Abstract: A pipe section is added to a drill string while an instrument and a flexible line leading to the instrument remain in the string. The effective length of the flexible line is increased in corresponding with the increase in length of the drill string by connection of the flexible line to a carrier by which the line is carried in a coiled condition occupying a distance longitudinally of the drill string shorter than the actual length of the line. The carrier is constructed to pay out the different turns of the coiled line successively from coiled condition to a straightened condition in a manner progressively increasing the effective length of the line. Preferably, the line is paid out from the carrier by pulling the carrier toward the outer end of the drill string while an inner end of the line is connected to the instrument in the string.

Abstract: Information is conducted upwardly from a location deep within a well by a transmitter which is located in the well and induces electrical currents in the surrounding earth formation. These currents are sensed at an upper location by readout equipment connected to two electrodes which are in electrical contact with the earth at spaced locations. One of the electrodes is at a subsurface location and is connected to the readout equipment by an insulated conductor. In offshore drilling situations, the specified subsurface electrode is at the very least located beneath the surface of the ocean or other body of water through which the well extends, and in most instances is preferably embedded within the earth formation under that body of water, and at a location spaced beneath the seabed.

Abstract: An inclination responsive device including a coil energized to produce a magnetic field extending along a normally vertical axis of the device, and a flux gate assembly adapted to respond to a horizontal component of that field upon tilting movement of the axis to an inclined non-vertical position, and to thereby produce an output which varies in response to changes in inclination. The flux gate assembly is desirably also responsive to the earth's magnetic field or another ambient field to also produce an output representing directional orientation of the device with respect to the ambient field.

Abstract: A hole in the earth is formed utilizing a drill string containing an instrument connected by a flexible conductive line to a unit at the surface of the earth. During intervals when the length of the drill string is being changed, as by addition of another pipe section to the outer end of the string, the connection between the flexible line and the surface unit is temporarily broken, so that the instrument and line can be left in the drill string while the section is added and for ultimate reconnection to the surface unit through the added section. A portion of the flexible line may be wound about an element in the string, to be unwound therefrom each time that the string is lengthened, to thereby correspondingly increase the effective length of the line.

Abstract: Methods and apparatus are provided for enabling an instrument and a connected flexible line contained in a drill string to be left in the string while a pipe section is being added to or removed from the string, to thereby avoid the inconvenience and loss of time normally involved in removing the instrument and flexible line from the string on each such occasion. This result is preferably accomplished by initially threading the flexible line at the surface of the earth through a series of extra pipe sections positioned at a storage location adjacent the well, so that each of these sections can then be successively moved from that location to a position of connection into the upper end of the drill string with the flexible line already installed in the added section.

Abstract: A flux gate unit for producing an output representing the directional orientation of the unit with respect to the horizontal component of the earth's magnetic field, and in which a saturable flux gate magnetic core structure is mounted for leveling movement relative to associated flux gate coil means, in a manner enabling maintenance of the core structure substantially continuously in level condition while avoiding the necessity for leveling movement of the flux gate coils, and thereby avoiding the necessity for connection of electrical leads to a movable part.