Patent ID: 7501817

Claim:
An apparatus for generating a magnetic field, comprising: a) a drilling means for drilling a borehole into the formation; b) a means for carrying drilling fluid through the drilling means; c) a measuring means, connected to the drilling means, for making nuclear magnetic resonance measurements while the borehole is being drilled, the measuring means comprising: i) a means for producing a plurality of axisymmetric static magnetic fields through the drilling means and into the formation at a plurality of regions of investigation such that the contour lines generated by the static magnetic fields are substantially straight in the axial direction at a depth of investigation where the nuclear magnetic resonance measurements are obtained, comprising: a) an axially magnetized upper magnet; b) an axially magnetized central magnet; c) an axially magnetized lower magnet; ii) an antenna for producing an oscillating magnetic field in the formation; wherein the upper magnet and central magnet generate a static magnetic field having a high gradient at a first region of investigation.