Abstract: An inertial borehole survey system is disclosed. The survey system of the present invention includes a probe suitable for insertion into a borehole. The probe includes a plurality of temperature sensitive inertial measuring instruments which are utilized to survey the borehole during the descent or ascent of the probe. Accuracy of these instruments is maintained by enclosing the instruments in a thermal insulating package and by providing a mass of isothermal heat absorbing material which exhibits a phase change at a temperature well above most ambient temperatures. In a preferred embodiment of the present invention, a heat absorbing material is utilized which exhibits a phase change at a temperature of 116.degree. F. The probe also includes a longitudinal air passage which permits ambient temperature air to be utilized to cool the isothermal heat absorbing material by passing air through the length of the probe.

Abstract: A system and method for surveying, with accuracies better than one foot per thousand feet of depth, very deep boreholes having the attendant small diameters, high temperatures and high pressures with very high accuracy. A downhole probe is used having a small diameter, less than about four inches. Three linear type accelerometers and at least two gyros to provide three sensitive axes are fixedly mounted at points spaced along the axis of an elongated, rigid, thermally conductive support member to form an instrument cluster. Signals from these instruments are then processed and transmitted serially over a conductor of a conventional wireline to the surface unit where a surface computer continuously computes and records the current position of the instrument.