Stray currents of ESP well casings

Comprehensive field measurements and simulation using three-dimensional (3D) boundary element analysis system (BEASY) software package of electrical submersible pump (ESP) well casings have been conducted to (a) investigate the effectiveness and applicability of pulse cathodic protection (PCP) system, (b) find out the sources of stray currents, (c) suggest a practical solution to reduce the galvanic cell current between the steel well casings and the four copper earthing rods used in the ESP earthing system, and (d) check the possibility of utilizing unused well casings as anodebed energized by the conventional cathodic protection (CP) to protect many nearby well casings. Field measurements and theoretical simulation reveal that the PCP current is DC with superimposed ripples having the same frequency of the voltage pulses (∼3 kHz). Hence there is a doubt about the effectiveness of the PCP systems for protecting deep well casings. The naturally created galvanic cells generate a pure DC current up to 1000 mA, and it can be reversed by using aluminum earthing rods instead of copper ones. Simulation has proven the superiority of utilizing unused well casings as anodes and it represents a promising means for having quasi-uniform current-density profiles along the axial length of the protected well casings.