Abstract: The invention relates to nondestructive inspection apparatus for automatically inspecting the end region of a tubular member and a coupling member secured to that end region. An inspection probe is yieldingly received within a housing that is pivotally supported on an arm that moves helically around the tubular member. The probe is extended outwardly from an air chamber in the housing to contact the surface of the tubular member. When the probe encounters the obstructing shoulder of the coupling on the end of the tubular member, the housing is caused to pivot to activate an air escape mechanism to reduce the air pressure in the chamber and cause the probe to be withdrawn radially to hop over the obstructing shoulder on the coupling. The housing then returns to its original position to terminate the air escape from the chamber. Air pressure builds up again to force the probe outwardly onto the surface of the coupling.

Abstract: A method and apparatus is disclosed for electrically measuring the inside diameter of a metallic pipe such as oil or gas well casing. The transimpedance of two coaxial coils within the pipe is determined and then resolved into its inphase and quadrature components. The difference of the magnitudes of the two components, .DELTA.Z, is approximated by a function independent of the electrical properties of the pipe but which is a function of the inside diameter of the pipe. The inside diameter is determined from the function in response to the measured .DELTA.Z and may be recorded as a function of travel distance in the pipe.

Abstract: A method and apparatus is disclosed for electrically measuring the inside diameter of a metallic pipe, such as oil or gas well casing. The transimpedance of two coaxial coils within the pipe is determined and then resolved into its inphase and quadrature components. The difference of the magnitudes of the two components is equal to an expansion equation which is a function of the inside diameter of the pipe and a factor proportional to the ratio of the permeability to the conductivity of the pipe. The inphase component of the impedance is equal to a second expansion equation which is a function of the inside diameter of the pipe and the factor proportional to the ratio of the permeability to the conductivity of the pipe. The two equations are solved simultaneously to generate signals for the pipe's inside diameter and the ratio of permeability to conductivity.

Abstract: Apparatus for indicating the location of casing joints or collars in a cased borehole utilizing a magnetic field. An electrical detector coil array is disposed within an elongated body member having a plurality of arm member equidistant thereabout. Each arm member carries a casing contact pad having a permanent magnet mounted therein. The expansion force exerted on the arm members and the maximum range of expansion are independently adjustable.

Abstract: A combination of magnetics and a special geometric environment is employed to distinguish whether an instrument is positioned within a pipe formed of magnetizable or non-magnetizable material, and is the basis, in part, for a method and an apparatus used in controlling picture taking at the bottom of a well bore. A coil is energized repetitively in a circuit in which the voltage across the coil, or the current that flows through the coil, can be measured. Whether the coil is in a magnetic or non-magnetic environment is determined by the magnitude of the change in coil voltage or current.

Abstract: As the outrigger arms of a borehole logging tool are flexed inwardly and outwardly according to the diameter of the borehole opening through which they pass, the corresponding axial displacements of the ends of the arms are controlled to determine the axial positions of the arms relative to the tool. Specifically, as the arm ends move, they are caused to rotate by a cam mechanism. The stiffness of the arms causes the arm ends to rotate in unison, and the exact positions of the arms on the tool are then controlled by the differential movements of the arm ends in the cams.

Abstract: An electrical signal representative of the detection of a mechanical coupling within a string of tubular goods is coupled into one input of each of a pair of parallel configured comparators. When the input signal level exceeds the value of complimentary reference levels the respective comparator generates an output signal. The composite output signal from the comparators is converted to a d.c. level which is compared to a fixed reference potential related to the duty cycle of a typical input signal. The comparator output signal is integrated and the peak value of which is stored by a peak detector. In the preferred embodiment the peak value is converted into digital form by an analog-to-digital converter.

Abstract: A surface activated multishot survey tool utilizes a dampened magnetic compass movably positioned within a probe to determine the direction of a borehole. Lamps in the probe are operable to light the face of the compass. A lens projects the image of the compass onto a movable film strip. An electrical cable is connected to the probe and is used to pass a current to the lamps and provide selective operation of the tool from the surface of the borehole. Electrical connectors are provided at each end of the probe so that the probe may be inverted within the borehole to accommodate surveys in which the angle of the borehole is greater than that at which the compass will operate without error. Because connectors are located at both ends of the probe, electrical current passes around the magnetic compass, thus creating a magnetic field about the compass.

Abstract: A combination of magnetics and a special geometric environment is employed to distinguish whether an instrument is positioned within a pipe formed of magnetizable or non-magnetizable material, and is the basis, in part, for a method and an apparatus used in controlling picture taking at the bottom of a well bore. A coil is energized repetitively in a circuit in which the voltage across the coil, or the current that flows through the coil, can be measured. Whether the coil is in a magnetic or non-magnetic environment is determined by the magnitude of the change in coil voltage or current.

Abstract: An improved well logging method and apparatus is provided for more reliable and accurate detection of corrosion in subsurface well casing. Method and apparatus are described for measuring the density of the flux field established inside the casing due to galvanic current flow longitudinally within the casing. A subsurface instrument housing a plurality of flux gates traverses the interior of the casing measuring the flux density within the casing. As the instrument comes proximate a corrosion location there will be detected a change in flux density due to current flowing from the casing into the formation. The detected change is transmitted to a surface location to provide an indication of the location and depth of corrosion.

Abstract: Casing inspection apparatus and method are disclosed for determining defects and other anomalies in ferromagnetic oil well casing. The inspection apparatus utilizes a pair of coaxial transmitter coils for generating an alternating magnetic field in the casing thereby inducing circumferential currents in the casing wall. These circumferential currents and the magnetic field associated with the currents are perturbed by corrosion, holes, and other anomalies both inside and outside the casing wall. Differential receiver coils are urged in proximity with the casing wall to generate a differential receiver signal in response to such perturbations in the magnetic field. The differential receivers are provided with three coils serially connected and having N, 2N and N winding turns respectively. The windings of the coils are disposed in adjacent relationship to one another and wound in a direction opposite to the adjacent winding.

Abstract: An electromagnetic thickness tool is disclosed to produce a measurement of the wall-thickness of a ferromagnetic casing corrected for the effects of casing permeability. First apparatus provides an uncorrected thickness signal proportional to the thickness of the casing uncorrected for the effects of casing permeability. A second apparatus provides a permeability signal representative of the permeability of the casing. A signal processor uses the mathematical square root of the permeability signal as a correction factor for the uncorrected thickness signal for generating the corrected value. The second apparatus, responsive to a signal proportional to the magnitude of the inside diameter of the casing, corrects the permeability signal for the effects of casing inside diameter.

Abstract: Instrument for locating the depth of the lower end of a mild steel or cast iron well casing or a plastic casing attached to a mild steel well screen has an elongated weighted body portion containing one fixed magnet engageable with the casing and located at the upper end of the instrument. A radially movable magnet is encapsulated in the body of the instrument, preferably at a lower location than the fixed magnet. The movable magnet is normally magnetically biased toward the casing when a ferrous casing or well screen is present adjacent the instrument but is magnetically urged toward the ferrous metal contacts of a switch located internally of the instrument to actuate a signal device when there is no ferrous casing or well screen adjacent the movable magnet. The instrument is suspended in the casing by a cable containing electrical conductors attached to the switch contacts and to the signal device.

Abstract: An electromagnetic sensing system is disclosed for sensing the linear distance between two elements and generating a signal related to the distance. The sensing system utilizes a magnetized initiator as one element, and a magnetic fluxgate as the second element. The magnetic fluxgate creates a flux "window" by locating a biased toroidal saturating coil inside a sensing coil, both of which are located inside a non-magnetic sleeve having an opening or "window" to magnetic flux, with the window being focused on the initiator magnet.

Abstract: Inspection apparatus adapted to be propelled through a pipeline. Means are provided to establish a circumferentially directed flux field in wall of pipe, and longitudinally extending flexible fins or flaps of elastomeric material curve outwardly from apparatus to resiliently hold flux leakage detection means against wall of pipe. Means responsive to axial movement of apparatus imparts helical movement of apparatus. Apparatus is readily adapted to inspect pipelines of different sizes.