基于孔隙纵横比谱反演的饱和岩石宽频段岩石物理模型  

Multi-frequency band rock physics model for saturated rock based on pore aspect ratio spectral inversion

作　　者：韩旭 王尚旭[1] 刘浩杰 刘韬[3] 唐跟阳 HAN Xu;WANG Shangxu;LIU Haojie;LIU Tao;TANG Genyang(School of Geophysics,China University of Petroleum-Beijing,Beijing 102249,China;Sinopec Shengli Oilfield Geophysical Research Institute,Shandong 257000,China;Sinopec Exploration and Development Research Institute,Beijing 100728,China)

机构地区：[1]中国石油大学(北京)地球物理学院,北京102249 [2]中国石化胜利油田物探研究院,山东257000 [3]中国石化石油勘探开发研究院,北京100728

出　　处：《石油科学通报》2022年第3期334-342,共9页Petroleum Science Bulletin

基　　金：国家自然科学基金(NSFC)深部油气资源积累和关键工程技术基础研究项目(U19B6003);国家自然科学基金(41930425);中国石油大学(北京)科学基金(2462020YXZZ08)联合资助。

摘　　要：对于常规砂岩,速度主要受孔隙度、矿物成分和孔隙流体控制。然而,实验测量结果表明,岩石的孔隙结构同样是岩石的弹性参数的主要控制因素之一。岩石微观孔隙结构特征不仅影响岩石的弹性参数,也决定了流体饱和岩石中流体流动造成的频散与衰减效应。Gassmann理论模型忽略微观孔隙结构影响,往往不能解释岩石弹性性质的压力和频率依赖性,本文则对K-T模型进行扩展来表征压力对流体饱和岩石的弹性模量的影响,在此基础上,将喷射流模型计算的频变流体体积模量带入到K-T模型中建立岩石的频率依赖性。首先,基于速度-压力变化曲线与孔隙结构参数的函数关系,利用实测超声速度数据来反演孔隙纵横比分布及其孔隙度(即孔隙纵横比谱);其次,将干燥硬孔隙加入岩石基质,基于K-T等效介质模型计算岩石干骨架弹性模量,并带入流体频变体积模量,计算加入饱和软孔隙后的岩石“干骨架”的弹性模量;最后利用Gassmann流体替换理论计算硬孔隙中饱和流体的弹性模量。为了验证模型的准确性,对一块饱油致密砂岩样进行超声速度测量并与该模型预测结果相对比,结果表明相比于Gassmann模型,新模型能更好的解释测量结果,且能预测饱和岩石的速度的压力和频率依赖性。实际测量和建模结果表明,压力和频率的影响是耦合的,因为它们通过孔隙的微观结构相互连接。该模型不需要多余的拟合参数,所有参数均由实验室测量和推导,提高了理论建模的准确性。改进模型可用于描述饱和岩石宽频带内弹性频散和衰减,如果能通过地震数据反演获得干燥和饱和状态的弹性模量,则该模型可用于提取岩石孔隙微观结构和流体特性。In conventional sandstone, the velocity is primarily controlled by porosity, mineral composition and pore fluids. However, experimental measurements show that the pore structure of the rock is also one of the main controlling factors of the elastic parameters of rocks. The microscopic pore structure characteristics of rocks not only affect the elastic parameters of rocks, but also determine the dispersion and attenuation effects caused by fluid flow in fluid-saturated rocks. The Gassmann theoretical model ignores the influence of microscopic pore structure and often cannot explain the pressure and frequency dependence of rock elastic properties. In this paper, the Kuster–Toks?z(K-T) model is extended to characterize the influence of pressure on the elastic modulus of fluid-saturated rocks. On this basis, the frequency-dependent fluid bulk modulus calculated by the squirt flow model is brought into the K-T model to establish the frequency dependence of the rock. First, based on the functional relationship between the velocity-pressure curve and the pore structure parameters, the measured ultrasonic velocity data is used to invert the pore aspect ratio distribution and its porosity(i.e., the pore aspect ratio spectrum);secondly, dry stiff pores are added to the rock matrix, Based on the K-T effect medium model, the elastic modulus of the dry skeleton of the rock is calculated, and the fluid frequency-dependent bulk modulus is introduced to calculate the elastic modulus of the rock "dry skeleton" after adding saturated soft pores. Finally, the elastic modulus of saturated fluid in stiff pores is calculated by using Gassmann fluid replacement theory. In order to verify the accuracy of the model, ultrasonic velocity measurement was carried out on an oil-saturated tight sandstone sample and compared with the prediction results of the model. The results show that compared with the Gassmann model, the new model can better explain the measurement results and predict the pressure and frequency dependence of the velocity

关 键 词：孔隙结构 速度频散 声学特性 岩石物理模型 

分 类 号：P618.13[天文地球—矿床学]