不同因素作用下致密灰岩声波特性和孔压关系研究

灰岩的成岩作用复杂,常规的孔隙压力预测方法不再适用;可以利用灰岩的声波性质和孔压之间的关系来实现孔压的预测。为了探究致密灰岩声波特性和孔压之间的关系,对苏里格气田马五组灰岩岩样进行了声波特性试验,研究了孔隙度、层理、围压和轴压等不同影响因素作用下,灰岩纵横波波速随孔压的变化规律及其产生的原因。实验结果表明,灰岩的孔隙度与渗透率没有特定关系;纵横波波速与孔压的关系呈现规律性变化。当孔压较小时;纵横波波速变化较小,当孔压增大到一定程度后,纵横波波速随孔压的增大而迅速减小,这种现象可以通过有效应力来解释。随着孔隙度的增加,纵横波波速会呈现非线性减小;平行层理方向纵横波波速要大于垂直层理方向,因为平行层理方向声波阻抗小;不同围压和轴压作用下,灰岩纵横波波速随孔压的变化规律相似,并且在孔压较小时,纵横波波速相差不大,当孔压增大到一定程度后,纵横波波速之间差距变大。

Relationship Research Of Dense Limestone Acoustic Characteristics and Pore Pressure Under Different Influencing Factors

The diagenesis of limestone is complex that conventional prediction way of pore pressure is not applicable and relationship of acoustic characteristics and pore pressure can be used to predict pore pressure. To do research of relationship of limestone acoustic characteristic and pore pressure, limestone samples from Mawu formation of Sulige gas field are got to do acoustic experiments which study the relationship of vertical and horizontal wave velocity and pore pressure under different porosity, beddings, confining pressure and axial pressure and the reason. The research shows that, there is close relationship between porosity and composition, but not with the permeability; the relationship between vertical and horizontal wave velocity and porosity is regular, and the vertical and horizontal wave velocity change little with the increase of the pore pressure when the pore pressure is small, but dramatic enough when the porosity pressue is large enough and this can be explained by effective stress; the vertical and horizontal wave