致密砂岩声波速度试验研究及其应用

A Study of Tight Sandstone Acoustic Velocity Experiment and Its Application in Well Logging

由于塔里木盆地研究工区致密砂岩储层具有低孔低渗、微裂隙、裂缝发育和非均质性强的特点，导致该区致密砂岩气层识别困难。针对该难题，根据声波在岩石中的传播特性，以钻井取心的小岩样为对象，研究了在一定压力下声波速度随流体饱和度的变化规律，即随着含气饱和度的增加，纵波速度在含气饱和度20Voo～70％范围内明显减小，而且随着物性（孔隙度（击）、渗透率（K））的变好，纵波速度的变化也越大；而横波速度几乎保持为一个常量或略有减小。在充分考虑物性的条件下，提出了用纵横波速度比识别气层的方法。该方法在研究区的实际应用中取得了较好的效果。

The tight sandstone reservoirs in Tarim Basin had the characteristics of low porosity,low permeability,micro-fractures,fracture development and strong heterogeneity,which caused the difficulty for tight sandstone gas reservoir recognition in the region.In view of this problem,according to the acoustic propagation characteristics in rocks,small rock samples of drilling coring are used as an object to study the law of the acoustic velocity changing with fluid saturation under a certain pressure,with the increase of gas saturation,longitudinal wave velocity obviously decreases at the gas saturation of 20% ~70%,and with the increase of physical property(porosity()and permeability(K)),the change of the longitudinal wave velocity is the greater,the shear wave velocity is almost as a constant or slightly decreases.Under the condition of fully considering the physical property,a method of p-wave-to-s-wave ratio is proposed for gas identification.The method is used in the researched area and good effect is achieved in actual application.