Abstract: In a preferred embodiment of the new and improved well tool that is described herein, a set of alternate outer tool housings are respectively arranged for carrying a common inner assembly having one or more temperature-sensitive devices. The new and improved set of alternative housings includes a first tubular housing having a solid wall of a steel of sufficient strength and thickness to withstand a predetermined pressure and a second tubular housing having inner and outer tubular members coaxially arranged to provide a hollow wall having substantially equal external and internal diameters as the first housing and which is formed of a steel of sufficiently greater strength than the steel in the first housing so that the second housing will have a design pressure rating about equal to the predetermined pressure.

Abstract: Well bore logging apparatus including electrical components cooling apparatus. An operating chamber and a heat sink chamber are incorporated. A heat transfer chamber encloses both operating chamber and heat sink chamber. A wicking material fills a portion of the transfer chamber to be in thermal connection with both operating chamber and heat sink chamber. The heat sink chamber contains a heat sink material. A heat transfer medium is contained in the heat transfer chamber which is vaporized by heat from the operating chamber, then condensed by the heat sink medium to be absorbed into the wicking member and transported through the wicking member by capillary action back to the operating chamber for revaporization. Heat transfer chamber is isolated from operating chamber.

Abstract: Apparatus for insulating enclosed electronic devices against damaging temperatures when used in deep, hot well bores. Includes a first vacuum chamber insulating means defined by outer casing of well-logging tool and inner casing. First vacuum chamber defines a components chamber to shield contents against the temperature in a well bore. A second vacuum chamber mounted within components chamber is defined by an outer tube and an inner tube. Outer tube has a thickened wall and is of material suited to serve as heat sink within components chamber. Second vacuum chamber defines detection chamber to shield contents against the temperature within components chamber. Thickened wall is undercut to define a thin wall adapted to function as a window for radiation to pass from an earth formation outside said logging tool into a radiation detector disposed within said detection chamber.

Abstract: Disclosed is an improved compensated density well logging apparatus which provides a mechanical linkage driven by an electric gear motor for extension of a thin cylindrical pad containing radioactive source and detection equipment exteriorly of the tool housing so as to penetrate the filter cake and eliminate or reduce the distorting effect of the filter cake and well bore fluid. A spring biased caliper arm is used to justify the tool and extended pad against the side of a well bore during measurement. The linkage supporting and positioning the caliper arm includes a pivot pin which extends exteriorly of the tool housing to engage two parallel aligned guide wheels riding in grooves formed exteriorly in the tool housing so as to reduce friction and prevent lateral movement of the linkage. This provides for a more accurate reading of the variable thickness of the filter cake and well bore diameter at varying depths within the well bore.