Propagation anisotropic well logging system and method

摘要

An anisotropic well logging system includes a well logging tool including a first transmitter coil spatially arranged within the well logging tool in a first predetermined manner and a second transmitter coil spatially arranged within the well logging tool in a second predetermined manner which ultimately transmits electromagnetic energy into the formation at a frequency which enables electromagnetic energy to propagate through the surrounding earth formation. A first pair of receiver coils spaced a predetermined distance from each other and from the first transmitter coil and spatially arranged within the well logging tool in the same manner as the first transmitter coil provides signals in accordance with the received electromagnetic energy. A second pair of receiver coils spatially arranged within the logging tool in the same predetermined manner as the second transmitter coil and spaced a predetermined distance from each other and another predetermined distance from the second transmitter coil provides signals in accordance with the received electromagnetic energy. A control apparatus controls the first and second transmitters so they alternately transmit the electromagnetic energy into the earth formation and also provides a control signal. Processing apparatus responsive to the control signal from the control apparatus provides one output representative of the vertical resistance of the earth formation and a second output representative of the horizontal resistance of the earth formation in accordance with the signals from the four receivers.