孔隙流体分布对部分饱和储层砂岩速度实验结果的影响及理论分析

The effects of pore fluid distribution to the experimental velocity of partially saturated reservoir sandstones.

在实验室高频条件下,对储层砂岩样品采用常规吸入饱和法得到的纵波速度与饱和度的相关性表现出复杂的变化趋势,在压力较低时纵波速度随饱和度的增加表现出非线性增大,而压力较高时纵波速度先减小后增加,实验结果与地震勘探中用有效流体模型得到的理论值不同。对基于有效流体模型和斑块模型的弹性波速度与饱和度的相关性理论进行了讨论,指出不均匀斑块饱和方式对速度的影响是频率相关的,它包含了多个孔隙的一种更大尺度上的频散作用。对低压力下的部分饱和储层砂岩样品的速度实验值进行了Biot流和喷射流频散作用校正,实验所得的纵波速度值落在了有效流体模型的下限速度值斑块模型和上限速度值所围成的区域内。

The condition of high frequency at the experimental, the saturation dependence of the P-wave velocity in reservoir sandstone samples put up complex variation tendency when adopting conventional imbibitions saturation methods. Under the low confining pressure, P-wave velocity show non-linear increase with increasing water saturation; under the high confining pressure.P-wave velocity first decrease with increasing water saturation, and then increase with increasing water saturation after certain saturation, which are different from the theoretical results of effective fluid model commonly used in seismic exploration.The saturation dependence of elastic velocity based on effective fluid model and patchy saturation model was discussed elaborately, and some important conclusions have been draw. The effects of patchy saturation on compression wave velocity depend on frequency, which is also another kind of dispersion mechanism at much larger scales than any pore. After velocity calibration to eliminate the effects of Biot flow and squirt fluid, experimental velocity results of partially saturated rock samples are all in the region bounded by the predicted results of effective fluid model and patchy saturation model under low confining pressure.