Abstract: A new style of overpressure fluid flow, namely late-stage overpressure fluid flow, was found and verified in Yinggehai Basin on the basis of comprehensive study of the formation pressure structure, distribution and development mechanism of diapers, and the effects of overpressure fluid flow. Different from the overpressure fluid flow model of Cartwright, the overpressure fluid flow in Yinggehai Basin was in a closed system in the early stage and expulsed in a focused manner through diapers in the late stage. The focused flow of overpressure fluids resulted in the late-stage, episodic and rapid accumulation of natural gases. The trap of DFl-1 gas field was formed in the Quaternary, and the minimum average injection rate of the DFI-1 gas field was estimated to be up to 140 cubic meters per day. The inter-reservoir compositional heterogeneities,the transient state thermal effects resulted from fluid activities and the strong migration fractionation reflected the non-continuous fluid flows,rapid changes in temperature-pressure conditions during fluid migration and inter-action of multi-stage injected fluids, which could become the effective parameters for identifying episodic fluid migration.

Key words: overpressure fluid, diaper, fluid flow, natural gas, late-stage rapid accumulation, Yinggehai Basin

摘要： 对莺歌海盆地地层压力结构、底辟分布与发育机理及超压流体流动效应的综合研究揭示并证明了一种新的超压流体流动样式,即晚期汇聚型超压流体流动。该模式与超压流体从浅埋藏(<1000～1500m)开始、在盆地范围内普遍排放的Cartwright模式明显不同,莺歌海盆地超压流体早期被封闭,晚期通过底辟集中排放,超压流体的汇聚导致天然气的晚期幕式快速成藏。对东方1-1气田的圈闭构造分析表明,该气田形成于第四纪,其最低平均充注速率达140m³/d。成藏流体的层间组分非均质性、流体流动的瞬态热效应及强烈的运移分异性反映了流体流动的不连续性、流体运移过程中温度、压力条件的快速变化及多期流体的相互作用,可成为幕式流体活动和油气幕式快速成藏的有效识别标志。

关键词: 超压流体, 底辟, 流体流动, 天然气, 晚期快速成藏, 莺歌海盆地