Abstract: A method and apparatus for determining a characteristic of an earth formation surrounding a borehole in which a pulsed nuclear magnetic resonance (NMR) tool is received. A static magnetic field is produced in the borehole using at least two spaced-apart magnets in the NMR tool. The static magnetic field has a first region of substantially uniform magnetic intensity at a first location in the borehole, the first location in the borehole having a first temperature. The NMR tool is moved to a second location in the borehole having a second temperature, and a static magnetic field having a second region of substantially uniform magnetic is produced. The at least two spaced-apart magnets are controllably moved relative to each other wherein the first region of substantially uniform magnetic intensity and the second region of substantially uniform magnetic intensity are substantially equal in size and distance from the NMR tool.

Abstract: A method and apparatus for determining a characteristic of an earth formation surrounding a borehole in which a pulsed nuclear magnetic resonance (NMR) tool is received. A static magnetic field is produced in the borehole using at least two spaced-apart magnets in the NMR tool. The static magnetic field has a first region of substantially uniform magnetic intensity at a first location in the borehole, the first location in the borehole having a first temperature. The NMR tool is moved to a second location in the borehole having a second temperature, and a static magnetic field having a second region of substantially uniform magnetic is produced. The at least two spaced-apart magnets are controllably moved relative to each other wherein the first region of substantially uniform magnetic intensity and the second region of substantially uniform magnetic intensity are substantially equal in size and distance from the NMR tool.

Abstract: The invention is a control device or directional drilling tool. The control device has an electromotor drive in the orienting device. The measuring and control device is situated between the orienting device and the drill string. Cable lead-throughs through the orienting device are eliminated. The electromotor drive of the orienting device can be actuated independently of drilling operations, making it possible to perform a rapid and precise performance of an orientation process while continuing drilling operations, reducing deviations from the planned drilling program.