海域天然气水合物开发的地球物理监测

• Main Authors: 何涛, 卢海龙, 林进清, 董一飞, 何健
• Other Authors: 北京大学地球与空间科学学院, 造山带与地壳演化教育部重点实验室,北京100871, 北京大学工学院能源与资源工程系,北京100871, 北京大学海洋研究院,北京100871, 中国地质调查局 广州海洋地质调查局,广东 广州,510760
• Format: Journal/Newspaper
• Language: English
• Published: 地学前缘 2017
• Subjects: 天然气水合物; 储层监测; 4分量海底时移地震系统; 海洋可控源电磁; 海底变形; gas hydrate; reservoir monitoring; 4-C OBC time-lapse seismic system; MCSEM; seafloor deformation; Canada; permafrost
• Online Access: https://hdl.handle.net/20.500.11897/483367; https://doi.org/10.13745/j.esf.yx.2016-11-27

作为极具潜力的未来清洁能源,海域天然气水合物开发难度大、环境保护要求高,需要大范围地对水合物储层进行动态监控.然而,虽然在国外的天然气水合物试开发时,曾尝试对储层进行监测,但主要是局限于开发井周边小范围监测.对天然气水合物藏的大规模监测,目前国内外都还没有建立起相关的技术系统,即使有关的研究都还很少.在未来的几年内,我国以及日本、韩国、印度等将在海域开展天然气水合物的长期试开发,在开发过程中对储层的大规模监测必不可少.本文从水合物藏的岩石物理特征出发,讨论了沉积物中水合物的饱和度和孔隙赋存状态对其声学和电学性质的影响规律,比较了基于水合物的地震和电磁性质的多种地球物理勘探手段应用于海域水合物藏大规模监测的可行性和利弊.针对我国南海天然气水合物生产试验和未来商业开发的储层监测需求,为实现对大区域水合物储层和海底变形的定量监测,我们设计的水合物试采过程监测系统由井中地球物理参量监控、三维全光纤4分量海底时移地震和海底多功能监测站三部分构成.该方案大量利用油气行业现有成熟技术,并对其进行优化设计,可实施性强,能够较全面地收集海域水合物开采过程中储层相关的基础数据,从而可为后续技术优化、水合物资源评价、海底环境保护、工程灾害预防等方面提供科学依据. Marine gas hydrate is an important resource of clean energy for the future,but its exploitation requires not only the innovation of development techniques but also serious consideration of protection of marine environment.For a timely response to production process,monitoring of the dynamic change of gas hydrate reservoir in real time is a basic requirement for a successful exploitation.However,in previous successful gas hydrate production experiments,either in terrestrial permafrost area (Mallik of Canada and Ignik Sikumi of USA) or on continental slope in deep sea (Nankai Trough of Japan),monitoring was carried out mainly through the instruments installed in the two or three observation wells which were only tens of meters away from the production well,and consequently the monitoring might have covered only a limited area.At the present the monitoring technique for large-scale monitoring of gas hydrate reservoir has not been established worldwide,even systematic discussion and scheme design are absent.Based on the acoustic and electrical responses to the saturation change and granular contact mode of gas hydrate layer,several seismic and electromagnetic exploration methods have been compared to see their feasibility and merits and drawbacks for large-scale monitoring of marine gas hydrate development,and an advanced geophysical monitoring scheme is proposed for the upcoming gas hydrate experimental production in South China Sea and future commercial exploitation.The integrated geophysical monitoring system is comprised of (1) a set of geophysical sensors to be installed in the observation wells,which will continuously collect the key physical parameters as temperature,pressure,electrical resistivity,streaming potential,heat flux,etc.;(2) a high sensitive and endurable full fiber 4-component ocean bottom seismic cable system to record the time lapse variations of reservoir acoustic properties of both compressive and shear waves;(3) a net of multifunctional ocean bottom nodes around the production well to measure the seafloor surface deformation/depression during production,and to directly detect and visually observe possible methane leakage.On a well designed protocol,this monitoring system can quantitatively measure the key geophysical variations associated with gas hydrate dissociation,and the data to be acquired will provide scientific basis for production optimization,environment protection and risk assessment for marine gas hydrate exploitation. 国家自然科学基金项目; 中国地质调查局国家天然气水合物专项 5 368-382 24