Abstract: A method for magnetic ranging includes rotating a drilling tool in a drilling well in sensory range of an AC ranging signal emanating from a target well. The drilling tool includes a magnetic field sensor rotatably coupled thereto. The magnetic field sensor obtains a plurality of magnetic field measurements while rotating. The magnetic field measurements are mathematically back-rotated to obtain back-rotated magnetic field measurements which are in turn processed to obtain a measurement of the AC magnetic ranging signal emanating from the target well. The AC magnetic ranging signal is then processed to compute at least one of a distance and a direction from the drilling well to the target well.

Abstract: Acoustic communication apparatus for use with downhole tools are described. An example acoustic communication apparatus for use in a wellbore includes a first acoustic transducer to generate first acoustic signals. The first acoustic transducer is mounted in an interior of a first drill collar to transmit the first acoustic signals via at least a portion of a body of a drillstring or a mud channel within the drillstring to a second drill collar. Additionally, the example acoustic communication apparatus includes a first receiver mounted to the first drill collar to receive second acoustic signals transmitted from the second drill collar.

Abstract: Acoustic communication apparatus for use with downhole tools are described. An example acoustic communication apparatus for use in a wellbore includes a first acoustic transducer to generate first acoustic signals. The first acoustic transducer is mounted in an interior of a first drill collar to transmit the first acoustic signals via at least a portion of a body of a drillstring or a mud channel within the drillstring to a second drill collar. Additionally, the example acoustic communication apparatus includes a first receiver mounted to the first drill collar to receive second acoustic signals transmitted from the second drill collar.

Abstract: The disclosure relates to methods and apparatus for determining the velocity of an ultrasound pulse in drilling fluids in downhole environments. A method for determining a velocity of ultrasound propagation in a drilling fluid in a downhole environment includes emitting an ultrasound pulse into the drilling fluid in a borehole using a first ultrasound transducer (37); detecting the ultrasound pulse after the ultrasound pulse has traveled a distance (d); determining a travel time (t) required for the ultrasound pulse to travel the distance (d); and determining the velocity of ultrasound propagation from the known distance (d) and the travel time (t).

Abstract: An enclosure for housing a transducer and electronics for disposal on a downhole tool. A transducer is disposed at an angle with respect to a longitudinal axis of the enclosure, wherein the enclosure contains a fluid surrounding the transducer. Enclosures also include transducers linked to motor means for selective rotation of the transducers within the enclosure. Enclosures with transducer arrays for phased or targeted signal transmission/detection.

Abstract: A borehole caliper tool includes a tool body, a bow spring flexibly coupled to the tool body, a target coupled to the bow spring, and an ultrasonic transducer coupled to the tool body, wherein in operation the ultrasonic transducer transmits an acoustic pulse to the target and receives an echo of the acoustic pulse from the target.