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题名	不相混气液饱和孔隙介质声场数值模拟与应用研究
作者	赵海波
学位类别	博士
答辩日期	2007-06-11
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	不相混流体 孔隙介质 声波 有限差分 井间层析成像
其他题名	Numerical study of acoustic wavefield in porous media saturated with two immiscible fluids and its application
学位专业	声学
中文摘要	当油田进入开发中后期时，还有超过一半的油气尚未开采出。挖潜剩余油气，提高油气采收率，是一项意义重大且涉及内容广泛的研究课题。要做好剩余油气挖潜，就必需查明储层中油、气、水动态分布。另外，动态监测CO2封存情况，也需清楚地下储层中的流体分布状况。因此，建立更加符合实际的油气储层声学模型，深入研究油气储层中声波传播的特点，探索描绘储层孔隙流体分布的声波方法，都具有重要意义。 本文针对两种不相混流体饱和的孔隙介质中的声学问题进行了较深入的理论分析和数值模拟研究。此外，井间声波层析成像反演方面也有所研究。论文的具体内容如下： 首先，本文对于Biot双相孔隙介质弹性波方程数值模拟计算中遇到的刚性问题开展了较深入的研究，提出了基于时间分解法的高阶交错网格有限算法，用于解决刚性问题，克服了刚性问题导致的数值计算（特别是低频情况）中的不稳定问题。具体的数值实例验证了该方法的有效性。通过数值算例分析了声波在双相孔隙介质的传播特征。 其次，在两种流体饱和的孔隙介质的研究方面，本文推导了Santos三相孔隙介质理论退化为经典Biot孔隙理论过程。在Zener粘弹性模型基础上，对Santos模型衰减机制进行了扩展研究。在考虑参考压力、高频校正及两种流体的粘滞耦合效应下，细致分析了含气饱和度和频率对Santos理论预期的四类体波速度和衰减的影响。并首次利用基于时间分解法的交错网格有限差分算法进行了相关声场的数值模拟，讨论了四种体波的传播特征。通过数值模拟实验，考察了储层参数孔隙度、渗透率、孔隙流体粘度和含气饱和度对纵波传播特性的影响。另外，将Santos模型与几种流行的孔隙介质扩展模型作了比较，也将Santos理论预计结果与实验数据作了对比分析。 第三，针对数值模拟中吸收边界条件这一重要的环节，本文分析和讨论了完全匹配层吸收边界条件在完全单相介质、Biot双相孔隙弹性介质及Santos三相孔隙介质中的应用情况。提出了定量考察吸收边界条件吸收外行波效果的数值分析方法。比较了完全匹配层与其他两种吸收边界条件，验证了完全匹配层方法的高效率。此外，基于频散关系守恒思想，本文提出了一种优化交错变网格有限差分算法，该算法在存在空间多尺度问题的井间声波数值模拟中可以极大地提高计算效率。文中详细讨论了该算法的计算效率和精度。 最后，本文对井间走时层析成像开展了一些基础工作。基于Gassmann-Wood孔隙介质模型，初步验证了走时层析成像动态监测气驱前缘的可行性。此外，本文还进行了井间声波实验测量，考察了管波的传播特点和路径。
英文摘要	During petroleum exploitation, more than 50% reservoir hydrocarbons are still left in formations, and are waiting for development. Finding remaining oil and gas in the reservoirs, and enhancing oil recovery, are both highly recognized jobs in petroleum industries. Meanwhile, they are related to many areas of research. In order to detect remaining oil and gas in the reservoirs, one must clearly understand the dynamic distributions of oil, gas and water. Also, they are crucial for monitoring CO2 sequestrations for reducing greenhouse gases in the air. Therefore, it is particularly desirable to establish more realistic models for hydrocarbon reservoirs, to thoroughly understand wave propagation in the multiphase fluid filled porous media, and to seek novel acoustic methods for delineating oil, gas and water distributions in the reservoirs. In this dissertation, acoustic propagation problems, associated with porous media filled with two immiscible fluids, are profoundly studied with theoretical analysis and numerical simulations. Cross-well acoustic tomography is also covered in the dissertation. The major contributions of the work can be shown in the followings: Firstly, a stiffness problem in the Biot’s poroelastic equations encountered for numerical simulations is treated. A time splitting method is developed to solve the stiffness problem with a staggered high-order finite-difference algorithm. By using this method, the instability phenomenon in numerical calculations, especially for the low frequency case, is solved. Numerical modeling examples demonstrate that, the results given by the proposed procedure are in good agreement with analytical solutions. In this part, the behaviors of acoustic wave propagation in two-phase porous media are also investigated through numerical examples. Secondly, as far as a porous medium is concerned saturated by two immiscible fluids, Santos’s three-phase equations are simplified into classical Biot’s ones, and the corresponding derivations are made. Employing the Zener viscoelastic model, attenuation mechanism of the Santos’s theory is generalized. By taking into account reference pressures, high frequency correction factors, and viscous coupling drag between the two fluids in the pores, the influences of frequency, and of non-wetting phase saturation, on phase velocities and inverse quality factors, for four body waves predicted by the Santos’s theory, are carefully discussed. Acoustic wave propagation in such three-phase media is simulated using the staggered finite-difference algorithm with the time splitting method developed in the work. The propagation behaviors of the four body waves are also analyzed. With numerical experiments, the influences of porosity, permeability, fluid property and gas saturation, on the velocities and amplitudes of three compressional waves, are explored. The Santos’s generalized model is compared with several porous media models, and velocities and inverse quality factors of the fast compressional and shear waves for the Santos’s theory are also compared with the experimental results. Thirdly, a perfectly matched layer (PML) method as an absorbing boundary condition in elastic single-phase media, in Biot’s two-phase porous media, and in Santos’s three-phase porous media, is discussed in detail. A numerical method to quantitatively evaluate the efficiency of an absorbing boundary condition to attenuate outgoing waves is established. The PML is compared with two kinds of absorbing boundary methods to confirm the efficiency of the PML. On the other hand, based on the dispersion-relation-preserving scheme, an optimized staggered variable-grid finite-difference algorithm is given in velocity-stress elastic wave equations. The proposed method is able to greatly improve computational efficiency for cross-well acoustic forward modeling for which a large variation of spatial scales exist in the horizontal direction, and the accuracy and efficiency of the developed scheme are verified. Finally, a preliminary study on cross-well traveltime tomography is discussed. From the Gassmann-Wood model, the feasibility for dynamically monitoring CO2 (gas) migration is validated. Also, a cross-well ultrasonic experiment is performed in order to understand the character of tube waves.
语种	中文
公开日期	2011-05-07
页码	126
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/160]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	赵海波. 不相混气液饱和孔隙介质声场数值模拟与应用研究[D]. 声学研究所. 中国科学院声学研究所. 2007.

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