On Numerical Calculation Precision in Cased Hole Electric Field

It is important to calculate electric potential value in borehole axis accurately for obtaining formation resistivity.With regard to this,the precesion and stability of cased hole electric field numerical computation in the process of cased hole formation resistivity logging data are studied.Introduced is the principle of cased hole formation resistivity logging.Two methods,integration and residue method,for calculating cased hole electric potential value in borehole axis are given.The electric potential value calculated by the integration method is acceptable when the electric field spacing is near.But its results are unstable for the oscillation of the integrated function.The electric potential value calculated by the residue method decreases fast exponentially when the electric field spacing increases.It shows the electric field physical laws and its precision is higher.Numerical calculation results show that the stability and precision of electric potential value computed by the residue method is higher than that computed by the integration method.