海底冷泉羽状流及其资源效应探讨

Discussion on the submarine bubble plume and its effect on hydrocarbon resources

海底冷泉羽状流是海底冷泉活动最直接的表现形式,与天然气水合物动态成藏和动态油气系统密切相关.近年来,因其对全球气候变化的影响和潜在的资源前景,冷泉流体活动受到越来越多重视.本文对全球重要海域海底冷泉羽状流的分布和通量相关研究进行总结分析,发现冷泉羽状流广泛分布在主动和被动大陆边缘,而在弧后地质背景和走滑大陆边缘发现较少,研究不够深入.在构造活动活跃、沉积速率和运移通道渗透率高的地质背景下,冷泉羽状流一般呈区域性聚集发育,规模与通量较大.目前研究发现,通常单个羽状流渗漏孔的通量一般介于3.5 mL/min~13.9 L/min之间,但受制于观测技术和成本,羽状流的通量估算具有不确定性,且易受到不同地质和海洋控制因素的影响.另外,冷泉羽状流发育区往往对应或指示重要海洋油气富集区,通过与海域天然气水合物试采结果和天然气水合物工业生产指标进行对比分析,认为大型单体冷泉羽状流以及与水合物赋存或深部油气藏相关的区域性羽状流群具有重大资源效应,主要体现在羽状流本身的气体通量资源效应、与天然气水合物的密切联系以及对于海洋深部动态油气藏的指示三个方面.建议重视对海底冷泉羽状流发育区的调查与探测,尤其针对大型单体冷泉羽状流,加强对其活动特征的长期观测,从而明确其时序渗漏特性、活动机制以及海洋与地质因素的控制作用.通过研究有效的通量测量技术和方法,建立冷泉羽状流资源评价技术标准,从而推进其进一步开发与利用.

As the most direct manifestation of active cold seeps, submarine cold seep bubble plumes are closely associated with the dynamic accumulation of natural gas hydrate and petroleum system. Due to its impact on global climate change and its hydrocarbon potential, cold seeps have drawn more and more attention in recent years. Based on the studies from major sea areas in the world, this paper summarizes and analyzes the distribution and flux of submarine cold seep plumes, which shows that the cold seep plumes are widely developed along the active and passive continental margins, but less on the transform continental margins and back-arc basins. Cold seep plumes with large fluxes tend to cluster in the geological settings with active tectonic activities, high sedimentation rates and massive migration pathways with high permeability. Generally, the flux range of a single seep hole varies from 3.5 mL/min to 13.9 L/min. However, due to the limitation of observation technology and cost, the estimations on the flux of plumes have great uncertainty and are easily affected by different tectonic and oceanographic factors. In addition, the areas of cold seep plumes often correspond to or indicate important marine oil/gas enrichment areas. By comparing the results of the production test of gas hydrates and the corresponding industrial production index, the individual cold seep plumes with large fluxes or the plume clusters in relation to hydrate occurrence and deep hydrocarbon reservoirs have significant resource effect, i. e. the flux of the plumes themselves,their close relationship with natural gas hydrate,and the indication of dynamic oil and gas reservoirs at greater depths. To figure out the spatiotemporal characteristics and dynamic mechanisms of seabed fluid escapes,as well as the oceanographic and geological controls, more attention should be paid to the investigation of submarine cold seep plumes,especially large-scale submarine cold seep plumes,and enhance long-term observations on their temporal activity. Moreover, the study on the efficient technologies of flux measurement,as well as the resource evaluation of cold seep plumes will promote further development and utilization.