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实验研究了地震波在岩石中的衰减,工作的主要目的在于弄清摩擦滑移和流体流动这两种衰减机制。通过使砂岩棒在500至9000赫芝的频率范围内共振的方法,研究了封闭压力、孔腔压力、饱和度、应变振幅和频率的影响。实验观测到衰减和速度随应变振幅变化,这被解释为颗粒接触处存在摩擦滑移。在地球中地震波传播的应变和封闭压力的典型条件下,这种振幅相关性消失。所以,我们推测摩擦滑移不是在位地震衰减的重要原因。部分水饱和使压缩波(P 波)和剪切波(S 波)的衰减比干岩石显著增加,从而导致 P 波衰减大于 S 波衰减。完全饱和使 S 波衰减达到最大,但引起 P 波衰减减小。这些效应能够借助于波引起孔腔流体的流动来解释,压缩衰减与剪切衰减的比值比起相应的速度比值能更灵敏和更实际地指示气体的部分饱和度,这方面的知识将可能应用于天然气和地热蒸汽资源的勘探。
The attenuation of seismic waves in the rock is experimentally studied. The main purpose of the work is to understand the two kinds of attenuation mechanisms of friction slip and fluid flow. The effects of confining pressure, cavity pressure, saturation, strain amplitude and frequency were studied by resonating sandstone rods in the frequency range of 500 to 9000 Hertz. Experimentally observed attenuation and velocity changes with strain amplitude, which is interpreted as frictional slip at the particle contact. This amplitude dependence disappears under the typical conditions of seismic strain propagation and closure pressure in the earth. Therefore, we speculate that the friction slip is not an important reason for the seismic attenuation in place. Partial water saturation causes the attenuation of compressional (P) and shear (S) waves to increase significantly compared to dry rock, resulting in a greater P wave attenuation than the S wave attenuation. Full saturation causes the S-wave attenuation to be maximal, but causes the P-wave attenuation to decrease. These effects can be explained by means of the wave-induced flow of the fluid in the borehole. The ratio of compression attenuation to shear attenuation can be more sensitive and practical to indicate the partial saturation of the gas than the corresponding speed ratio, and this knowledge will probably be applied to Exploration of Natural Gas and Geothermal Steam Resources.