基于三维孔隙网络模型的纵波频散衰减特征分析  

Attenuation and dispersion characteristics of P-waves based on the three-dimensional pore network model

作　　者：魏乐乐 甘利灯[1] 熊繁升 孙卫涛 丁骞 杨昊[1] WEI LeLe;GAN LiDeng;XIONG FanSheng;SUN WeiTao;DING Qian;YANG Hao(Geophysical Department,RIPED,PetroChina,Beijing 100083,China;Zhou Pei-Yuan Center for Applied Mathematics,Tsinghua University,Beijing 100084,China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]清华大学周培源应用数学研究中心,北京100084

出　　处：《地球物理学报》2021年第12期4618-4628,共11页Chinese Journal of Geophysics

基　　金：中国石油天然气股份有限公司勘探工程技术研究与应用项目(kt2018-10-02);中国石油天然气股份有限公司科技项目(kt2021-12-02)资助.

摘　　要：波场在含流体的孔隙介质中传播时会产生频散和衰减现象.波场的频散和衰减与孔隙介质的岩石物理属性有关,包括孔隙度、渗透率、流体属性等.现有的三维裂缝/软孔隙网络模型利用椭圆截面纵横比的变化模拟从扁裂缝、软孔隙到硬孔隙的多种情况,而未考虑同时包含孔隙和裂缝的全局性网络空间.为了更好地描述裂缝-孔隙空间,本文提出同时包含裂缝和孔隙的三维裂缝孔隙网络模型,并给出渗透率的计算方法.通过体积平均法推导了三维裂缝/软孔隙网络模型和三维裂缝-孔隙网络模型的波动方程,利用平面波分析方法得到纵波频散/衰减曲线的表达式,同时应用数值模拟研究了总孔隙度、裂缝孔隙度、裂缝纵横比、裂缝数密度、孔隙流体黏度对纵波衰减和速度频散特征的影响.结果表明,在三维裂缝-孔隙网络模型下,总孔隙度、裂缝参数等对纵波频散衰减特征的影响与三维裂缝/软孔隙网络模型相似.具体表现为:纵波在高频段内出现频散和衰减现象.孔隙度的变化主要影响逆品质因子曲线峰值的大小;裂缝数密度主要控制速度显著变化的范围;裂缝纵横比对纵波速度和特征频率有显著影响.When propagating in a porous medium containing fluid,the wave field will undergo dispersion and attenuation.Such phenomena are related to the petrophysical properties of the porous medium,including porosity,permeability,fluid properties and so forth.In previous work,based on the three-dimensional fracture/soft pore network model,the variation of the aspect ratio of the ellipse section is used to simulate a variety of conditions from flat fractures to soft pores to hard pores,but does not consider the global network space containing both pores and fractures.To better describe the fracture-pore space,we propose three-dimensional fracture-pore network and the method to calculate the permeability.Through volume averaging,we derive the wave equations of these two three-dimensional pore network models.Then,the expressions of dispersion/attenuation curves of P-waves are obtained by plane wave analysis.And by using numerical simulation,many influence factors are analyzed for the attenuation and dispersion of P-waves,such as total porosity,fracture porosity,fracture aspect ratio,fracture density and pore fluid viscosity.Results show that based on the 3D fracture-pore network model,the effects of total porosity and fracture parameters on the dispersion/attenuation of fast P-waves and the dispersion/attenuation trend of slow P-waves are similar to those of the 3D fracture/soft pore network model.Specifically,the attenuation and dispersion of fast P-waves occur in high-frequency bands.The change of porosity mainly affects the peak value of inverse quality factor curve.The fracture density mainly controls the range of significant change in velocity.And the fracture aspect ratio has a significant effect on the P-wave velocity and characteristic frequency.

关 键 词：三维裂缝/软孔隙网络模型 三维裂缝-孔隙网络模型 波动方程 频散衰减 

分 类 号：P631[天文地球—地质矿产勘探]