Patent ID: 6703833
Filing Date: 2004-03-09
Classification: G01N,G01V

Abstract:
An apparatus for determining a parameter of interest of a subsurface formation in the vicinity of s borehole comprising:(a) a magnet arrangement on a downhole tool for producing a static magnetic field in a region of examination in the formation and aligning nuclear spins in said region substantially parallel to a direction of said static magnetic field in said region; (b) a transmitter coil on the downhole tool for transmitting a pulsed radio frequency (RF) magnetic field into said region of examination, said transmitter coil having windings around a toroidal (tubular) core, said toroidal core intensifying the magnetic flux in the first coil, said pulsed RF field substantially perpendicular to said static field and inducing precession of nuclear spins in said region of examination; (c) a first receiver coil receiving a first component of echo signals from said precessing nuclear spins and producing a first signal; (d) at least one additional receiver coil on the downhole tool for receiving a second component of echo signals from the precessing nuclear spins and producing at least one second signal, said second component substantially orthogonal to the first component, and (e) a processor for combining the first signal and the at least one second signal to determine the parameter of interest.