Apparatus and method for measuring velocity and composition of material in and adjacent to a borehole

A method of measuring flow in or around a region of interest in a borehole in an earth formation, comprising:

• inserting a flow measurement device into the borehole in the earth formation, the flow measurement device comprising a magnet, an electromagnet disposed around the magnet, and a radio frequency (RF) coil disposed around the magnet;
• generating, using the magnet, a static solenoidal magnetic field, wherein the static solenoidal magnetic field has a field intensity that decreases in strength peripherally from the magnet;
• generating, using the electromagnet, a time varying solenoidal magnetic field;
• generating, using the RF coil, an RF magnetic field transverse to the static solenoidal magnetic field and rotating at a Larmor radio frequency corresponding to the field intensity in the region of interest around the flow measurement device;
• and
• receiving a received signal induced in the RF coil by a magnetic field around the RF coil.