Reply to the comment by D. F. Rucker 'T. Zhu and R. Feng, Resistivity tomography with a vertical line current source and its applications to the evaluation of residual oil saturation'

I thank Dr. D. F. Rucker for his comment (Rucker, 2012) on our paper (Zhu and Feng, 2011) about how to get Eq. (4) calculating normal potential at point P (xp, yp, zp) in an electric field generated by vertical line current source A. The essential criticism he gives concerning our work is that we started from an incorrect equation in the development of Eq. (4). After I checked it carefully again and again, I have to accept the fact that the starting equation used in our paper is incorrect. Now I made some revisions listed as follows. Eq. (1) in our paper should be replaced by