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研究金属套管对低频电磁场各分量透射信号和反射信号的影响规律对采用过套管电磁感应测井技术监测生产过程中的流体移动具有重要价值.采用柱状成层各向异性介质中的并矢Green函数模拟当发射源在套管内、接收器分别在套管内和套管外时多分量电磁感应的响应,并系统分析了金属套管对透射磁场和反射磁场各主分量的影响规律.计算结果表明,无论是透射场还是反射场,由于所采用的频率较低,金属套管对每个分量信号的影响可以与地层对该分量信号的影响分开.在低频段,磁性金属套管对磁场各分量仍存在稳定的反射,但不同分量被反射的程度不同,受套管磁屏蔽作用大的分量(如ρρ分量)被反射的程度高于受套管磁屏蔽作用小的分量(如zz分量).随着频率的升高,反射磁场的强度逐渐增大并最终达到饱和,信号被全反射.磁性金属套管的存在导致透射磁场各分量出现不同程度的幅度衰减和相位延迟,受套管磁屏蔽作用大的分量的幅度衰减程度大.在固定套管参数和频率的情况下,磁性套管对透射磁场不同分量的影响程度虽然不同但是恒定,其所导致的各分量的幅度衰减和相位延迟与线圈系位置和地层电参数无关.在低频段,套管外透射场的各分量处于准静态,其幅度和相位均不随频率而改变,受套管磁屏蔽作用大的分量的幅度随套管磁导率和厚度的不同而存在明显变化.当频率超过某一临界值后,套管的影响逐渐从以静态屏蔽为主转到以趋肤效应为主,导致透射场幅度的衰减和相位的延迟,套管的厚度越大、套管的电导率和相对磁导率值越大,所对应的频率临界值越小. 相似文献
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通过结合保色散关系空间差分格式和Runge-Kutta时间格式的数值方法,研究了耗散作用对声波传播的影响.结果表明,耗散的不均匀性会同时影响声波的传播轨迹和传输损耗.不均匀的耗散会使得波包上部和下部承受不同程度的衰减,造成波包能量中心向弱耗散方向移动,使波包能量中心的传播轨迹发生偏折.与此同时,声波的传输损耗也受到了改变：与无耗散情况相比,声波的几何扩散衰减受到抑制;与均一耗散情况相比,声波的大气声吸收明显减小.由于声波衰减系数与声波频率的平方成正比,耗散作用使声波传播具有色散性质.不均匀耗散对于声波波包能量中心传播轨迹的偏折作用随频率的增加而增强. 相似文献
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深入了解不同压力、频率、流体含量和流体分布对岩石中弹性波传播特性的影响,对指导油气勘探开发具有重要意义.不同尺度下的波致流效应,是声波传播过程中产生速度频散和衰减的重要原因.本文以不同压力下水饱和区域改进的骨架模量为纽带,建立了联合介观尺度斑块饱和效应与微观尺度喷射流效应的部分饱和岩石声学理论模型.开展针对性声学实验,根据不同压力下部分饱和砂岩纵波速度测量数据,确定理论模型中的相关参数,从而实现对不同压力下部分饱和岩石纵波衰减的定量表征.在此基础上,通过理论与实验测量的纵波衰减的对比,分析不同压力、含水饱和度以及频率对岩石纵波衰减的影响.研究结果表明,在较低压力,较高含水饱和度以及较高频段,喷射流效应较强,因此新建模型计算的衰减明显大于斑块饱和模型的衰减.由于新建模型体现了斑块饱和效应与喷射流效应的综合影响,相比于斑块饱和模型,新建模型计算的部分饱和岩石的纵波衰减更接近于实测衰减,但受到岩石自身因素影响,新建模型计算的衰减仍略小于实测衰减. 相似文献
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从声波在岩体中传播产生衰减的基本原理出发，建立了声波衰减振子的线列阵模型。该模型是将传播声波路径的岩体分为若干个振子，从波动概念出发，以振动原理作依据建立波动方程．为探讨岩体声波衰减机制提供了一种新的研究方法，把振动和波动直观地联系起来．单一方向上有限点的声波测试技术有可能被多方向的声测技术所代替．该模型的建立，使模态分析和参数识别方法应用到岩体声波测试技术中成为可能。 相似文献
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墨西哥湾GC955H井钻遇两种不同的水合物储层,浅层裂隙充填型水合物和深层砂岩型水合物.浅层水合物充填在细粒泥质沉积物的裂隙中,由电阻率测井计算的饱和度平均值为25%.深层水合物充填在砂岩孔隙中,由电阻率计算的饱和度平均为65%.基于声波全波形数据,本文计算了GC955H井储层的声波衰减大小,结果发现两种水合物层对声波衰减的影响不同.泥岩水合物层中的声波衰减与上覆背景泥岩沉积层基本相当.砂岩水合物层的声波衰减大于0.1,最大0.15,远高于上覆和下伏的背景砂岩层.对声波频率的分析发现,GC955H井泥岩层中水合物对声波频率的影响不大,砂岩水合物层的声波频谱与上下背景砂岩层相比发生变化,主频增大.通过对比两种水合物储层的特征,本文初步定性分析了造成水合物对储层声波传播影响不同的原因,包括岩性、水合物饱和度、水合物赋存方式等;但对此的定量描述需要未来更详尽地讨论和研究水合物的声波衰减机制. 相似文献
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地震波在含裂隙岩石内传播时，很大程度上会受到裂隙系统与其内的流体所影响.本文在Chapman提出的频变各向异性理论的基础上，研究气水两相流体受频率影响的程度.不同于许多局限于单一流体假设的频变各向异性理论研究，本文着重于两相流体部分饱和的情况.因此计算频变各向异性弹性常数尤为重要，本文考虑了气水两相的相对渗透率对横波速度及其衰减的影响，并引入了基于分形理论的相对渗透率模型.首先研究在不同分形维数的情况下，气水两相相对渗透率随含水饱和度的变化趋势，并且随着该变化对有效流体迁移率的影响.气体的相对渗透率与分形维数成正比例关系，而水的相对渗透率与分形维数成反比例关系.随后根据数值算例计算双相不混溶流体饱和裂隙岩石频变各向异性弹性模量的方程，得到横波速度及横波衰减，对比分析相对渗透率及分形维数的变化对横波速度和横波衰减的影响．根据算例结果可知，在不同频率下，相对渗透率对横波速度和横波衰减的影响程度不同，在中频时最大．引入不同的相对渗透率模型，能在中频时观察到其对横波速度和衰减的不同影响． 相似文献
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研究地震波在含黏性流体孔隙介质中的传播特性,对于识别油气储层、刻画流体边界、判识油水界面等有重要作用.通常利用地震波在孔隙介质分界面上的反透射系数特征,来实现这些方面的研究.顶、底层孔隙介质之间存在含黏性流体孔隙介质夹层时,夹层内岩石骨架、孔隙因子、孔隙流体等参数会对反透射系数产生影响.本文推导出含夹层孔隙介质分界面上的反透射系数方程,针对方程建立不同孔隙度的含夹层孔隙介质模型;基于模型实现孔隙介质分界面上的反透射系数特征研究,分别分析不同夹层厚度、不同频率情况下,反透射系数随入射角的变化规律.研究表明,快慢纵波及横波的反透射系数都会受到孔隙夹层的影响,受影响程度主要取决于夹层厚度和地质背景等因素;慢纵波反射和透射系数数值极小,且后者随夹层厚度的增加而迅速衰减;频率通过反透射系数方程本身和地震波速度两个因素直接或间接的影响地震波反透射特征,其值的增加会引起快纵波和横波反透射系数不同程度的衰减. 相似文献
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In the present article, the dependencies of the acoustic signal total energy and the energies of the wave packets of different types of the waves on the elastic parameters and permeability of rocks have been studied. We have considered traditional logging tools containing acoustical monopole source. Calculations were performed in a frequency range of dozens of kilohertz, typical for acoustic well logging. It was shown that in a typical high-velocity formation (vs > vf, where vs and vf are the velocities of the shear wave in the rock and of the compressional wave in the borehole fluid, respectively), the pseudo-Rayleigh waves, whose elastic properties depend mainly on the shear modulus of the rock, contributed significant energy to the total signal energy in the borehole. The energies of different wave packets depend on the permeability in different ways. The greatest sensitivity to permeability change has been shown by the acoustic signal total energy and the energy of the low-velocity part of the pseudo-Rayleigh wave packet. The theoretical analysis was illustrated by real sonic log data. 相似文献
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EXPERIMENTAL STUDY ON THE CHANGES OF ULTRASONIC CODA WAVE AND ACOUSTIC EMISSION DURING ROCK LOADING AND DEFORMATION 
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下载免费PDF全文 YANG Hai-ming CHEN Shun-yun LIU Pei-xun GUO Yan-shuang ZHUO Yan-qun QI Wen-bo 《地震地质》1979,42(3):715-731
The coda wave propagation path has received extensive attention as it is more sensitive to small changes in the medium than the direct wave. During the process of loading, the wave velocity, medium or source changes may cause the coda wave to change. The physical mechanism of change in the ultrasonic coda wave varies during different deformation stages. Meanwhile, there exist local damages in the rock sample during the deformation, and it will be accompanied by acoustic emission. Combining the ultrasonic coda wave and acoustic emission is beneficial to characterize the coda wave characteristics and damage degree of the sample at different deformation stages. In this paper, three kinds of rocks, including granodiorite, marble and sandstone with the sizes of 50mm×50mm×150mm, are used to carry out observations of ultrasonic coda wave and acoustic emission during the whole process of loading so as to study characteristics of the coda wave at different deformation stages. The major results are given below: 1)There is a good correspondence between the coda wave variation and the acoustic emission evolution process. When the acoustic emission frequency increases, the coda wave changes accordingly. In particular, the coda wave changes in the early stages of increased acoustic emission frequency, which indicates that the early damage information of rock can be obtained by analysis of the coda wave. 2)The physical mechanism of the coda wave change is different in different deformation stages. At the initial stage of loading, there are obvious scatterer changes in the coda wave change; then, in the linear elastic deformation stage, the wave velocity change is dominating; in the late-stage of loading, the scatterer change increases and coexists with the wave velocity change, the scatterer change effect is related with the rock micro-fracture degree, the rock will locally be damaged before rupturing, and the role of the scatterer will be enhanced. 3)With the increase of loading, the amplitude of increase of the wave velocity generally decreases gradually, which is basically consistent with the understanding obtained through the direct wave. The interference of acoustic emission can be eliminated because of the Kaiser effect when analyzing the coda wave. The consistency of the wave velocity change and stress loading and unloading is further verified. 4)The micro-fracture generated during rock deformation will change the physical mechanism of the coda wave change, and the scatterer effect will be significantly enhanced. At the same time, the acoustic emission waveform will cause interference to the ultrasonic coda wave. This means that attention needs to be paid when analyzing rock damage using only coda wave data. In short, the ultrasonic coda wave and acoustic emission can reflect the damage inside the rock, and the change mechanism of the coda wave in different deformation stages is different. The joint observation of the two can play a mutual verification role, which is conducive to improving the reliability of the observation results. 相似文献
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利用新方法制作出含可控裂缝的双孔隙人工砂岩物理模型,具有与天然岩石更为接近的矿物成分、孔隙结构和胶结方式,其中裂缝密度、裂缝尺寸和裂缝张开度等裂缝参数可以控制以得到实验所需要的裂缝参数,岩样具有真实的孔隙和裂缝空间并可以在不同饱和流体状态下研究流体性质对于裂缝介质性质的影响.本次实验制作出一组具有不同裂缝密度的含裂缝人工岩样,对岩样利用SEM扫描电镜分析可以看到真实的孔隙结构和符合我们要求的裂缝参数,岩样被加工成八面棱柱以测量不同方向上弹性波传播的速度,用0.5 MHz的换能器使用透射法测量在饱和空气和饱和水条件下各个样品不同方向上的纵横波速度,并得出纵横波速度、横波分裂系数和纵横波各向异性强度受裂缝密度和饱和流体的影响.研究发现流体对于纵波速度和纵波各向异性强度的影响较强,而横波速度、横波分裂系数和横波各向异性强度受饱和流体的影响不大,但是对裂缝密度的变化更敏感. 相似文献
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准确预测煤岩破裂震源方位,确定采掘工作面重点灾害区域,可以使煤岩动力灾害防治措施更为有效.根据煤岩变形破裂电磁效应规律和电磁波基础理论,提出了一种利用电磁信号能量来确定局部震源方位的方法,并通过实验室定向接收实验和平煤十矿现场测试验证该方法的有效性.结果表明,电磁信号强度随着煤岩体应力状态变化而变化;两个正交天线接收的电磁信号能量分别与各自接收夹角余弦值的平方成正比,利用此比例关系可以确定震源的方位;电磁信号定位方法与静态指标法预测局部区域危险性具有较好的检验一致性.研究成果为煤岩动力灾害重点灾害区域的判定提供依据. 相似文献
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Wave‐induced fluid flow plays an important role in affecting the seismic dispersion and attenuation of fractured porous rocks. While numerous theoretical models have been proposed for the seismic dispersion and attenuation in fractured porous rocks, most of them neglect the wave‐induced fluid flow resulting from the background anisotropy (e.g. the interlayer fluid flow between different layers) that can be normal in real reservoirs. Here, according to the theories of poroelasticity, we present an approach to study the frequency‐dependent seismic properties of more realistic and complicated rocks, i.e. horizontally and periodically layered porous rock with horizontal and randomly orienting fractures, respectively, distributed in one of the two periodical layers. The approach accounts for the dual effects of the wave‐induced fluid flow between the fractures and the background pores and between different layers (the interlayer fluid flow). Because C33 (i.e., the modulus of the normally incident P‐wave) is directly related to the P‐wave velocity widely measured in the seismic exploration, and its comprehensive dispersion and attenuation are found to be most significant, we study mainly the effects of fracture properties and the stiffness contrast between the different layers on the seismic dispersion and attenuation of C33. The results show that the increasing stiffness contrast enhances the interlayer fluid flow of the layered porous rocks with both horizontal and randomly orienting fractures and weakens the wave‐induced fluid flow between the fractures and the background pores, especially for the layered porous rock with horizontal fractures. The modelling results also demonstrate that for the considered rock construction, the increasing fracture density reduces the interlayer fluid flow while improves the dispersion and attenuation in the fracture‐relevant frequency band. Increasing fracture aspect ratio is found to reduce the dispersion and attenuation in the fracture‐relevant frequency band only, especially for the layered porous rock with horizontal fractures. 相似文献
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在油、气储层的勘探和开发中观察到的一个现象是储层岩石中普遍存在孔隙和裂隙.随着近年来孔、裂隙介质弹性波动理论的进展,我们可以将此理论应用于测井技术,以此来指导从声波测井中测量孔、裂隙地层的声学参数.本文计算了孔、裂隙地层里充流体井眼中的多极子声场,分析了声场随裂隙介质的两个主要参数(即裂隙密度和裂隙纵横比)的变化特征.井孔声场的数值计算表明裂隙密度可以大幅度地降低井中声波纵、横波的波速和振幅.随着裂隙密度的增加,在测井频段内也可以看到纵、横波速的频散现象(这种频散在孔隙地层中一般是观察不到的).本文还研究了多极子模式波 (即单极的Stoneley波、伪瑞利波以及偶极的弯曲波)随裂隙参数的变化特征.结果表明,这些模式波的振幅激发和速度频散都受裂隙密度的影响.裂隙密度越高影响越大.此外,裂隙还对模式波的传播造成较大的衰减.相对裂隙密度而言,裂隙纵横比是一个频率控制参数,它控制裂隙对声场影响的频率区间.本文的分析结果对裂缝、孔隙型地层的声波测井具有指导意义. 相似文献
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Partially saturated reservoirs are one of the major sources of seismic wave attenuation, modulus defect and velocity dispersion in real seismic data. The main attenuation and dispersion phenomenon is wave induced fluid flow due to the heterogeneity in pore fluids or porous rock. The identification of pore fluid type, saturation and distribution pattern within the pore space is of great significance as several seismic and petrophysical properties of porous rocks are largely affected by fluid type, saturation and fluid distribution pattern. Based on Gassmann-Wood and Gassmann- Hill rock physics models modulus defect, velocity dispersion and attenuation in Jurassic siliclastic partially-saturated rocks are studied. For this purpose two saturation patterns - uniform and patchy - are considered within the pore spaces in two frequency regimes i.e., lower frequency and higher frequency. The results reveal that at low enough frequency where saturation of liquid and gas is uniform, the seismic velocity and bulk modulus are lower than at higher frequency where saturation of fluid mixture is in the form of patches. The velocity dispersion and attenuation is also modeled at different levels of gas saturation. It is found that the maximum attenuation and velocity dispersion is at low gas saturation. Therefore, the dispersion and attenuation can provide a potential way to predict gas saturation and can be used as a property to differentiate low from high gas saturation. 相似文献
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The evidence attesting to the possibility of the largest spectral maximum in seismic noise with a peak frequency of 0.14–0.22 Hz to form as a result of low-frequency dissipation of elastic wave energy in rocks is presented. According to this mechanism, elastic wave energy in rock, which can be considered as a two-component medium (solid matrix + pore water), is dissipated in the form of low-frequency pulses whose energy is the lower the smaller the coefficient of porosity. It is assumed that weak seismic events continuously occur in the frequency range above 6 Hz, and their dissipated energy is a source of the low-frequency noise. 相似文献
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理论计算及实测资料表明,反射波法基桩动测激振信号近似为半周期正弦波,不同激振方式产生的桩顶速度脉冲信号宽度不同,相应频率成分也就不同。桩身内阻尼对不同频率谐波的幅值衰减及频散规律不同,使得不同激振方式产生的复合脉冲在同一桩中会有不同变化规律,为了使不同激振方式测试资料具有可比性,应采用相同频带进行对比。为此利用小波分析的时-频特性,通过对测试信号进行时频分解,就桩身内阻尼对不同频带信号的吸收系数及波速的影响规律进行了研究。对实测资料分析的结果表明,预制桩不同频带信号波速变化不大,但衰减系数随频率增大近似线性增加。 相似文献
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核磁共振测井在火成岩地层应用的适应性分析 总被引：1，自引：0，他引：1
火成岩岩石具有高磁化率特征,与沉积岩差别明显,岩石的高磁化率会对核磁共振信号产生显著影响,开展核磁共振测井在火成岩地层应用的适应性分析研究,为广泛使用核磁共振测井用于火成岩储层评价提供参考.采用理论模拟、实验分析及实际测井资料相结合的方法,分析了高磁化率岩石的核磁共振响应特征.分析结果表明,火成岩岩石具有很高的磁化率,从酸性火成岩到基性火城岩,岩石的磁化率一般是逐渐增大的.高磁化率岩石孔隙内部会产生强梯度磁场,孔隙内部的磁场梯度越强,核磁共振的T2谱前移越明显,核磁信号衰减幅度也越大,核磁分析孔隙度与常规分析的孔隙度误差也越大;相同岩石磁化率情况下,岩石孔径越小,岩石孔隙内部磁场梯度越强,核磁信号衰减越大,核磁共振测井计算的孔隙度也越低.因此,核磁共振测井与岩性有关系,核磁共振测井会受到高磁化率岩石的显著影响.核磁共振测井在部分火成岩,尤其在中基性火成岩和小孔径火成岩储层中应用具有很大的局限性. 相似文献