Abstract: A self-propelling apparatus for well logging tools includes a housing which is secured to the housing of a well logging tool and which defines a cylinder. A piston is slidably received in the cylinder, and a powder charge is mounted in the housing for electrical actuation. The cylinder is initially filled with a weighted fluid to establish a negative buoyancy whereby the well logging tool moves downwardly in a well to effect a logging operation. Upon completion of the well logging operation, a signal from the well logging tool actuates the powder charge whereby the piston forces the weighted fluid out of the cylinder and thereby establishes a positive buoyancy. This positive buoyancy together with the flow of the weighted fluid and the flow of gases resulting from the burning of the powder charge out of the housing combine to propel the well logging tool upwardly. At the top of the well the apparatus is siezed by latching apparatus and is retained thereby for subsequent retrieval.