陆域天然气水合物储藏的裂隙模型及其地震波传播特性

Crack model of natural gas hydrate reservoir in continental permafrost and its characteristics on seismic wave propagation

陆域天然气水合物是可持续发展的清洁能源,其勘探、开发及应用前景广阔。目前,陆域天然气水合物的地震勘探特征尚不明晰。这里从岩石物理模型出发,针对实验以及测井数据进行研究,发现天然气水合物赋存层段和围岩均与裂隙发育密切相关,研究了地震波在不同裂隙介质中的传播规律。结果表明,当裂隙中流体处于连通状态时,其地震波速度受频率影响显著。根据冻土带特点,这里建立了水合物赋存层段和围岩分别含裂隙的储藏模型,研究其地震勘探频率和振幅随偏移距变化(AVO)特点。与实际地震勘探响应的对比表明,流体通过裂隙相互连通的裂隙模型符合冻土带天然气水合物的储藏特点。上述裂隙模型及其地震波传播特性为冻土带天然气水合物的成藏机制提供了新地认识,为合理勘探开发我国陆域天然气水合物资源提供了借鉴。

Natural gas hydrate in continental permafrost is a sustainable and clean energy source,and its exploration,development and application are promising.Experimental data and logging response based on rock-physics are studied in this paper.It is found that the occurrence of gas hydrate is closely related to cracks.Therefore,the propagation of seismic wave through different crack models are studied.The results show that when the fluid in cracks is connected,the seismic wave velocity is significantly affected by the frequency.According to the features of permafrost-sediments,the reservoir models with cracks in hydrate-bearing zones and surrounding sediments separately are established to reveal the characteristics of exploration-frequency and amplitude versus offset(AVO).Comparing with seismic exploration response,it shows that the crack model with fluid passing through cracks fits well with the reservoir-features of natural gas hydrate.Above all,the crack model and its characteristics on seismic wave propagation provides some new knowledge on the accumulation mechanism of hydrate reservoir,and it may provide theoretical proof for the exploration and development of natural gas hydrate resources in China.