Abstract: Electromagnetic free point tools are configured to determine the free point of a downhole pipe in a wellbore utilizing the amplitude or phase change in a transmitted signal for stressed and unstressed pipe. Certain examples of electromagnetic free point tools comprise a housing, one or more transmitter coils, one or more receiver coils, each coil spaced apart from one another, a power source for applying an oscillating voltage to the one or more transmitter coils which then induces a current in the receiver coil(s), and electronics for measuring the induced current in the receiver coil(s). In another embodiment, at least one of the coils is axially adjustable in position within the tool to permit the relative distance between coils to be adjusted to optimize performance of the tool in various conditions. By measuring the amplitude or phase of the induced current relative to the oscillating voltage, a log of the amplitude or phase is generated while passing the tool through a length of unstressed pipe.

Abstract: Electromagnetic free point tools are configured to determine the free point of a downhole pipe in a wellbore utilizing the amplitude or phase change in a transmitted signal for stressed and unstressed pipe. Certain examples of electromagnetic free point tools comprise a housing, one or more transmitter coils, one or more receiver coils, each coil spaced apart from one another, a power source for applying an oscillating voltage to the one or more transmitter coils which then induces a current in the receiver coil(s), and electronics for measuring the induced current in the receiver coil(s). In another embodiment, at least one of the coils is axially adjustable in position within the tool to permit the relative distance between coils to be adjusted to optimize performance of the tool in various conditions. By measuring the amplitude or phase of the induced current relative to the oscillating voltage, a log of the amplitude or phase is generated while passing the tool through a length of unstressed pipe.

Abstract: A gravel pack evaluation tool comprised of a low energy radiation source and multiple directionally-collimated radiation detectors to analyze small, azimuthal segments of a gravel pack. Methods of use are also provided. Collimators and radiation shielding used in conjunction with multiple detector arrays allow an azimuthal segmented view of a gravel pack, particularly at certain defined depths into a gravel pack. Radioactive tracers may be used in conjunction with these tools to produce enhanced images of gravel packs and formations.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: An NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: An NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: An NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: A system includes a wellbore tool disposed in a wellbore and a surface apparatus disposed at a surface of the wellbore. Prior to operating the tool to take an initial measurement, the wellbore tool is first calibrated to take into account magnetic junk which is magnetically attracted to and accumulated on a magnet housing of the tool. To calibrate the tool, a new tuning frequency, called the Larmor frequency, is determined, and the tool is tuned to the new Larmor frequency before taking an initial measurement. The wellbore tool and the surface apparatus each include a processing system. Each processing system includes a memory. A first part of a tuning frequency determination software is stored in the memory of the tool, and a second part of the frequency determination software is stored in the memory of the surface apparatus. To determine the tuning frequency, the processing system in the wellbore tool initiates execution of the first part of the tuning frequency determination software.

Abstract: NMR logging apparatus is provided which produces a strong, static and homogeneous magnetic field B.sub.0 in a Volume of an adjacent formation on one side of the tool to measure nuclear magnetic resonance characteristics thereof at two different depths of investigations. In the preferred embodiment, the tool has an RF antenna mounted on the outside of the metal body of the tool, directing focused oscillating magnetic fields B.sub.1 at said Volume to polarize or tip the magnetic moments of hydrogen nuclei of fluids within rock pores. The same antenna can be used to receive signals of proton precession in the Volume of interest immediately after transmission of the RF polarizing field B.sub.1. One of the NMR readings is employed to compensate for inaccuracies in the other NMR reading to provide an overall improved NMR log.