倾斜井眼中感应测井正演模拟与响应特征

Forward Modeling of Induction Well Logging Tools in Dipping Boreholes and Their Response

感应测井仪器的发射源可简化为一系列磁偶极子,其在层状地层中产生的电磁场可分解成彼此独立的TE波和TM波叠加,且TE波和TM波完全由两个标量方程确定.首先研究倾斜井眼中磁偶极子场的TE波和TM波分解,推导多层介质中电磁场振幅以及地层界面上广义反射和透射系数的递推公式,给出层状地层电磁场解析解.然后利用数值结果分析考察砂泥岩薄交互层中,地层层厚、井眼倾角变化等对感应测井响应的影响.

The transmitters of induction well logging tools can be simplified as a series of magnetic dipoles, whose fields formed in dipping boreholes can be decomposed as the sum of transversal electrical and transversal magnetic waves (TE and TM waves), and solved completely from the two scalar partial differential equations. A new process is first given to decompose the electromagnetic field into TE and TM waves through the tensor expression of Maxwell equations in the cylinder system, and then recurrence formula for amplitudes of the field in each bed and generalized reflection and transmission coefficients on each boundary are given. On the bases, the analytic solution of the field in each bed is obtained. Finally, using numerical results, the influence of dipping angles of boreholes, bed thickness and thinly laminated sand/shale on the response of the deep induction well logging tools is investigated.