Self-propelling apparatus for well logging tools

A self-propelling apparatus for well logging tools comprising:

• a housing including means for attachment to a well logging tool;
• the interior of the housing defining an elongate cylinder for initially receiving a quantity of liquid and thereby establishing an overall negative buoyancy for the self-propelling apparatus and the well logging tool attached thereto;
• a piston initially positioned at one end of the cylinder;
• vent means communicating between the opposite end of the cylinder and the exterior of the housing wherein said vent means are outwardly directed;
• an explosive composition mounted within the housing;
• means responsive to a predetermined signal for igniting the explosive composition and thereby driving the piston from its initial position to the opposite end of the housing to expel the liquid from the cylinder through said vent means and thus establish an overall positive buoyancy for the self-propelling apparatus and the well logging tool connected thereto;
• and
• said means for igniting the explosive composition is further characterized by means for receiving a signal from the well logging tool connected to the housing.

A self-propelling apparatus for well logging tools comprising:

• an elongate, cylindrical housing having means at one end thereof for attachment to a well logging tool;
• said housing defining in the interior thereof an elongate cylinder for initially receiving a quantity of liquid to provide an initial overall negative buoyancy for the self-propelling apparatus and the well logging tool;
• piston means initially positioned at one end of the cylinder in the housing;
• said piston means including sealing means engaging the walls of the cylinder to effect a seal therewith;
• vent means communicating with the opposite end of the cylinder and extending outwardly to the exterior of the housing;
• said housing further including a chamber communicating with the cylinder and extending from said one end thereof;
• a quantity of material mounted in the chamber of the housing and adapted for ignition to provide a substantial quantity of highly pressurized products of combustion;
• means for igniting said material in response to a predetermined signal and thereby driving the piston from said one end of the cylinder to the opposite end thereof to expel the liquid from the cylinder through said vent means and thereby provide an overall positive buoyancy for the self-propelling apparatus and the well logging tool;
• and
• electrical ignition means for initiating combustion of the material in the chamber of the housing;
• actuation means for activating the electrical ignition means;
• switch means for normally preventing operation of the electrical ignition means under the action of the actuation means;
• and
• input means for causing the switch means to electrically interconnect the actuation means and the ignition means and thereby effect ignition of the material.

In combination:

• a well comprising a tubular string having a well fluid therein;
• a well logging tool for movement through the well fluid in the well to carry out a well logging operation;
• said well logging tool having a housing;
• a self-propelling apparatus for controlling the movement of the well logging tool through the well fluid in the well;
• said self-propelling apparatus having a housing including means for connection to the housing of the well logging tool;
• the housing of the self-propelling apparatus defining a cylinder for initially receiving a quantity of liquid and thereby causing the self-propelling apparatus/well logging tool assembly to have a negative buoyancy relative to the well fluid in the well;
• means in the self-propelling apparatus responsive to a predetermined signal for expelling the liquid from the cylinder of the self-propelling apparatus and thereby causing the self-propelling apparatus/well logging tool assembly to have a positive buoyancy relative to the well fluid in the well;
• and
• latching apparatus mounted at the top of the tubular string of the well for receiving and retaining the buoyant self-propelling apparatus/well logging tool assembly, wherein said latching apparatus comprises a plurality of spring loaded jaws positioned at spaced points around the periphery of the tubular string of the well.