供了理论方法，为安全、绿色高效开采天然气水合物提供了新的技术思路，为推进我国天然气水合物资源的开发利用发挥了作用。发表学术论文53篇，其中SCI收录论文52篇，国际会议特邀主题报告3次，国内学术会议特邀报告1次。申请中国发明专利11件（授权7件）、国际专利3件（授权2件），软件登记1件。获得省部级科技奖二等奖1项。