低孔隙度低渗透率砂岩的声波特性实验研究

用实验方法探讨了气驱水过程中低孔隙度低渗透率砂岩的纵横波速度、纵横波速比、弹性模量等参数随不同含气饱和度的变化;同时在频率域内探讨了纵横波的主频、带宽、品质因素Q随不同含气饱和度的变化.实验表明,10%～20%的气体可使低孔隙度低渗透率砂岩岩心的纵波速度、纵横波速比迅速下降;而低孔隙度低渗透率岩心的纵波主频、带宽、品质因素Q也与含气饱和度有明显的关系,10%～20%的气体可使其纵波主频、带宽及Q值显著下降,这种降低的趋势比纵波速度、纵横波速比更急剧更敏感.用纵波主频、带宽、品质因素Q比用纵波速度和纵横波速比更能反映低孔隙度低渗透率岩层是否含气体.

Experiments on Acoustic Characters of Low Porous and Permeable Sandstones

Studied are changes of compressional wave velocity(v p) and shear wave velocity(v s ),v p/v s ratio and elastic moduli of low porous and permeable sandstone cores with the changes of gas saturation during gas driving water. At the same time, the changes of main frequency, frequency band and quality factor with the variations of gas saturation are analyzed. The experiments show that 10 to 20 percent of gas makes the v p and v p/v s ratio drop quickly in the sandstones. For the cores, there is evident relation between compressional main frequency, frequency band, quality factor and gas saturation; 10 to 20 percent of gas can make the compressional main frequency ,frequency band , quality factor drop obviously. This downward tendency is stronger than that of the v p and v p/v s ratio . Compressional main frequency ,frequency band and quality factor are much better than v p and v p/v s ratio in identifying the presence or absence of gas in the sandstones.