Abstract: The invention is a method of determining a free point in stuck drill pipes, comprising the steps of: a. measuring a first magnetic permeability (?1) based on a time-induced decay of the electromagnetic field generated by application of an electric current pulse to the unextended pipe (l0); b. applying a force to the pipe to extend the pipe (l1); c. measuring a second magnetic permeability (?2) of the extended pipe (l1); and d. comparing the first and second magnetic permeabilities (?1 and ?2) along the drill string to determine the free point based on the change of magnetic permeability.

Abstract: A gap collar for an electromagnetic communication unit of a downhole tool positioned in a wellbore is provided. The downhole tool communicates with a surface unit via an electromagnetic field generated by the electromagnetic communication unit. The gap collar includes a first collar having a first end connector and a second collar having a second end connector matingly connectable to the first end connector. The gap collar further includes a non-conductive insulation coating disposed on the first and/or second end connectors, and a non-conductive insulation molding positioned about an inner and/or outer surface of the collars. The insulation molding moldingly conforms to the shape collars. The connectors are provided with mated threads modified to receive the insulation coating. Measurements taken by the downhole tool may be stored in memory, and transmitted to the surface unit via the electromagnetic field.

Abstract: An improved method of permanently marking the location of a tubular joint, the method including creating a cavity into the end surface of one of the tubular ends that are to be joined by a forge weld or screw thread connection, inserting a marker into said cavity and subsequently joining the tubular ends.

Abstract: A method and a downhole telemetry system a downhole telemetry system using discrete multitone modulation for transmitting a data stream over a plurality of transmission modes is provided. The downhole telemetry system includes a downhole transmitter, a cable, and a surface receiver. The downhole transmitter is configured to transmit the data stream over the plurality of transmission modes. The surface receiver is coupled to the downhole transmitter via the cable and is configured to combine signals from each of the plurality of transmission modes to obtain the data stream transmitted by the downhole receiver. The method includes receiving a plurality of signals over the plurality of transmission modes from a downhole package, and may further include combining the plurality of signals to form at least one data stream.

Abstract: A well logging system is disclosed having an improved speed correction apparatus and method. One embodiment comprises a logging sonde, a wireline cable, a distance sensor, a tension sensor, and a surface computer. The logging sonde moves through a wellbore while making logging measurements of the formation around the wellbore. The sonde includes an accelerometer to measure acceleration of the logging sonde. As the wireline cable is reeled in on the surface, the distance sensor detects the length of wireline cable that is retrieved. The tension sensor measures the tension in the wireline cable. The surface computer receives measurements from the accelerometer, the distance sensor, and the tension sensor, and determines intervals in which the logging tool is stuck. At least in part, this is done by finding “slow” intervals in which the wireline cable is stretching at about the same rate that the wireline cable is being reeled in.

Abstract: Method and systems for reducing effects of magnetic field interference that may interfere with a magnetic field signal generated at or near an underground object, where the magnetic field signal is used to monitor the location of the underground object. At least two different moving averages of a plurality of samples that are representative of a detected magnetic field signal strength are produce. Each of the different moving averages is a moving average of a different number of the plurality of samples. A respective quality metric (e.g., variance) is then determined for each of the different moving average. One of the moving averages is selected based on the determined quality metrics. Further signal processing is then performed using the selected moving average. For example, the selected moving average is used to monitor the location of the object.