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相比泥浆脉冲传输而言,随钻电磁波传输方式具有不依赖钻井泥浆介质循环、信息传输快等优点,此外,电磁波对于地层电阻率反映灵敏度高,便于及时发现矿产目的层.正是基于上述特点,近年来随钻电磁波传输系统越来越广泛地应用于石油、天然气和煤层气(煤矿)等矿产资源的开发.文中采用不同于以往的随钻电磁波传输分析方法,即根据电磁波在地层中传播规律和极低频(extremely low frequency, ELF)电磁波的近场辐射特性,采用等效电路法对随钻电磁波在地层信道中的传输进行分析.此外,根据等效电路分析结果,利用地面接收电磁波信号幅度包络瞬时变化率大小来作为判断地层电阻率特性的条件.山西沁水煤层探测案例实际结果验证了提出的方法在煤炭等矿产资源探测方面具有明显时效性,进一步证明了随钻电磁波信息传输系统可以同时兼作一种有效的实时测井系统. 相似文献
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磁矢位的边值问题是"电磁场"课程中关于恒定磁场的教学重点,也是学生普遍反映的难点。本文对平行平面场中磁矢位的边界方程,进行了证明,同时给出了该方法的应用;对比分析了利用磁矢位边界方程与安培环路定理两种方法的求解。本文解决了"电磁场"课程教学中的一个盲点,让学生建立起了平行平面场中磁矢位的边界方程与磁场强度和磁通密度边界条件的联系,对理解恒定磁场的本质大有裨益。 相似文献
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本文首先将矢量空间的概念推广到并矢,建立了求解并矢格林函数的算子法,然后用分布论严格地导出了磁型并矢波动方程的一种新的表达式。文末以广义柱形波导为例,具体阐述本文方法的运用。 相似文献
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本文对一维光子晶体的双折射特性进行了数值和理论的计算.分析了低频及带边电磁波的双折射特性.在低频近似下导出了一维光子晶体对横电波(TE波)和横磁波(TM波)的折射率方程.当构成周期结构的两种介质的厚度相同时,折射率椭球的偏心率最大,光子晶体对两种不同偏振态的电磁波的双折射效应最明显. 相似文献
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随钻测量技术广泛应用于钻井、测井、地质分析等工程中,无磁随钻测量定向接头是井下随钻测量仪器的重要部件,通过研究无磁随钻测量定向接头的失效形式并加以分析,使我们从中得到了无磁随钻测量定向接头的腐蚀失效原因,并知道腐蚀失效的存在会增加接头断裂的风险率.为此我们会在日常维护中利用外观检测和超声波检测仪对设备加以检测,以排除隐患来降低事故的发生率. 相似文献
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介质加载圆柱腔的并矢格林函数 总被引:2,自引:0,他引:2
本文首先利用Ohm-Rayleigh法求出了介质加载圆柱腔的标量格林函数;然后,利用并矢格林函数构造法导出了介质加载圆柱腔的磁型并矢格林函数;最后,利用Gm法导出了其电型并矢格林函数. 相似文献
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本文给出了混合颗粒媒质的定义,并推导出媒质中平均电磁波与散射电磁波所满足的方程。在稀疏媒质情况下,对方程进行了化简。作为所建立理论的一个实际运用,我们推导出求解复合材料等效介电常数的公式,其计算值与实验值符合很好。 相似文献
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条带型接收换能器是随钻声波测井仪的关键器件,其声学性能直接影响测量信号的质量。利用有限元法对条带型接收换能器进行设计分析。结果表明,接收换能器中的压电片采用并联接线方式接收灵敏度较高,在钻铤波隔声阻带内接收灵敏度起伏小于20 dB。在此基础上分析了压电片个数及几何尺寸对换能器接收灵敏度的影响。条带型接收换能器的压电片个数越多,压电片厚度越大,钻铤波隔声阻带范围内接收灵敏度越高,有利于提高地层波信号测量;压电片高度越大,压电片宽度越小,钻铤波通带范围内灵敏度越低,有利于降低钻铤波信号能量。数值模拟结果对随钻声波测井仪条带型接收换能器的设计及制作有良好的指导作用。 相似文献
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Dagang Wu Ji Chen Liu C.R. 《Geoscience and Remote Sensing, IEEE Transactions on》2008,46(6):1652-1656
In this paper, an unconditionally stable finite- difference time-domain (FDTD) method in cylindrical coordinates is developed to analyze electromagnetic responses under axially symmetric measure-while-drilling/logging-while-drilling (MWD/LWD) environments. The method is based on the application of the Crank-Nicholson scheme to the FDTD method in cylindrical coordinates. To accelerate the solution of this approach, an algebraic multigrid method is applied. For several MWD/LWD electromagnetic simulations, it is observed that the proposed method can be close to 20 times faster than the conventional FDTD method. 相似文献
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Cylindrical FDTD Analysis of LWD Tools Through Anisotropic Dipping-Layered Earth Media 总被引:2,自引:0,他引:2
Electrical logging-while-drilling (LWD) tools are commonly used in oil and gas exploration to estimate the conductivity (resistivity) of adjacent Earth media. In general, Earth media exhibit anisotropic conductivities. This implies that when LWD tools are used for deviated and horizontal drilling, the resulting borehole problem may include dipping-layered media with dipping beds having full 3 times 3 conductivity tensors. To model this problem, we describe a 3-D cylindrical finite-difference time-domain (FDTD) algorithm extended to fully anisotropic conductive media and implemented with cylindrical perfectly matched layers to mimic open-domain problems. The 3-D FDTD algorithm is validated against analytical results in simple formations, showing good agreement, and used to simulate the response of LWD tools through anisotropic dipping beds for various values of anisotropic conductivities and dipping angles 相似文献
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设计了一种基于金属基片结构的随钻四极子复合发射换能器。采用有限元法数值模拟了换能器的频域及时域声学响应,考察了钻铤结构及声源激励脉冲宽度对其声学特性的影响,实际封装制作了发射换能器并进行了消声水池实验测试。测试结果表明,该发射换能器的谐振频率、发射电压级及水平指向性与数值模拟结果吻合较好。该换能器在频率4.7 kHz附近存在一阶弯曲振动模态,其发射电压级可达126.2 dB,具备低频、大功率的辐射特点,可满足随钻四极子声波测井需求。 相似文献
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R. S. Chen Edward K. N. Yung 《Journal of Infrared, Millimeter and Terahertz Waves》2002,23(5):799-810
An efficient numerical method has been devised for the study of wave circulated by a magnetised ferrite sphere. It is a finite-difference time-domain formulation that incorporates Mur's absorbing boundary conditions and a perfectly matched layer. The electromagnetic fields inside the ferrite body are calculated using special updating equations derived from the equation of motion of the magnetization vector and Maxwell's curl equations in consistency. The electromagnetic fields inside ferrite and the power-density distribution on the ferrite's surface normal to the bias external magnetic field are obtained in a wide frequency band with a single time domain run. It is observed that an incident plane wave would circulate around the magnetised ferrite body in an open space as if the ferrite were placed inside a waveguide / microstrip junction circulators. 相似文献
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电磁场同物质相互作用问题可以归结为电磁场同不同折射率形成的"势场"相互作用问题。当电磁场(光子)在周期"势场"中传播时,能量将分裂成带。文章从麦克斯韦方程出发,讨论了电磁场与周期介质的相互作用,并用转移矩阵方法导出了系统的色散关系,描述了周期介质中布洛赫波的传播及系统的稳定性。 相似文献
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A. G. Kyurkchan E. A. Skorodumova 《Journal of Communications Technology and Electronics》2009,54(6):625-636
An efficient method is proposed for solving the problem of electromagnetic wave diffraction by dielectric bodies of complex shapes. Scattering patterns are decomposed in vector spherical harmonics to reduce the problem to a system of algebraic equations. It is shown that the method exhibits a high convergence rate that depends on the complexity of a scatterer’s boundaries only slightly. Examples of simulation of the characteristics of wave scattering by various complex bodies are considered. The correctness of the obtained data is verified through checking the fulfillment of the optical theorem. 相似文献