Systems and Methods for Downhole Electric Field Measurement

A downhole electromagnetic field measurement system that comprises:

• a first downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor that includes:
• a first surface that is at least partially reflective;
• a second surface that is at least partially reflective, said second surface suspended by one or more flexible members to define an optical cavity having a variable distance between the first and second surfaces;
• and
• a first conductive layer attached to the second surface and having a first electric charge, wherein an electric field passing through the optical cavity interacts with the first electric charge and displaces the second surface to alter the variable distance and cause a spectrum variation in light exiting the sensor;
• a transmitter that induces an electromagnetic field within a formation surrounding the first sensor, wherein variations in the electric field correspond to variations in the electromagnetic field;
• and
• a computer that processes optical signals received from the first sensor to measure said electromagnetic field and to derive a formation property based at least in part on said electromagnetic field.

A method for measuring an electromagnetic field using one or more downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor, the method including:

• inducing an electromagnetic field into a formation surrounding a borehole;
• exposing a first conductive layer to an electric field, the first conductive layer having an electrical charge and being attached to one of two surfaces that are at least partially reflective, and the two surfaces defining an optical cavity within a first sensor having a variable distance between the two surfaces;
• directing to the borehole surface light exiting the first sensor;
• detecting a spectrum variation in the light exiting the first sensor, the electric field interacting with the electrical charge and causing a displacement of the one of two surfaces to alter the variable distance and cause the spectrum variation;
• and
• processing a first signal representing the detected spectrum variation to measure said electromagnetic field and to derive a formation property based at least in part on said electromagnetic field.