海洋天然气水合物的地球物理研究(III):似海底反射

对天然气水合物研究中与似海底反射有关的一些观点进行讨论 ,以推动天然气水合物地震研究的认识 .30年的似海底反射研究表明 ,似海底反射仍然是指示天然气水合物沉积存在的最好手段之一 .有似海底反射 ,是可以认为存在天然气水合物的 .虽然存在“游离气带速度模型”与“水合物楔速度模型” ,但似海底反射主要由天然气水合物稳定带底界下方的游离气引起 .BSR上方的天然气水合物、下方的游离气与天然气再循环和含甲烷的流体流有关 .由于天然气水合物稳定带计算控制因素难以准确确定等因素 ,似海底反射与天然气水合物稳定带底界只是近似的对应关系 .需从动态的观点考虑天然气水合物 天然气体系及其与似海底反射的关系 .

Geophysical researches on marine gas hydrates(III): bottom simulating reflections

To promote seismic researches on gas hydrate, some viewpoints are discussed about bottom simulating reflections (BSRs). More than 30 years' researches on BSRs show that BSRs are still one of the best indicators of presence of gas hydrate-bearing sediments. If BSRs are found, gas hydrates can be considered to exist. There are two velocity models; one is free gas zone model and the other hydrate wedge model. But BSRs are primarily caused by free gas beneath the base of gas hydrate stability zone (BGHS). Gas hydrates above BSRs and free gas beneath BSRs are related with gas recycling and methane-bearing fluid flux. Due to the difficulty to exactly determine in site controlling factors about gas hydrate stability zone calculation and others, BSRs are approximately corresponding to the BGHS. The relationships between gas hydrate gas system and BSRs should be studied from viewpoints of dynamic evolution.