青海永久冻土区天然气水合物开发的环境影响风险防治

青海省祁连山南缘多年冻土区发现天然气水合物,这是在我国冻土区的首次发现.虽然青海天然气水合物的发现与开发具有诸如能源战略等重要意义,但在多年冻土区开发天然气水合物具有巨大的环境影响风险,包括CH4释放对全球气候的影响、冻土层的退化和高寒草甸的破坏、开采过程中可能出现的塌方和地陷等.可以通过采用安全可靠的具有针对性的开发技术和工艺,将青海天然气水合物开发纳入柴达木循环经济范畴,采用CO2捕获和封存技术,以及控制工程过程等来防治天然气水合物开发过程中的环境影响.

Environmental impacts and management of gas hydrates exploitation in Qinghai Province permafrost

Gas hydrate samples were collected in Muli area of the Southern Qilian Mountains permafrost of Qinghai Province,and which is the first discovery of gas hydrate in Chinese permafrost and in the low to middle latitude permafrost of the world.Although the exploitation of gas hydrate in Qinghai Province has lots of important significance,such as energy strategy and carbon reduction,huge environmental impacts will take place in the exploitation.To study the potential environmental impacts is significant to explore the new deposits,to institute an available scheme for gas hydrate exploitation,and to protect Tibetan Plateau environment in these foregoing processes.In the text,the characteristics are analyzed of gas hydrate in Qinghai Province permafrost and natural environment in Tibetan Plateau,and three main risks are considered for environment accompanying gas hydrate exploitation,which include as follows:(1) global climate influence due to natural gas emission when the temperature and pressure of gas hydrate changed and became unstable;(2) permafrost and alpine meadow ecosystem degeneration for global climate warming and engineering process influences,and(3) ground collapse and depression in gas hydrate mine goal area.In order to avoid or decrease the risks and achieve benefits from gas hydrate exploitation in Qinghai Province,the following works should be done:(1) Safe and dependable exploitation technique should be adopted.In Muli area,gas hydrate samples were found in the cracks of siltstone,mudstone or shale,and were presented as thin layer,sheet,conglomeration,or disseminated in siltstone.Replacement of CH4 from hydrate with CO2 is an available method to exploit the gas hydrate since it could contact and act with CO2 fairly for its mode of occurrence.(2) Many industries have been established intensively in Qaidam circular economy zone,and they need large amounts of energy and release huge amounts of high concentration CO2.Thus,bring gas hydrate exploitation into Qaidam circular economy and adoption carbon capture and storage technology could reduce the risk of atmosphere influence for the decreased volume of CO2 released to atmosphere.(3) Environment and ecology in Tibetan Plateau is very weak,and the restoration is difficult if it has been destroyed.Therefore,the process of engineering must be controlled during the exploitation,such as to occupy and to dig land as small as possible,to decrease mechanical vibration,and to use the experience of railway construction on Tibetan Plateau for reference.(4) Because of absence of law for gas hydrate,to legislate is important for its prospecting and exploitation.(5) To formulate emergency preparatory scheme could cope with the happened risk and decrease the loss.To be brief,much attention should be paid to the following works: possible risks prediction,their hazard level evaluation and emergency preparatory scheme formulation before exploitation,the exploitation should be organized and monitored carefully,the personnel and material should be prepared well for emergency preparatory scheme in the exploitation process,the emergency preparatory scheme should be started and acted in close coordination in order to reduce the loss to the lowest after the risks appeare.