Abstract: Apparatus for downhole storage of an electrical conductor within a drill string in a borehole. The conductor is stored as a coil in a flexible storage means. The apparatus is desirably used to eliminate the short lengths of cable and the associated connectors which are normally added with each new section of drill pipe added to the drill string. Because the device is flexible, it may be used in deviated drilling.

Abstract: An improved apparatus to store an insulated electrical conductor cable in a overlapped configuration within a drill pipe includes a track attached to the drill pipe to guide a lower cable guide so that the overlapped portions of conductor cable will not snarl or twist during rotary drilling operations. To insure against entanglement, further restriction of rotation may be gained by additionally tracking the lower cable guide on a tensioned portion of the conductor cable which extends from a subsurface instrument package upwardly to an upper cable guide. A method for installing this improved apparatus is also disclosed.

Abstract: Abnormal drilling conditions are detected by monitoring mud volume of the mud system or rate of change of the mud volume. In one embodiment, makeup mud is automatically added to the system as solids are removed from the mud. Abnormal conditions are indicated by when the rate of makeup mud addition differs from the rate of solids removal. The mud system is maintained at a substantially constant volume by means of tanks specially constructed to provide a small mud/air interface.