中文摘要：

为模拟仪器偏心条件下随钻电磁波测井响应,为随钻仪器偏心校正提供理论基础,基于时域有限差分（FDTD）进行随钻电磁波仪器偏心条件下响应模拟与分析。采用柱坐标系非均匀网格与＂阶梯近似＂实现对井眼、线圈和仪器偏心的精细模拟,采用各向异性完全匹配层（UPML）实现对反射场的吸收,以减小模型计算规模,从而提高计算速度。通过与一维解析解和偏心条件下半解析解对比,验证了算法的正确性。采用哈里伯顿EWR-Phase4随钻电磁波测井仪,对不同钻井液电阻率、井眼尺寸、发射频率与不同线圈距条件下的仪器响应进行模拟。结果表明：相位差电阻率较幅度比电阻率更易受仪器偏心的影响;线圈距越大、井眼越大、发射频率越高,测井响应受仪器偏心影响越大;对常规砂泥岩地层,当发射频率为2 MHz,钻井液电阻率小于0.1Ω·m时,需要对中源距与深源距响应进行偏心校正。

英文摘要：

In order to model the electromagnetic logging responses while drilling with tool eccentricity and to provide theoretic basis for the eccentricity correction, the responses with tool eccentricity were simulated and analyzed based on the finite- difference time-domain （FDTD） framework. Non-uniform gridding technique in cylindrical coordinates and staircase approximation technique were utilized to reach fine simulation of borehole, coils, tool eccentricity. In addition, the UPML absorbing boundary condition was implemented to absorb reflection field, which could reduce the model size and improve simulation speed. By comparing the simulation results with the one-dimension analytical solution and the semi-analytic results with tool eccentricity, the algorithm was verified favorably. In addition, the responses of the Halliburton EWR-Phase4 Electromagnetic LWD tool under different eccentricity distances, mud resistivity, borehole sizes, coil-spacing and frequencies were simulated. The results show that the phase difference resistivity is affected more by tool eccentricity than the attenuation resistivity. With larger coil-spacing and borehole size and higher frequency, the responses are more sensitive to tool eccentricity. In conventional sand-shale reservoirs, for 2 MHz frequency, eccentricity correction needs to be applied to the responses of middle coil-spacing and long coil-spacing when the mud resistivity is less than 0.1 12 Ω·m.