储层地震物理模拟的震源指向性及介质非均质性影响分析

随着地震物理模拟的研究目标由地质构造发展为不同类型的油气储层,明确震源指向性及介质非均质性对实验结果的影响,对提高物理模拟数据的可信性及准确性具有重要意义.利用激光测振新方法对震源指向性进行了实验测试,得到了更加精确的指向性结果,形成了模拟数据振幅补偿方法.制作了具有不同尺度特征的非均质样品,在50 kHz至1000 kHz超声频段下对纵波速度及能量进行了测试,明确了不同的波长/介质尺度比(λ/a)范围内纵波速度及干扰波与有效波能量比的变化特征.结果表明,在地震物理模拟超声频段下射线速度向散射速度的转折点出现在λ/a≈2处;散射速度向等效介质速度的转折点出现在λ/a≈100处.当满足λ/a>200条件时,干扰波与有效波能量比小于5%时,可认为满足储层模拟的等效介质条件.

Influence of source directivity and medium heterogeneity on seismic physical simulation of reservoirs

With the research goal of seismic physical simulation developing from geological structures into different types of oil and gas reservoirs,clarifying the influence of source directivity and media heterogeneity on experiment result is of great significance to improve the credibility and accuracy of physical simulation data.The directivity of the source is tested by using the laser vibration measurement method,more accurate directivity result is obtained and the simulated data amplitude compensation method is formed.The inhomogeneous samples with different scale characteristics are made.The variation characteristics of the velocity and energy of the longitudinal wave are measured and summarized in the ultrasonic frequency band of 50 kHz to 1000 kHz.The variation characteristics of P-wave velocity and the energy ratio of interference wave and effective wave in different wavelength/medium scale ratio(λ/a)are defined.In the physical simulation ultrasonic frequency band,the turning point of ray velocity to scattering velocity appears atλ/a≈2;the turning point of scattering velocity to equivalent medium velocity appears atλ/a≈100.Whenλ/a>200 and the energy ratio of interference wave to effective wave is less than 5%,the equivalent medium condition of reservoir simulation can be satisfied.