非均质地层中直流电测井的正反演

FORWARD AND INVERSION OF DIRECT CURRENT WELL LOGGING ABOUT INHOMOGENEOUS FORMATION

针对井周的非均质地层模型，利用三维有限元方法模拟了方位梯度电极系的测井响应。在非均质程度比较小的情况下，各个方位上的响应之间差别不大，与真实的电阻率分布差别也不大；反之，则差别很大。所测得的响应远远低于较高的真电阻率值，而是靠近较低的真电阻率值，因此，有必要对测井响应进行校正。利用非线性反演方法求取真实的电阻率分布，克服了传统的校正方法的弊端。数值模拟的结果表明，此方法是可行的。

By using the 3D finite element method, the response of the azimuthal lateral sonde about the inhomogeneous formation model around a well was simulated. In the less inhomogeneous situation, the response on each azimuthal has less difference with the true resistivity distribution and others. Otherwise, the difference is great. The value of response is much lower than the high resistivity values and much coser to the low resistivity value. So the correction is necessary.The true resistivity distribution was solved with the nonlinear inversion method due to the drawbacks of the old correction methods. The numerical simulation shows that this method is feasible.