天然气水合物新型联动开发系统可行性研究

Feasibility Study on New Co-Development System of Natural Gas Hydrate

天然气水合物是天然气(主要成分甲烷)和水在极地、高原冻土带环境和深水地层内的高压、低温环境中形成的一种类似"冰笼"状的固体化合物,属于一种具有替代传统燃料的巨大资源潜力的新型、高效清洁能源。目前已形成了降压法、热激发法、CO2置换法等一系列天然气水合物开发技术,但出于技术性或经济性考虑,单独使用某一开发技术难以实现对天然气水合物的持续、稳定、经济开发。提出了天然气水合物新型联动开发系统,以降压法为基础,充分利用热电厂的高温流体和分布式热源进行热激发,同时将电厂捕集的CO2注入海底,采用"降压-热激发-CO2置换"联合法,提高海底天然气水合物的开采效率。新型联动开发系统主要实现热量循环系统、CO2-CH4碳循环系统和流体循环系统等三大循环系统。可行性分析结果表明,由于电厂余热提供的热能满足注热功率的最低要求,并且注入的CO2可进一步提高CH4产气率,因此新型联动开发系统在技术上可行;由于采用充分利用电厂余热的热流体激发法,因此新型联动开发系统在经济上可行;由于可促进电厂对CO2的捕集,并利用CO2取代CH4水合物的自发转化优势将CO2稳定封存于海底,相当于实现了电厂碳的"零排放",因此新型联动开发系统在环保方面也具有可行性。

Natural gas hydrate,a kind of CH4-H2O ice-cage-like solid compound formed under high pressure and low temperature in the polar,plateau permafrost or deep-water environment,belongs to a new type of efficient clean energy with huge resource potential to replace traditional fuels.A series of natural gas hydrate development technologies have been developed,such as depressurization method,thermal stimulation method and CO2replacement method.However,none of these methods could be utilized alone to achieve the sustainable,stable and economic development of natural gas hydrate due to technical or economic considerations.A new co-development system for natural gas hydrate was put forward,which makes full use of the high temperature fluid and distributed heat sources of thermal power plant for thermal stimulation based on depressurization method,while CO2captured in the power plant is injected into the sea floor,so as to improve the exploitation efficiency of marine natural gas hydrate using the combined method of depressurization,thermal stimulation and CO2replacement.The new co-development system mainly consists of three circulation systems,namely heat circulation system,CO2-CH4carbon circulation system and fluid circulation system.The feasibility analysis shows that the system is technically feasible because the thermal energy provided by the waste heat in power plant meets the minimum requirements of the natural gas hydrate development and the CO2injected can further improve the gas production of CH4.The system is economically feasible because it adopts the thermal-fluid stimulation method which makes full use of the waste heat in power plant.And the system is also environmentally feasible because it can promote the capture of CO2in power plant and stably sequester CO2under the sea floor in the form of CO2-hydrate by replacing the previous CH4-hydrate,equivalent to the achievement of zero CO2emission in power plant.