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 for determining azimuth in well bore hole where the well is being drilled utilizing Measurement-While-Drilling (MWD) equipment, including gravitometer and magnetometer instruments in the presence of an adjacent well. Interference fields introduced by adjacent wells are modeled as a single or series of magnetic dipoles. The interference fields axial interference field IBz is tracked and a position determined where the IBz component is at its maximum, minimum or a zero value. The total magnetic field is then measured at that point and the magnetic inclination and therefrom, the azimuth may be determined. Alternately, the interference field in the x,y plane (IB(x,y)) may be tracked and a position determined where the IB(x,y) component is equal to a minimum, maximum or zero value. The azimuth may then be determined by an alternate numeric or curve fitting methods.

Abstract: The present invention provides a method for determining magnetometer errors during wellbore survey operations. It is capable of determining errors on up to three axes, with or without the use of an external reference measurement of the local magnetic field, and is capable of providing an accurate result using data from a minimum number of surveys. A model is used to correct the observed data and the corrected data are transformed from the tool coordinate system to a different coordinate system referenced to the earth. The difference between the corrected transformed data and reference data in the earth coordinate system is minimized to determine the model parameters. The present invention also provides a method for determining residual uncertainty in the measurements and for quality control of the measurements. By making the observations over a period of time, any deterioration of the sensors may be identified.

Abstract: Scraper for determining the position of pipelines with at least one scraper body and on the outer circumference of the latter are provided support elements for guiding in the pipeline, the scraper body containing a gyroscopic platform, as well as supply and processing means for measured results, characterized in that the scraper body is guidable by a combination of support elements under a defined, constant angle with respect to the pipe guidance axis, whereof a first part is radially rigid and a second part is radially resilient.

Abstract: An apparatus and method for orienting directional tools within a bore hole by recognizing and compensating for field biases brought about by ferromagnetic anamolies surrounding the bore hole, ferromagnetic casing strings and electrical/electronic tool components. The present invention includes the steps of measuring the magnetic field within a bore hole before casing strings are put in place and again measuring the magnetic field after such casings are in place. The ferromagnetic formation anamolies are detected in the first step of measuring the field prior to casing placement and further bias characteristics are determined in the second magnetic field measurement step after the casings are placed. Alternately, a conventional gyroscopic survey can be carried out to establish a bias in an already cased bore hole.

Abstract: The present disclosure is directed to both a method and apparatus for providing data dynamically during the drilling of a borehole. This invention can be used with drilling apparatus which is commonly used to drill oil or gas wells, including wells which are vertically drilled or highly deviated wells. The invention provides measures of weight on the drill bit and other forces acting on a drill stem in the vicinity of the drill bit. The present invention is incorporated within the drill stem, which is powered from the surface by a typical rotary drilling rig. The associated drilling apparatus, however, further includes and incorporates a mud motor cooperating with a bent subsection of the sort normally used in drilling a borehole which deviates from the vertical. The downhole element of the invention consists of a subsection which is affixed in the drill stem in the vicinity of the drill bit, and preferably immediately above the drill bit.

Abstract: A method and apparatus are provided for estimating the cross-sectional shape and orientation of an earth borehole and the motion of a tool therein. The method and apparatus involve measuring the distance from the tool to the borehole wall at a plurality of locations around the periphery of the tool and fitting those measured distances to a predetermined shape function using a nonlinear parameter estimation technique to minimize the error between the estimated shape of the borehole and the measured distances. The method and apparatus may be used to estimate elliptical and higher order borehole shapes. Additionally, the method and apparatus may be used while drilling the borehole.

Abstract: The essence of the proposed method resides in that assumed as the datum point of measurement of the well azimuth is an azimuthally stabilized housing of a down-the-hole inclinometer and the magnitude of the azimuth is determined by measuring the angle of rotation of the housing of the down-the-hole instrument (1) round its longitudinal axis, which rotation occurs in response to an azimuthal deviation of the longitudinal axis of a well (5). According to a first embodiment of the proposed device, it comprises a plurality of spring-loaded arcuate elements (3) secured on an external surface (2) of the housing of the down-the-hole instrument (1) so as to form at least three rows, each row consisting of at least three elements (3), each of the latter establishing, together with an internal surface (4) of the well (5), a contact spot (6) whose portion having a greater size (h) is arranged lengthwise the longitudinal axis of the well (5).

Abstract: A borehole survey is conducted at a drilling site S by a so-called Interpolated In-Field Referencing (IIFR) method in which: (a) absolute local geomagnetic field data is obtained by spot measurement of the earth's magnetic field at a local measurement site R which is sufficiently close to the drilling site S that the measurement data is indicative of the earth's magnetic field at the drilling site S but which is sufficiently remote from the drilling site S that the measurement data is unaffected by magnetic interference from the drilling site and other man-made installations; (b) time-varying geomagnetic field data is obtained by combining the absolute local geomagnetic field data with data indicative of variation of the geomagnetic field with respect to time obtained by monitoring variation of the earth's magnetic field with respect to time at a remote monitoring site P1, P2; (c) downhole magnetic field data is obtained by monitoring by means of a surveying instrument the magnetic field in the vicinity of th

Abstract: A switching circuit for use in a subterranean probe for switching between to two modes of operation used to perform a survey of a well borehole. The switching circuit comprises a first voltage bias network which is biased to a predetermined overvoltage criterion; a second voltage bias network which is biased to a predetermined negative voltage criterion; a switch; and a negative voltage blocking diode for blocking the predetermined negative voltage criterion for allowing the first voltage bias network to fully realize the negative voltage criterion.

Abstract: A wellbore survey method and apparatus which includes a gyroscope, wherein the gyroscope has a spin axis, aligned with the instrument axis, and further having two sensitive axis orthogonally related to the spin axis and to each other. In addition, the wellbore survey apparatus contains a drive means, functionally connected with the gyroscope, to rotate the gyro about the instrument axis. The wellbore survey apparatus also contains a set of accelerometers, wherein the sensitive axis are aligned orthogonally to each other, and said drive means is functionally connected to the accelerometers to rotate the accelerometers about the instrument axis. Sensors determine the azimuthal direction of inclination of the wellbore at a first location therein and while traversing from said first location. Attitude references of the wellbore with regard to said first location are determined while the tool is continuously traversing through the wellbore.

Abstract: A method for well borehole survey is set out. A sonde supports X and Y accelerometers and X and & sensors on a rate gyro having a Z axis aligned with the sonde. On a slickline, or within a drill string, the sonde is used to measure four variables, these being G.sub.x and G.sub.y, A.sub.x and A.sub.z. This enables well azimuth and inclination to determined. Measuring depth enables a survey to be made.

Abstract: A method is disclosed for correcting for the distorting effect of cross-axial magnetic interference on the readings of a well survey tool using a reduced number of measurements and measuring locations. A well survey tool connected to a drill string assembly measures the gravitational and distorted terrestrial magnetic fields at two or more axially displaced locations in an axially extending well bore. The measurements are made from two or more different orientations (tool faces) of the tool about the well axis. Initial values for the tool inclination, azimuth and tool face angle are first determined without correction for the cross-axial magnetic interference introduced by the drill string assembly and the survey tool. Measurements made at each location and tool face are referred to the toots coordinate system and variations introduced by the different tool face angles are used to estimate the cross-axial interference. The estimated interference is used to improve the estimate of the azimuth.

Abstract: A dip angle indicator for use in boreholes, and having, an elongated casing, having a diameter to fit down a desired borehole, a sensing chamber, located along the central axis of the casing and defining first and second ends, a linear variable displacement transducer, located along the central axis, and having an operating rod with a free end positioned in the sensing chamber, the rod free end defining a generally conical point, a swing arm located within the sensing chamber, along the central axis, and having a free end defining a generally conical recess, the conical recess receiving the conical point of the transducer rod, movable mounting means mounting the swing arm at one end of the sensing chamber, remote from the transducer, the swing arm extending through the moveable mounting means outside of the chamber, and, weight means mounted on the free end of the swing arm outside the chamber, the weight means being free to move within the casing, whereby to tilt the swing arm within the chamber, and thereby

Abstract: A method for well borehole survey is set out. A sonde supports X and Y accelerometers and X and & sensors on a rate gyro having a Z axis aligned with the sonde. On a slickline, or within a drill string, the sonde is used to measure four variables, these being G.sub.x and G.sub.y, A.sub.x and A.sub.z. This enables well azimuth and inclination to determined. Measuring depth enables a survey to be made.

Abstract: The present invention discloses an MWD system which permits an indirect measurement of the wellbore inclination angle at the drill bit, in situations where it is difficult or expensive to measure that angle directly. The system includes a first inclinometer included as part of a conventional directional sensor, which is located in the bottomhole assembly a relatively large distance above the bit. The first inclinometer provides a measure of the inclination angle .alpha. at point A. The system also includes a second inclinometer, which is provided closer to the drill bit to provide a measure of the inclination angle .beta. at point B. The inclination angles .alpha. and .beta. are used, together with bottomhole assembly configuration information, and other information relating to drilling tendencies, to determine with a reasonable degree of accuracy the inclination angle .theta. of the wellbore at the bit.

Abstract: The present invention relates to a moving device for intervening inside small-diameter pipework. The technical field of the invention lies in constructing measurement apparatus for monitoring pipework and capable of moving along the inside of the pipework in substantially independent manner driven by thrust from the substance conveyed by the pipework acting on the device. According to the present invention, the device comprises a drive piston itself made up of at least two flexible and strong annular tractor cups and defining a sealed section of inside surface, and at least one third centering cup disposed between said two tractor cups. The supports for said cups are interconnected axially in pairs by respective traction cables associated with respective springs surrounding said cables, each spring bearing at each end against said supports of two consecutive cups, and serving to keep said cable under tension.

Abstract: A method for determining orientation of an instrument with respect to earth's gravity. The method includes measuring components of earth's gravity along mutually orthogonal axes. One of the axes is substantially parallel to an axis of the instrument. Tilt of the instrument along two orthogonal axes is measured. One of the tilt axes is substantially parallel to the instrument axis. The instrument is rotated about its axis, and biases of the sensors used to measure the components of earth's gravity perpendicular to the instrument axis are calculated by averaging measurements made by these sensors during rotation. The ratio of gains of these sensors is determined from the range of amplitudes of the output of these sensors during rotation. A roll angle is determined from the bias corrected measurements of components of the earth's gravity perpendicular to the axis. The tilt measurement with respect to the two orthogonal axes is then calibrated by using the calculated roll angle.

Abstract: A method is disclosed for determining wellbore azimuth accurately, notwithstanding the corrupting influence of axial and transverse magnetic field biasing error components.A reliable value of the axial magnetic field component (B.sub.x) is determined by minimizing the vector distance between B (as measured) and its expected value B. Preferably, this is accomplished utilizing a method of radicals to solve a quadratic equation.Given a reliable B.sub.x, the transverse magnetic field components (B.sub.x and B.sub.x) can be determined from taking a number of surveys as the drillstring is rotated about. B.sub.x and B.sub.x can be determined by utilizing the assumption that the transverse magnetic field components should remain invariant as the drillstring is rotated.

Abstract: A compound type cone mirror installed inside a sonde moving up and down in a borehole for observing the whole circumference of the hole wall at an arbitrary depth at a time, a combined mirror for locally observing the hole wall in detail, and an elevating sonde equipped with these mirrors are provided for observing the wall surface of a borehole In the ground. In the compound type cone mirror, a transparent truncated cone block the surface of which is finished by polishing is inserted into a concave portion or pierced hole having the same shape as said truncated cone block and formed coaxially in the axial direction in a transparent column block the surface of which is finished by polishing, and said inserting face is a mirror finished face. Moreover, in the combined mirror, a plane mirror slanted upward at 45.degree. to the axial direction is mounted onto the top face of the truncated cone block or column block of the compound type cone mirror.

Abstract: A bore hole inclinometer device for use in core drilling employing hollow drill rods, and a core barrel, the device having, an elongated casing dimensioned to fit within the hollow drill rods, and having at its lower end an attachment for a core barrel, and at its upper end, an attachment for the wire by which it is hoisted and lowered through the hollow drill rods, an inclinometer within the casing operable to respond to the inclination of the casing to provide an inclination reading, a sensor for sensing the inclination of the casing and providing an inclination signal proportional to the inclination of the casing, an electrical circuit for powering the inclinometer, for receiving the inclination signal, and, an electrical power supply for powering the electrical circuit.

Abstract: A method is provided for deriving wellbore azimuth in a manner which reduces the impact of axial magnetic field errors, which utilizes a plurality of estimates of the axial component of the magnetic field which are combined in a manner which emphasizes the better estimates and deemphasizes the poorer estimates.

Abstract: A method for determining the direction of a borehole during drilling comprises determination of inclination angle .theta. and highside angle .phi. from gravity acceleration (g) measurements and determination of azimuth angle .psi. from magnetic field (B) measurements along with the calculated inclination angle .theta. and highside angle .phi., the determinations being carried out in conventional XYZ-and-NEV coordinate systems coupled by Euler-angle coordinate transformations. In particular g and B are measured at least at two borehole depths such that .phi..sub.i does not equal .phi..sub.i+1, and .psi..sub.i and .psi..sub.i+1 are calculated from B.sub.i =[.phi..sub.i ].sup.T [.theta..sub.i ].sup.T {[.psi..sub.l ].sup.T B.sub.e }+B.sub.p with i as number of measurement, B.sub.e as local earth magnetic field, and B.sub.p as perturbating magnetic field.

Abstract: A measuring tool including a device (4) for measuring the terrestrial magnetic field is inserted in a drill string (2) linking a drilling tool (3) to a surface installation. The method allows to be free from the disturbance affecting the measured terrestrial magnetic field and which is due for example to the drill string. It comprises stopping the tool during the progression thereof in the well in successive stop positions longitudinally spaced out in relation to one another, the angular position of measuring device (4) in these positions being random, and using a statistic calculation method for combining the different measurements and determining the disturbing field.

Abstract: A method for determining the orientation of the axis of a borehole with respect to an Earth-fixed reference coordinate system at a selected series of locations in the borehole, the borehole having a trajectory, and adapted to receive a drill string, comprising defining a model for the influence of magnetic interference from elements of the drill string on the measurement of components of the Earth's magnetic field in the borehole in terms of an unknown vector, a measurement vector, and a measurement matrix relating the unknown vector and the measurement vector; measuring at two or more selected locations along the borehole trajectory at least one of two cross-borehole components of the Earth's gravity field at the selected locations in the borehole, and two cross-borehole components and an along-borehole component of the Earth's gravity field at the selected locations in the borehole; two cross-borehole components and an along-borehole component of the Earth's magnetic field at the selected locations; computi

Abstract: The present method and apparatus are directed to river crossings and the like. A horizontal drilling rig is set up and drills under a body of water or the like. Angular measurement sensors carried at the drill bit provide data periodically which is transmitted from a transmitter at the end of the drill string. Two antennas are deployed, the two being parallel strips spaced equally on the left and right of the right of way. They connect with two receivers. The transmitted angular data is used to determine the location of the drill bit. Progressive determinations of the transmitter enable determination of the trajectory during drilling. The two antennas are used to provide redundant reception of the transmitted signal. In addition to that, a quick reading of lateral drift is obtained by measuring the ratio of the received signals. The two antennas have the form of flat strips which can be deployed across the terrain, over a river, and the like.

Abstract: An attitude control device has a plurality of harmonic drive mechanisms of the hollow type, preferably first and second harmonic drive mechanisms. First and second rotational members are connected to the outputs of the first and second harmonic drive mechanisms. These rotational members have eccentric hollow portions which rotate eccentrically around the rotational axes of the harmonic drive mechanisms. A member to be driven is placed to extend through the eccentric hollow portions such that it is supportedly contacted with the inner surfaces of the eccentric hollow portions. In operation, the eccentric hollow portions are rotated relative to each other, whereby the member to be driven is controllably oriented to a desired direction.The attitude control device can be employed as a drillingdirection control device wherein a rotational drill shaft is supported by inner surfaces of eccentric hollow portions of first and second rotational members.

Abstract: The invention provides a system for precisely guiding the direction of a drill bit. The drill shaft has an orientation sensor that detects deviation of the drilling direction from the desired direction; the drill bit is steerable by preferentially directing flushing fluid at the drilling end; and a fluid modulation means controls the flushing in response to a signal from the orientation sensor. The invention also provides a tiltmeter for detecting deviation from vertical of the axis of rotation of a rotating shaft. A gravity-driven mechanical oscillator, for instance a pendulum, is carried by the rotating shaft, and has a natural oscillation frequency matched to the rotational frequency of the shaft; and a sensor determines the phase relationship of the oscillator relative to the angular position of the shaft, thereby producing a signal indicating the deviation of the shaft from vertical.

Abstract: A magnetic field guidance system for guiding a movable carrier such as a drill assembly with respect to a fixed target includes a pair of magnetic field sources at one location, such as the carrier, and a highly sensitive magnetic field detector at the other location, or target. The first field source is driven by an alternating current to produce a low frequency alternating axial field, while the second source is a magnet which produces a field perpendicular to the axis of the first field. Where the magnetic field sources are mounted on a rotatable drill assembly, the second source may be a permanent magnet which rotates with the drill assembly. The detector may be a fluxgate magnetometer which senses the direction of the target location with respect to the direction of the axial field by determining the deviation from perpendicular of the two magnetic fields at the target location.

Abstract: The angular misalignment of a wellhead is determined by lowering onto the wellhead an assembly having centering means depending from a base plate and level indicator means fixed on top of the plate. The assembly is suspended from the end of a drillstring which carries a level monitoring means.

Abstract: Apparatus and method for positioning a tool, such as a surveying instrument, in the deviated section of a borehole includes a flexible rod and a positioning assembly. The flexible rod extends from the vertical section into the deviated section of the borehole with the tool being connected to the downhole end of the rod. The positioning assembly is connected to the uphole end of the rod for positioning the downhole end of the rod in the deviated section of the borehole when the positioning assembly and the uphole end of the rod are in the vertical section of the borehole. In one embodiment, the positioning assembly is a biasing assembly, such as a weight, for urging the downhole end of the rod and tool into the deviated section. In another embodiment, the positioning assembly is an orienting assembly for rotationally orienting the rod and tool in the borehole as the rod is lowered into the borehole.

Abstract: Apparatus for guiding and steering pipe casing bored and pushed underground by an earth boring machine is disclosed which includes hinge assemblies pivotally connecting a steering head to a front casing. Each hinge assembly includes two pivots. A first pivot has a horizontal pivot axis and a second pivot has a vertical pivot axis. Preferably, the hinge assemblies are compound hinges so that the pivots are carried by a unitary hinge assembly. Actuators are provided which impart an actuation force on the steering head to rotate the steering head about the first and second pivot axes. One of the actuators is provided by slidably mounting one of the hinge assemblies so that the first and second pivot axes of that hinge assembly are compounded and moved unitarily. A second actuator is connected to the steering head to move the steering head about the first pivot axis while the hinge assembly slides to pivot the steering head about the second axis.

Abstract: Apparatus and method for positioning a tool, such as a surveying instrument, in the deviated section of a borehole includes a flexible rod and a positioning assembly. The flexible rod extends from the vertical section into the deviated section of the borehole with the tool being connected to the downhole end of the rod. The positioning assembly is connected to the uphole end of the rod for positioning the downhole end of the rod in the deviated section of the borehole when the positioning assembly and the uphole end of the rod are in the vertical section of the borehole. In one embodiment, the positioning assembly is a biasing assembly, such as a weight, for urging the downhole end of the rod and tool into the deviated section. In another embodiment, the positioning assembly is an orienting assembly for rotationally orienting the rod and tool in the borehole as the rod is lowered into the borehole.

Abstract: A roll sensor is provided for determining the roll angle of a rotatable member. The roll sensor includes a plurality of elements arranged in a predetermined manner, each element having a first state and a second state. A controller controls the respective state of the plurality of elements. A detector detects an output of the elements which are in the first state. A liquid responsive to the rotation of the rotatable member causes the output of at least one of the elements in the first state detected by the detector to be different than the output of the remaining elements in the first state detected by the detector to determine the roll angle of the rotatable member.

Abstract: A borehole deviation monitor comprises a probe body adapted to be lowered in a borehole and including two inclinometers mounted in an orthogonal configuration to provide simultaneous X and Y axis inclination signals indicating the dip angle of the borehole with respect to the vertical and two triaxial magnetometers to provide reference signals indicating the azimuth angle of the borehole. The magnetometers are separated by a predetermined distance along the axis of the probe. A cable takeup winch mechanism is provided to lower the probe body into the borehole by predetermined increments equal to the distance between the two magnetometers. A control and data storage station is connected to the two inclinometers and magnetometers for reading and storing the data collected at each incremental distance and for correcting the azimuth reading given by the top magnetometer by substracting any difference in readings between the two magnetometers at the previous position of the probe.

Abstract: A method for determining the orientation of the axis of a borehole with respect to an earth-fixed reference coordinate system at a location in the borehole comprising the steps of: measuring two cross-borehole components or two-cross-borehole components and an axial component of the earth's gravity field at a location in the borehole; measuring two cross-borehole components of the earth's magnetic field; determining the inclination angle of the borehole axis from the gravity component measurements; determining the highside angle reference of the cross-borehole measured components of the earth's gravity and magnetic fields from the gravity component measurements; determining more than one individual estimate of the azimuthal orientation of the borehole axis from the inclination angle, the highside angle reference and the two measured cross-borehole components of the earth's magnetic field; determining an error indicative parameter for each individual estimate of the azimuthal orientation of the borehole axis;

Abstract: A non-magnetic apparatus is disclosed for finding the deflection of the vertical. That apparatus has a device for finding an instrument spatial angle between a reference direction and an instrument characterization direction, and a device for finding a deflection spatial angle between the instrument characterization direction and a direction along a plumb line. Preferably, the device for finding the instrument spatial angle uses a system of gyroscopes. Preferably, the device for finding the deflection spatial angle uses a pendulum.

Abstract: Apparatus for guiding and steering pipe casing bored and pushed underground by an earth boring machine is disclosed which includes hinge assemblies pivotally connecting a steering head to a front casing. Each hinge assembly includes two pivots. A first pivot has a horizontal pivot axis and a second pivot has a vertical pivot axis. Preferably, the hinge assemblies are compound hinges so that the pivots are carried by a unitary hinge assembly. Actuators are provided which impart an actuation force on the steering head to rotate the steering head about the first and second pivot axes. One of the actuators is provided by slidably mounting one of the hinge assemblies so that the first and second pivot axes of that hinge assembly are compounded and moved unitarily. A second actuator is connected to the steering head to move the steering head about the first pivot axis while the hinge assembly slides to pivot the steering head about the second axis.

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: The radial arm strike rail assembly is a system for measurement of bearings, directions, and stereophotography for geologic mapping, particularly where magnetic compasses are not appropriate. The radial arm, pivoting around a shaft axis, provides a reference direction determination for geologic mapping and bearing or direction determination. The centerable and levelable pedestal provide a base for the radial arm strike rail and the telescoping camera pedestal. The telescoping feature of the radial arm strike rail allows positioning the end of the rail for strike direction or bearing measurement with a goniometer.

Abstract: A wellbore inertial directional surveying system for providing a complete directional survey of an oil or gas well borehole to determine the displacement in all three directions of the borehole path relative to the well head at the surface. The information generated by the present invention is especially useful when numerous wells are drilled to different geographical targets from a single off-shore platform. Accurate knowledge of the path of the borehole allows proper well spacing and provides assurance that target formations are reached. The tool is lowered down into a borehole on the electrical cable. A computer positioned on the surface communicates with the tool via the cable. The tool contains a sensor block which is supported on a single gimbal, the rotation axis of which is aligned with the cylinder axis of the tool and, correspondingly, the borehole.

Abstract: The invention relates to the stereophotogrammetry. A coordinate grid is made in the form of a support (1) carrying a stereophotograph of an image of one or more groups of straight lines (4) converging at a main point (3) and closed lines interconnecting them. The latter, according to the invention, are essentially circles (5) the centers of which are offset relatively the point (3) in one and the same radial direction by an amount of the parallax corresponding to the camera-to-object distance which is represented by the circle circumscribed from this center. The lines (4) and the circles (5) are made in the form of dash lines. The lengths of and the intervals between the dash lines, and the radii of the circles (5) determine the value of a grid division. The dash lines may be made colored and in each group of the lines the dashes have an individual color. The coordinate grid is mainly designed for use in stereoscopes for measuring stereophotographs of an object image.

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: A method of boring a hole in the earth such as for passing under obstacles, not limited, but including roadways, rivers, dikes, canals or other inexcessible areas where it is impossible to trench a ditch including the steps of advancing a rotating drill string in a direction inclined to the earth's surface to establish a borehole, stopping the rotation and advancement of the drill string, aligning the drill pipe so that the drill bit is inclined at an angle relative to the axis of the drill string towards a new direction desired for the borehole, advancing the drill string and drill bit a short distance without rotation, resuming rotation advancement of the drill string for a short distance, sequentially repeating the steps of advancing the rotationally aligned drill string without rotation to move the drill bit in the newly desired direction, followed by rotation with simultaneous advancement until the new direction of drilling is achieved, after which, until a still different direction is desired, drilling

Abstract: A method and apparatus for remotely determining the profile of an inaccessible subterranean passage for example in a mine. An instrument pod is moved through the passage in steps. At each step, a rangefinder scans the wall of the passage and provides to a remote monitor, range measurements from which a profile can be determined. The pod also carries clinometers for determining the orientation of the pod during each profile measurement. The pod also carries a television camera and lights so that the wall of the passage can be visually inspected.

Abstract: Land vehicle navigation apparatus combining an inertial angular rate sensor having a sensitive axis, with an inertial acceleration or tilt sensor having at least two sensitive axes, these sensitive axes having a known relationship to the inertial angular rate sensor's sensitive axis. Also provided is circuitry to accept from an external source an initial input valve (or self initialization, by rotary multiple positioning) of the vehicle's azimuthal orientation angles, roll, pitch, and azimuth, with respect to an Earth-fixed coordinate set as the land vehicle travels over the Earth surface. Changes to the azimuth angle during travel are determined by integration of the output of the inertial angular rate sensor.

Abstract: A method for steering the direction of drilling for oil, gas, or other boreholes drilled in locations such that the level of magnetic interference from nearby magnetic materials or fields is so large that conventional methods using magnetic compass steering tools cannot meet required accuracies. The method is based upon using gyroscope-based survey tools having an inertial angular rate sensor with one or more axes of rate sensitivity and an inertial acceleration or tilt sensor with one or more axes of sensitivity to perform both the normal survey purpose for such tools and the steering function during drilling.The method includes the measurement of initial azimuthal direction, tilt angle, gyro tool face and high side tool face at the beginning of the borehole and the continuous measurement of one or more of these quantities as drilling progresses.

Abstract: A method and apparatus is presented for measuring the azimuth angle of a borehole being drilled, the data for determining the azimuth angle being obtained while the drillstring is rotating.

Abstract: An earth boring tool control system for monitoring the spatial orientation of a remote boring tool (10) and adjusting the path thereof to maintain a predetermined course (22), is comprised of a vertical position detector (26) for determining the elevation of the tool relative to a desired course, including a sensor head member (32) in operative engagement with the tool for establishing a pressure head of fluid characteristic of the vertical disposition of the tool, a pressure sensor member (50) for sensing a differential pressure in response to variations in the height of the pressure head, and a fluid circuit (40, 44) communicating between the sensor head member and the pressure sensor member for transmitting any pressure variations to the sensor member; a horizontal position detector (28) for determining the azimuth of the tool relative to the course, including Hall generators (80, 82) in operative engagement with the tool for developing normalized output signals (90, 92) proportional to deviations in an am

Abstract: .[.When surveying a borehole using an instrument responsive to the earth's magnetic field, a length of non-magnetic drill collar is necessary to house means for measuring the magnetic field in the borehole perpendicular to the direction of the borehole axis. The instrument determines the inclination angle and the highside angle from the gravitation measurements, with these measurements and the magnetic measurements, the azimuth angle is determined. Using the method of this invention a minimum length of non-magnetic material necessary for an accurate measurement may be calculated and used..]. .Iadd.Disclosed are method and apparatus for surveying a borehole including use of a survey instrument for making gravitational measurements from which the inclination and highside angles of the instrument may be determined.