Induction borehole logging method and apparatus having means for balancing out a quadrature phase component and means to render the balancing means inoperative when a predetermined condition occurs

Claim 1

IN AN INDUCTION WELL LOGGING SYSTEM WHEREIN A TRANSMITTER COIL IN A BORE HOLE LOGGING TOOL INDUCES A QUADRATURE COMPONENT IN A RECEIVER COIL WHILE SIMULTANEOUSLY INDUCING EDDY CURRENTS IN AMBIENT FORMATIONS, WHICH EDDY CURRENTS, IN TURN, CAUSE AN IN PHASE COMPONENT TO BE INDUCED IN SAID RECEIVER COIL, THE METHOD COMPRISING THE STEPS OF RECORDING SUBSTANTIALLY ONLY THE IN PHASE COMPONENT WHEN AND AS SAID LOGGING TOOL TRAVERSES FORMATIONS OF LOW CONDUCTIVITY AND RECORDING THE VECTORIAL SUM OF SAID COMPONENTS INDUCED IN THE RECEIVER COIL WHEN SAID LOGGING TOOL TRAVERSES FORMATIONS OF CONDUCTIVITY GREATER THAN SAID LOW CONDUCTIVITY, SAID VECTORIAL SUM BEING A SUMMATION OF SAID COMPONENTS WHEN SAID QUADRATURE COMPONENT IS PRESENT IN EFFECTING SUCH SUMMATION.