Abstract: A large-dip-angle self-leveling device is provided. The device comprises a mounting base platform arranged on a mounting stand column and a support cylinder connected with the mounting base platform. A leveling plate is arranged at the top of the mounting base platform, and a leveling platform is arranged on the leveling plate. A spirit bubble indicator and a control circuit board are arranged on the leveling platform. A connecting rod of balance weight is arranged in the support cylinder, one end of the connecting rod of balance weight is connected with the leveling platform, and the other end is connected with a balance weight. A four-core cable penetrates through the connecting rod of balance weight and the balance weight. Observation windows are symmetrically arranged at the lower part of the support cylinder. A melting pool is arranged at the bottom in the support cylinder.

Abstract: Aspects of the subject technology relate to a sensor for a downhole tool. The downhole tool can include a collar and a sensor. The sensor can be secured to the collar for measuring one or more operational characteristics of the downhole tool during operation of the downhole tool. The sensor can include a substrate. The sensor can also include a plurality of strain gauges disposed on the substrate. The plurality of strain gauges can be configured to measure axial strains and torsional strains on the collar for measuring the one or more operational characteristics of the downhole tool.

Abstract: A centraliser comprises a mandrel, a first support member, a second support member, and a plurality of arm assemblies connected between the first and second support members. Each arm assembly comprises a first arm pivotally connected to the first support member at a first pivot axis and a second arm pivotally connected to the second support member at a second pivot axis, and the first and second arms pivotally connected together at a third pivot axis. The mandrel comprises a plurality of facets spaced apart around an outer surface of the mandrel to rotationally key the first and/or second support member to the mandrel, and each arm assembly is arranged so that the third pivot axis is located on a first side of a plane coincident with a central axis of the device and the first and second pivot axes are located on an opposite second side of the plane.

Abstract: The pure mechanical well deviation wireless measure-while-drilling and mud pulse generation device includes an outer cylinder and an inner cylinder coaxially arranged inside the outer cylinder; an inner flow channel is formed inside the inner cylinder, and an outer flow channel is formed between the inner cylinder and the outer cylinder; a flow control valve and a hydraulic turbine are arranged in the inner flow channel, and the flow control valve is located at an upstream section of the hydraulic turbine. The device further includes a signal generation base and a rotary stopper. An overflow hole is formed on the signal generation base and arranged in the annular outer flow channel, and the rotary stopper can periodically shield the overflow hole. The inclinometer includes the pure mechanical well deviation wireless measure-while-drilling and mud pulse generation device, an inclinometer outer cylinder and an eccentric rotary column.

Abstract: A centralizer operable to connect with and centralize a downhole tool within a tubular string within a wellbore and to facilitate reception of electromagnetic signals transmitted through the Earth. The centralizer has a body, a first contacting member electrically connected to the body and extending radially away from the body such that the first contacting member contacts an inner surface of the tubular string to electrically connect the tubular string to the body, and a second contacting member electrically insulated from the body and extending radially away from the body such that the second contacting member contacts the inner surface of the tubular string to centralize at least a portion of the body within the tubular string.

Abstract: A tubing rotator and a drive therefor. The tubing rotator includes an input shaft to a tubing rotator gear; an electric motor including an output shaft; and a plurality of worm drives arranged in series and configured to (i) receive input from the electric motor and (ii) output torque to the input shaft of the tubing rotator. The worm drives may be identical speed reducers, such as with an input to output reduction ratio of from 25:1 to 40:1.

Abstract: The invention relates to an inertial navigation system for a carrier comprising a core comprising gyroscopic sensors making it possible to determine the angular velocity thereof according to three axes defining a reference trihedron, two of the axes defining a reference plane and the third axis being at right angles to this plane. The device comprises command and control means making it possible to rotate the core about the third axis and to determine the direction of the geographic north on the basis of the information supplied by the gyroscopic sensors and by an accelerometer placed in the reference plane; the rotation of the core being performed with a period for which the value of the Allan variance of the stability error of the gyroscopic sensors is lower than a given value guaranteeing the accuracy with which the direction of the geographic north can be known.

Abstract: Methods and apparatuses for calibrating attitude-independent parameters of a 3-D magnetometer are provided. A calibration method includes storing and updating data related to a N×9 matrix T and a N×1 matrix U extended for each measurement with an additional row and an additional element, respectively, the additional row and the additional element being calculated based on values measured by the 3-D magnetometer for the respective measurement. The method further includes calculating analytically (1) a symmetric non-orthogonal 3×3 matrix D representing scaling and skew of the 3-D magnetometer measured values and (2) a vector b representing bias of the 3-D magnetometer measured values, using the stored data and a singular value decomposition (SVD) method.

Abstract: A method includes coupling a strain gauge to a tubular member, and positioning the tubular member in the wellbore such that the tubular member is placed under bending stress by a curvature or deviation in the wellbore. The method also includes measuring bend on the tubular member with the strain gauge in at least one plane and determining one or more of the magnitude or orientation of the curvature of the wellbore based on an output of the strain gauge.

Abstract: Various embodiments of methods and apparatus for detecting a change in an orientation of a portion of a structure. In some embodiments, the apparatus includes a processor, an energy storage unit, a location reporting unit, a wireless communication module and one or more inclination sensors. In some embodiments, each of the one or more inclination sensors is configured to measure inclination by measuring an orientation of the each of the one or more inclination sensors relative to a gravitational acceleration vector.

Abstract: A downhole device is provided that is intended to be co-located with an optical fiber cable to be found, for example by being fixed together in the same clamp. The device has an accelerometer or other suitable orientation determining means that is able to determine its positional orientation, with respect to gravity. A vibrator or other sounder is provided, that outputs the positional orientation information as a suitable encoded and modulated acoustic signal. A fiber optic distributed acoustic sensor deployed in the vicinity of the downhole device detects the acoustic signal and transmits it back to the surface, where it is demodulated and decoded to obtain the positional orientation information. Given that the device is co-located with the optical fiber the position of the fiber can then be inferred. As explained above, detecting the fiber position is important during perforation operations, so that the fiber is not inadvertently damaged.

Abstract: An alignment apparatus for aligning drilling machines, the alignment apparatus comprising a casing and mounting means. The mounting means allowing, in use, for a true north seeking sensing means to be aligned with the drilling machinery to be aligned. The alignment apparatus being capable of displaying azimuth and pitch information to a user, so that the drilling machinery can be aligned as required.

Abstract: Exemplary embodiments provide a prefabricated modular shower enclosure, including a base with a plurality of engagement feature along a peripheral surface of the base, a plurality of alignment supports, and a surround panel. In some embodiments, at least one alignment support is positionable in a preselected relationship relative to the engagement features of the base, and the alignment supports are configured to be independently made square relative to the base. Additional exemplary embodiments provide a prefabricated shower enclosure, including a base with a plurality of engagement feature along a peripheral surface of the base, and a plurality of surround panels that engage the base. The modular shower enclosure reduces installation time and complexity by using components that are fabricated and cut to size offsite prior to installation at a job site.

Abstract: A magnetic field sensor generates signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system. A reader coupled to the magnetic field sensor determines a center offset based on received signal components, adjusts the received signal components based on the determined center offset, and applies Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters. The reader generates calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters.

Abstract: A subsea fluid storage system comprising a soft bladder disposed within a pressure balanced reservoir, a rotatable piston, and a piston rotator which rotates and twists the rotatable piston as it travels along a predetermined axis within the pressure balanced reservoir, predictably and repeatabley collapses the soft bladder when the rotating piston cooperatively travels about the piston rotator, twisting the soft bladder as the rotating piston moves along the predetermined axis, collapsing the bladder inward and thereby emptying the bladder of fluid within the bladder. The piston's rotation pulls the soft bladder away from the pressure balanced reservoir's interior, thereby preventing the bladder's binding or pinching the pressure balanced reservoir's interior. In configurations, fluid is allowed to enter the pressure balanced reservoir via a valve until a balance is achieved between an interior and an exterior of the pressure balanced reservoir.

Abstract: Image matching on a pair of image data about images which are shot at different shooting positions is performed, and a point corresponding to the coordinates of a distance measurement point on the image shown by one image data of the pair is searched through the image shown by the other image data of the pair. The value of a parameter showing the attitude of an airplane (2) is corrected in such a way that the difference between the coordinates of the distance measurement point on the image shown by the other image data of the pair and the coordinates of the corresponding point which is searched for via the image matching becomes small, to estimate the attitude of the airplane (2).

Abstract: A gimbal sensor platform positionable in a tool body includes an inner gimbal and an outer gimbal. The inner gimbal is rotatably coupled to the outer gimbal, and the outer gimbal is rotatably coupled to the tool body. The inner and outer gimbals may each be rotated by an angular positioning device. A gyro or other sensor may be coupled to the inner gimbal. The gyro or other sensor may be reoriented by rotating the outer gimbal, the inner gimbal, or both.

Abstract: A torque anchor intended to block the rotation of a production string with respect to a casing of a well; the torque anchor comprising a body and anchor cassettes comprising a wheel having a circumference and a wheel spindle supporting said wheel, a contact point of the circumference of the wheel being intended to come into contact with the casing, an opposite point being arranged diametrically opposite the contact point. For each anchor cassette, the wheel is mounted on the end of the wheel spindle; a positioning angle comprised between 30° and 180° being defined between a first straight line passing through the center of the casing and the contact point and a second straight line passing through the center of the casing and the opposite point.

Abstract: A torque anchor intended to block the rotation of a production string with respect to a casing of a well, the torque anchor comprising a body, at least two supports mobile with respect to the body, wheels borne by the supports, the wheels being suitable for running on an inner face of said casing, at least one restraining device suitable for exerting a force on said wheels in order to anchor said wheels in said casing. Each restraining device comprises a set of springs suitable for acting on the set of said supports and a guide capable of guiding said set of springs; said guide being borne by said supports; said guide being mobile with respect to at least one support.

Abstract: An inclinometer for measuring a change in the inclination of a structure from a given initial position. The inclinometer comprises a frame, a pendulum and at least three distance-measuring device. The frame is rigidly connected to the structure such that the inclination of the frame has the same changes in inclination as the structure. The pendulum is freely suspended from the frame and comprises a first end attached to the frame and a freely moving opposite end. The distance-measuring devices at the frame have respective coplanar measuring axes converging at a single point. Each measuring device measures a change in the distance separating same from the pendulum.

Abstract: A system for remote monitoring of well operations. The system may include an alerts module positioned proximate a well, at least one well parameter sensor in communication with the alerts module, and a well operation control module in communication with the alerts module. The system may further include a remotely positioned well monitoring station in communication with the alerts module, and a user terminal in communication with the well monitoring station.

Abstract: A hyperelastic, soft microfluidic film measures bending curvature using a novel non-differential mechanism. Disclosed embodiments of the elastomer-based solution allows for curvature sensing directly on a bending plane and thus eliminates limitations imposed by strain gauge factor (GF) and sensor thickness (Z). Due to soft lithography microfabrication and design methods the disclosed curvature sensors are elastically soft (modulus 0.1-1 MPa) and stretchable (100-1000% strain). In contrast to existing curvature sensors that measure differential strain, embodiments of the present invention measures curvature directly and allows for arbitrary gauge factor and film thickness. Moreover, the sensor is composed entirely of soft elastomer (PDMS or Ecoflex® and conductive liquid (eutectic gallium indium, (eGaIn)) and thus remains functional even when stretched to several times its natural length.

Abstract: In one aspect an apparatus for determining a distance between a first borehole and a second borehole during drilling of the second borehole is disclosed that in one embodiment includes a magnet on a drilling tool that rotates in the second borehole to induce a primary magnetic field in a magnetic object in the first borehole, a substantially stationary sensor on the drilling tool that detects a secondary magnetic field from the magnetic object responsive to the induced primary magnetic field, and a controller that determines the distance between the first borehole and the second borehole from the detected magnetic field.

Abstract: Inclinometer and directional field sensor readings can have gain, offset, and non-orthogonality errors, as well as reference alignment rotation errors. When a series of readings are taken by a three axis sensor with a variety of different orientations, the resulting dataset looks like a perfect hypothetical sphere in the absence of any errors; with errors as mentioned above the dataset looks like an offset, rotated, ellipsoidal quadratic surface. This invention provides a simple method of removing the above errors from a tilt reference device. A disclosed algorithm is divided into two distinct components: the ellipsoidal quadratic surface component, which covers gain, offset, and axis misalignment; and the rotation component, which covers rotation relative to a set of reference axes. The solution presented here addresses both components combined, or separated and for inclinometers, magnetometers and rate sensors.

Abstract: A spirit level has a first inclination sensor, at least one second inclination sensor, and a display to represent an inclination for the at least one second inclination sensor based on an inclination for the first inclination sensor. The display may represent the inclination for the at least one second inclination sensor as an inclination relative to the inclination at the first sensor. At least one of the inclination sensors may have a changing inclination. In this case, the display represents the inclination for the at least one second inclination sensor based on the changing inclination. The inclination sensors may be movable with respect to a remainder of the spirit level. In this case, the inclination sensors may be connected to the remainder of the sprit level with a cable or high frequency radio links.

Abstract: A miniature directional indication sensor system capable of operating at elevated temperature. A directional indication sensor system is less than 1 inch in diameter and 7 inches in length. The directional sensor system provides angle measurement in applications from which current larger directional sensors are barred. The present invention provides increased shock and vibration resistance. The chassis of the present invention has an high resonant frequency, or “Q”. The present invention is implemented with power supply, sensor drive and sense circuits in thick film or multi-chip module electronic assemblies. The thick film or multi-chip module electronics assemblies also contribute to the increased shock and vibration resistance. Sensor drive and sense functions may be implemented in one or more application specific integrated circuits and integrated with multi-chip module electronics assembly.

Abstract: A method of deriving the true magnitude of the terrestial magnetic field in the direction of the longitudinal axis of a borehole at a region of the borehold occupied by an instrumentation package equipped with magnetic vector measuring means for measuring the lateral magnetic vectors Bx and By and further equipped with gravitational vector measuring means for measuring each of the three gravitational vectors Gx, Gy, and Gz.The method comprises the steps of performing said measurements of the magnetic vectors and the gravitational vectors and from said vector measurements solving the equation:Bze=(Bve.Ge-Bx.Gx-By.Gy)/Gzwhere BVe is the vertical component of the terrestial magnetic field at the location of the borehole, and Ge is the terrestial gravity field. The terrestial gravity field Ge may be derived as the square root of the sum of the individual squares of the individual gravity vectors Gx, Gy and Gz, according to the equation:Ge=(Gx.sup.2 +Gy.sup.2 +Gz.sup.2).sup.1/2.

Abstract: A method is proposed for better determining the azimuth and inclination of a borehole in which a priori information regarding the magnitude of the earth's gravitational field strength, its magnetic field strength and direction are utilized to constrain the measured components of the earth's gravitational and magnetic field vectors. The constrained fit method adjusts the accelerometer and the magnetometer tri-axis measurements to optimize agreement between the measured data and the a priori magnetic and gravity field strengths and the magnetic dip angle. The adjustment that is selected is that which produces the least increase in the statistical measure .chi..sup.2.

Abstract: The sensor comprises a body defining a closed chamber which is partially filled with electrically conductive liquid. A main electrode and first and second auxiliary electrodes extend within the chamber in such a way that a variation in the inclination of the body from a predetermined position causes a corresponding variation in the electrical resistance between each auxiliary electrode and the main electrode. The monitoring circuit for the sensor comprises a generator which applies square-wave signals to the auxiliary electrodes in counterphase, and a detector/amplifier which is synchronized with the generator and samples the signal taken from the main electrode in the sensor.

Abstract: A method is presented, for use in borehole drilling, for correcting errors in azimuth determination resulting from variations in the earth's magnetic field to which a measuring instrument is exposed. The method distinguishes between variations in the earth's magnetic field caused by the drillstring and variation caused by external sources, and the method corrects only for errors caused by the drillstring. If the error is caused by the drillstring, an azimuth correction is made based on dip angle data, thereby reducing errors caused by scale factor variations since dip angle is a ratio quantity of magnetic field components.

Abstract: An instrument for monitoring the direction of a borehole comprises an elongate casing having its longitudinal axis coincident, in use, with the axis of the borehole, an outer gimbal pivotally mounted within the casing with its pivot axis coincident with the longitudinal axis of the casing, a gyroscope unit mounted in the outer gimbal, a torque motor and a gravity sensor unit. At the beginning of a run the instrument is positioned at the mouth of the borehole. The rate of rotation about an axis transverse to the outer gimbal axis is then sensed by the gyroscope unit, and the outer gimbal is slewed by the torque motor in dependence on the sensed rate so as to align the transverse axis along an East/West direction. The instrument is then moved along the borehole and the rate of rotation about the outer gimbal axis is continually sensed by the gyroscope unit, the outer gimbal being torqued by the motor in dependence on the sensed rate to stabilize the outer gimbal about its axis.

Abstract: A method of determining the orientation of a surveying instrument in a borehole from measurements of the earth's gravitational and magnetic fields wherein the azimuth angle is calculated directly without correcting an apparent azimuth. Those measurements are used to calculate the borehole axial magnetic component at each orientation of the surveying instrument in the borehole, and the borehole axial magnetic component is used, along with those measurements, to directly calculate the proper azimuth angle. In a preferred embodiment, measurements are taken at a plurality of orientations in the borehole and the borehole axial magnetic component is calculated in simultaneous equations and then compared to insure the accuracy of the azimuth computation at each orientation. The orientations are preferably non-colinear.

Abstract: A bore hole navigator utilizing a two axis directional gyro on the inner frame of the navigator and a single axis accelerometer on the outer frame is disclosed. This allows the inner frame of the navigator and thus the entire navigator to be smaller in diameter, both because of the removal of the acceleration axis to the outer gimbal and because the electrolytic level sensor, if used, is much smaller than a single axis accelerometer. The overall smaller diameter is maintained by using a belted design wherein the gyro/electrolytic level sensor, the inner frame torquer/gear and the inner frame resolver are connected in series along the length of the navigator, with a high gear reduction ratio on the inner frame torquer providing a positive drive within a smaller diameter. This configuration, together with unique calculation algorithms allows smaller diameter and deeper holes to be surveyed.

Abstract: A borehole survey instrument has a probe with a polarized light system for transmitting a signal representing the angular orientation of the probe to the surface. Light from a source in the probe is directed through a polarized filter with an axis of polarization orthogonal to the longitudinal axis of the probe. The polarized light beam is transmitted to the surface through an optical fiber light conduit. The angle of polarization is detected with a rotating polarizing filter and provides a measure of the probe orientation. In surveying a borehole, azimuth is determined from inclinometer measurements. The probe orientation in vertical sections of the borehole is measured by the polarized light system. Two measures of borehole azimuth are combined, providing an improved measure of azimuth in boreholes near vertical and near horizontal.

Abstract: A borehole survey instrument has a probe with a polarized light system for transmitting a signal representing the angular orientation of the probe to the surface. Light from a source in the probe is directed through a polarizing filter with an axis of polarization orthogonal to the longitudinal axis of the probe. The polarized light beam is transmitted to the surface through an optical fiber light conduit. The angle of polarization is detected with a rotating polarizing filter and provides a measure of the probe orientation. In surveying a borehole, azimuth is determined from inclinometer measurements. The probe orientation in vertical sections of the borehole is measured by the polarized light system. Two measures of borehole azimuth are combined, providing an improved measure of azimuth in boreholes near vertical and near horizontal.

Abstract: A borehole survey apparatus including(a) angular rate sensor means having a sensitive axis,(b) tilt sensor means,(c) a rotary drive operatively connected to said (a) and (b) sensor means to rotate same about an axis extending generally in the direction of the borehole,(d) and circuitry operatively connected with said (a) and (b) sensor means to determine the azimuthal direction of tilt of the borehole at a first location therein, said (a) sensor means also connected in feedback relation with the drive whereby the sensitive axis of the (a) sensor means is maintained at a predetermined orientation relative to horizontal during travel of said apparatus in the borehole relative to said first location, and whereby changes in borehole alignment during said travel may be determined.

Abstract: The invention relates generally to mapping or survey apparatus and methods, and more particularly concerns efficient transmission of survey signals or data from depth level in a borehole or well to the well surface, for analysis, display or recordation; further it concerns efficient transmission of command data from a surface computer unit to the survey tool at depth level in a borehole or well for control of instrumentation operating modes, operating characteristics, or diagnostic purposes; and further it concerns supply of DC power downwardly to the instrumentation via a wireline by which such command signal and survey data or signals may be transmitted upwardly or downwardly respectively.

Abstract: Apparatus and a method for detecting deflections along the length of a pipeline. A plurality of measurements of inertial attitude are made along the length of the pipeline over time by means of apparatus, including sensors, associated with a pipeline pig. Thereafter, by comparing a time sequence of such measurements, points of flexure are accurately located and identified.

Abstract: A logging telemetering system comprising a toroidal coupled telemetry apparatus including a primary winding carrying bore hole data, wrapped around at last one torroid core mounted within a drill collar. The toroid core is further wrapped with at least one secondary turn which is connected to the drill collar for enhancing the efficiency of inducing a current carrying the borehole data in the drill string for transmission to the surface. One half turn of the secondary winding is provided by an insulated portion of the drill collar, and the balance of the secondary winding is composed of an electrically conductive strap wound around the toroid core.

Abstract: A sensor (16) is affixed to a piece of rotatable equipment (10). The sensor has a rolling member (26) freely moveable within a cage member (18). In operation, the rolling member (26) contacts electrically conductive surfaces (28,30) disposed about the interior of the cage member. By determining which particular pair of surfaces are currently in contact with the rolling member, the orientation of the cage member with respect to the horizontal is known. The preferred embodiment utilizes a resistor network (34) and an electrical measuring device (48) for making this determination.

Abstract: A well mapping apparatus comprises:(a) a magnetic field sensing device whose output is proportional to a local magnetic field vector,(b) an acceleration sensing device whose output is proportional to a local gravity vector,(c) the devices supported for rotation about a common axis, in a borehole,(d) the outputs being usable in the determination of azimuth and inclination of the borehole.

Abstract: A borehole survey method employs a first sensor for measuring angular rate, and a second sensor or sensors for sensing tilt, and a rotary drive for the first and second sensors, and includes the steps:(a) operating the drive and the first and second sensors at a first location in the borehole to determine the azimuthal direction of tilt of the borehole at such location,(b) then traveling the first and second sensors and the drive lengthwise of the borehole away from the location, and operating the drive and at least one of the first and second sensors during such traveling to determine changes in borehole alignment during such traveling.

Abstract: A downhole digital power amplifier comprises a device which, through digital means, provides a sinusoidal, variable frequency, variable power and variably phase-shift modulated output for the transmission of data from a downhole sensor arrangement to an uphole receiver. Selection and variation of frequency, power and modulation are made through digital inputs. The device provides these functions at extra low frequencies (ELF) low-to-high power output, and varying phase-shift keying.

Abstract: A borehole mapping and/or navigational instrument includes a carrier movable lengthwise in the borehole; structure on the carrier defining an axis of rotation; and a tilt sensitive device rotatable about the axis of rotation, that device having a tilt sensitive axis with components along the axis of rotation and along perpendiculars to that axis. One or more angular rate sensors may be provided to be rotatable about the axis of rotation.

Abstract: The invention concerns efficient transmission of borehole survey signals or data from depth level in a borehole or well to the well surface, for analysis, display or recordation; further it concerns supply of DC power downwardly to the instrumentation via the same wireline via which such survey data or signals are transmitted upwardly.

Abstract: A transducer for sensing the angular position or rate of change of displacement of a housing of a borehole survey instrument with respect to a reference position includes a rotor magnetically suspended within a stator which is in turn secured to the housing. The rotor is constrained by the magnetic suspension to rotate about a single axis relative to the stator. A frame of reference is established for the transducer, against which subsequent measurements are compared. Optical sensing means are included for sensing the movement of the rotor about the axis of motion to develop an indication of the angular position or rate of change of position of the housing.

Abstract: An apparatus and its use for measuring the differences in gravity at spaced locations in a wellbore. The apparatus includes first and second gravity measuring devices mounted at spaced vertical positions from each other and encapsulated for movement through a wellbore. A first electrical control current, proportional to the force of gravity acting upon the first gravity measuring device, is provided as a bias current to a second electrical control current. The second electrical control current is indicative of differences in gravity forces detected by the first and second gravity measuring devices, thereby providing a gravitational gradient reading.

Abstract: The present invention relates to a program controlled apparatus for providing rapid calibration and update of sensor parameters in a push drill guidance apparatus which is remotely controllable from microprocessor circuitry. A special calibration program is set into non-volatile memory for coaction with the control processor to compute sensor parameters for storage and recall during normal programmed guidance operation.

Abstract: An instrument including a gyroscopic rotor mounted to precess about a predetermined axis in response to pivotal movement of the rotor about a sensing axis, with the rate of precession being measured and being utilized to determine the amount of said pivotal movement above the sensing axis. Two or more such rotors precessing about different axes can respond to different components of the earth's rotational movement, or to other component movements or torques. Differences in the rates of precession of the two rotors indicate the relative strengths of the corresponding components of the earth's movement, and afford a basis for deriving an indication of azimuth.

Abstract: A surface activated multishot survey tool utilizes a dampened magnetic compass movably positioned within a probe to determine the direction of a borehole. Lamps in the probe are operable to light the face of the compass. A lens projects the image of the compass onto a movable film strip. An electrical cable is connected to the probe and is used to pass a current to the lamps and provide selective operation of the tool from the surface of the borehole. Electrical connectors are provided at each end of the probe so that the probe may be inverted within the borehole to accommodate surveys in which the angle of the borehole is greater than that at which the compass will operate without error. Because connectors are located at both ends of the probe, electrical current passes around the magnetic compass, thus creating a magnetic field about the compass.