采用混合法和递推矩阵算法模拟层状介质中随钻电磁波电阻率测量仪器的响应

Simulating electromagnetic wave resistivity MWD tool 's response in stratified media using hybrid method and recursive matrix algorithm

关键词:  电测井  混合法  递推矩阵算法  电磁波电阻率  随钻测量  层状介质

Key words:  electric logging  hybrid method  recursive matrix algorithm  electromagnetic wave resistivity  measurement-while-drilling (MWD)  stratified media

摘要:

将混合法与递推矩阵算法相结合计算轴对称条件下二维层状介质中随钻电磁波电阻率测量仪器的响应。根据层界面处电磁场的连续性条件得到确定所有待定系数的矩阵方程组并通过递推方法快速求解,以摒弃繁琐的上行波和下行波模式并避免指数增加项的出现。利用上述算法分析井眼、侵入和钻铤凹槽对随钻电磁波电阻率测井响应的影响。结果表明,由于金属钻铤的存在导致井眼内钻井液所占空间相对变小,从而使钻井液对接收线圈响应的影响变小;钻铤凹槽对随钻电磁波电阻率测量仪器相位差和幅度比的影响可忽略不计,但对单个接收线圈处电磁信号的相位和幅度产生明显影响,并且对幅度的影响大于对相位的影响。

Abstract:

The hybrid method and the recursive matrix algorithm were combined to compute the electromagnetic wave resistivity MWD tool 's response in cylindrically symmetrical 2-D stratified media. A matrix equation group for ascertaining all the coefficients was obtained according to the continuity condition of electromagnetic fields at the interfaces, which can be solved rapidly via a recursive algorithm. Thus the tedious mode of up-going and down-going waves was abandoned and the appearance of exponentially increasing terms has been prevented. The influence of borehole, invasion and collar groove on electromagnetic wave resistivity MWD tool 's response was analyzed by the combined hybrid and recursive matrix method. The results show that the influence of drilling fluid on the receiver coil 's response is weakened since the space occupied by the drilling fluid within the borehole is reduced by the existence of metal drilling collar. The influence of the collar groove on the MWD tool 's phase difference and amplitude ratio can be neglected, but the collar groove has exerted distinct influence on the single receiver coil 's phase and amplitude. The collar groove 's influence on amplitude is more obvious than that on phase.