岩石声波压实效应的实验研究

选用不同地区2口井的具有代表性的不同岩性的砂岩、泥岩样品,研究孔隙结构、孔隙流体性质、岩石骨架在声波压实效应过程中所起的作用.研究发现: (1) 纵波时差(Tp)的压实效应随孔隙度(φ)增大而趋明显,孔隙度越大,时差随压力变化越快; (2)随着上覆有效压力(p)的增大,时差与孔隙度的线性相关程度减弱,说明Wyllie时间平均方程在较低压力范围内敏感; (3) 孔隙中所饱和的流体对横波速度(vs)影响不明显,而对于纵波,气饱和样品的波速明显小于液体饱和的波速,且气饱和样品的波速在低压时随压力的变化率比液体饱和的大; (4) 对于砂岩,在泥质含量与颗粒分选一定的情况下,颗粒分选差的岩石其杨氏模量比分选好的岩石大,颗粒分选差的岩石的杨氏模量随压力增大近似呈线性上升,颗粒分选好的岩石呈指数上升趋势;对于砂泥岩,弹性模量随着砂质含量的增大而增大.

Study on Compaction Effect of Rock Sonic Wave

Some samples of sandstone and mudstone from two wells in different areas are selected to investigate the effects of pore structure, pore fluid characters and matrix on the acoustic compaction process. It is found that the compaction of P-wave stepout trends to be clear with the porosity increasing. The bigger the porosity is, the more rapidly the stepout will change with the pressure variations. With the increase of overlying effective pressure ( p ), the linear correlation between stepout and porosity declines, which shows that Wyllie time average equation is sensitive in the low-pressure range. The saturated fluid in the pores doesn't show apparent effect on S-wave velocity. But to P-wave, its velocity in the gas-saturated samples is lower than that in the fluid-saturated samples distinctively. Moreover, when the pressure is low, the changing ratio of P-wave velocity with pressure in the gas-saturated samples is bigger than that in the fluid-saturated samples. To sandstone, on the condition that the clay content and sorting is constant, the Young's modulus of rocks with bad particle sorting is bigger than that of rocks with good sorting. The Young's modulus of rocks with bad particle sorting increases linearly with the increase of pressure, while in rocks with good sorting, it is exponential. To shale-sandstone, the elastic modulus increases with the content of sand increase.