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 borehole survey instrument is provided which includes a meniscus type floating compass member for indicating azimuth and inclination. A light source is disposed below the indicia for illuminating the indicia upwardly through the liquid in which the compass member floats and a novel lens system is provided for focusing the image of the illuminated compass member upon a film disposed below the compass member and for transmitting illumination to the compass member. The compass member is mounted on a centering post which is of minimum diameter consistent with the required rigidity and which permits high angle compass members to be utilized to indicate angles approaching ninety degrees. In a preferred embodiment of the present invention, the lens system has a refractive index closely matching that of the liquid surrounding the floating compass member to minimize reflection or refraction at the inner face therebetween.

Abstract: A borehole survey instrument is provided having a meniscus type floating compass member with indicia thereon for indicating azimuth and inclination. A light source is disposed below the indicia for illuminating the indicia upward through the liquid through which the meniscus type floating compass member floats. A lens system is provided for focusing the image of the illuminated compass member upon a film disposed below the compass member. This arrangement permits the centering post for the compass member to be of minimum diameter consistent with rigidity requirements and permits a high angle compass member to indicate angles of inclination approaching ninety degrees. A multiple light bulb light source is utilized and each light bulb is mounted in a manner which permits a single light bulb to illuminate the entire compass member.

Abstract: A borehole survey instrument and control circuitry are described. The borehole survey instrument includes indicators for measuring angle of deviation from the vertical and angle of deviation from magnetic north and a photographic recording means for recording the output of the indicators at selected times. A lighting system is utilized in conjunction with the photographic recording means to expose photographic film and a novel time control circuit is utilized in conjunction with the lighting system to alter the length of time of illumination in accordance with the operativeness of individual bulbs within the lighting system. In this manner, the failure of one or more bulbs within the lighting system will not substantially affect the amount of illumination to which the film in the photographic recording means is exposed.

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.