【摘要】 为适应大斜度井/水平井钻井需求,提高复杂地层随钻电磁波测井响应数值模拟的计算速度和精度,引入了三维柱坐标系亚网格技术及共形网格技术。亚网格技术针对线圈、井眼等精细结构处采用局部自适应细网格剖分,模拟均匀无限厚地层随钻电磁波测井响应;与传统时域有限差分(FDTD)计算结果进行了精确性对比验证;采用三维柱坐标系共形网格算法,模拟随钻电磁波仪器偏心时的测井响应,与阶梯近似、一维半数值解进行对比。均匀无限厚地层亚网格技术模拟结果相对误差控制在0.8%以内,计算时间约为传统FDTD的19%;仪器偏心时,在计算时间保持稳定的前提下,共形网格技术将模拟精度提高至阶梯近似的3.42倍。以上2种算法可为复杂地层的环境校正和随钻快速反演提供支持。更多还原

【Abstract】 In order to adapt to the requirements of high angle and horizontal wells drilling,improve calculation speed and precision of numerical simulation of electromagnetic LWD response in the complex formation conditions,this paper introduces subgridding method and conformal mesh method for three-dimensional cylindrical coordinate system.Firstly,the coil,borehole and other fine structure are concerned by adaptive subgridding method,simulated electromagnetic LWD response in homogeneous infinite thick,and compared accuracy with traditional FDTD computing results.Then,conformal mesh algorithm for three-dimensional cylindrical coordinate system is used,to simulate electromagnetic LWD response with tool eccentricity,and compare the simulation results with ladder approximation and the semi-analytic results.Results show that under the geological conditions of infinite uniform thickness,the subgridding technology simulation results relative error is controled within 0.8%,and computing time is about 19% of the traditional FDTD.The simulation precision of conformal grid technology is 3.42 times of staircase approximation with tool eccentricity,and computing time remained stable.Therefore,the two algorithms can provide strong support for environment correction of complex formation and rapid inversion with drilling.更多还原