Study On The Influence Of Reservoir Pore Structure On S-P Wave Velocity In Shaximiao Formation

The seismic wave velocity of sandstone reservoir is affected by many factors,among which rock pore structure is the most important one.For tight sandstone,the relationship between pore diameter and pore path is different from that of high pore sandstone,and the influence of pore structure on P-wave and S-wave velocity is rarely studied.In this paper,aiming at 43 core samples from nine wells of tight sandstone reservoir in Shaximiao formation,using the methods of pore-permeability test and thin slice identification under overburden pressure,the attribute characteristics of sample particles,minerals,porosity and permeability are obtained respectively.The pore structure parameters of the samples are extracted by CT scanning technology,and the P-wave and S-wave velocities under different confining pressures are measured by ultrasonic transmission method.The relationship between transverse and longitudinal wave velocity and porosity and pressure of tight sandstone in Shaximiao formation and the influence of pore structure parameters on velocity are analyzed.The experimental results show that the mineral composition of tight sandstone samples in Shaximiao reservoir is mainly quartz,followed by feldspar,and the cuttings content of most samples is low.The mineral composition contents of samples from different wells are different,and the mineral composition contents of samples from the same well are similar.There are differences in pore structure of different samples,and the pore structure parameters of samples in the same well can be compared.The velocity of the sample increases rapidly at low pressure and slowly at high pressure,and the P-wave and S-wave velocity growth curves of different samples are different.The P-wave and S-wave velocities of samples decrease with the increase of porosity,and the correlation between P-wave velocities and porosity of saturated samples is better than that of dried samples.Under the condition of similar mineral composition and porosity,the smaller the pore aspect ratio,the greater the increase of the pressure velocity of the drying sample;the drying sample speed is affected by the pore radius,and the larger the pore radius is,the smaller the velocity is;the velocity of the saturated sample is affected by the throat radius,and the smaller the throat radius is,the greater the velocity is.