Induction logging utilizing resistive and reactive induced signal components to determine conductivity and coefficient of anisotropy

Apparatus for determining the coefficient of anisotropy of formations surrounding a borehole, comprising:

• a transmitter coil having an axis substantially perpendicular to the borehole axis;
• a receiver coil spaced from said transmitter coil and having an axis which is substantially parallel to the axis of said transmitter coil;
• means for energizing said transmitter coil;
• means for detecting the resistive and reactive components of the signals induced in said receiver coil;
• and
• means responsive to the detected components for obtaining a measure of the coefficient of anisotropy of said formations.

Apparatus for determining the vertical and horizontal conductivities of formations surrounding a borehole, comprising:

• a transmitter coil having an axis substantially perpendicular to the borehole axis;
• a receiver coil spaced from said transmitter coil and having an axis which is also perpendicular to the borehole axis;
• means for energizing said transmitter coil;
• means for detecting the resistive and reactive components of signals induced in said receiver coil;
• and
• means for combining said detected resistive and reactive components to determine the vertical and horizontal conductivities of said formations.

A method for determining the vertical conductivity of formations surrounding a borehole, comprising the steps of:

• suspending spaced transmitter and receiver coils in the borehole, the coils having axes which are substantially parallel to each other and substantially perpendicular to the borehole axis;
• energizing the transmitter coil;
• detecting the resistive and reactive components of the signals induced in the receiver coil;
• and
• determining formation vertical conductivity from said detected resistive and reactive components.

A method for determining the vertical and horizontal conductivities of formations surrounding a borehole, comprising the steps of:

• suspending spaced transmitter and receiver coils in a borehole, the transmitter and receiver coils having substantially parallel axes which are substantially perpendicular to the borehole axis;
• energizing the transmitter coil;
• detecting the resistive and reactive components of signals induced in the receiver coil;
• and
• combining the detected resistive and reactive components to determine the vertical and horizontal conductivities of said formations.